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a. no shutdown b. shutdown c. enable e. no

1. The sender of the digital signal simply varies the signal based on the encoding scheme The receiver interprets the incoming signal according to the same encoding scheme re creating the digits In the figure if the receiver examined the signal at each point with an asterisk the binary code would be 100101011 So if a device wanted to somehow send a set of binary digits to another device and there was a digital circuit between the two it could send the appropriate digital signals over the circuit To achieve a particular bit rate the sender would make sure that the voltage level was at the right level at regular intervals and the receiver would sample the incoming signal at the same rate For instance to achieve 28 kbps the sender would change as necessary the voltage level every 1 28 000th of a second The receiver would sample the incoming digital signal every 1 28 000th of a second as well Converting Analog Voice to Digital Voice The last step in understanding how the PSTN supports voice across a digital PSTN relates to how the PSTN converts the analog electrical signals to digital signals and vice versa To see the need for the conversion examine Figure 15 4 Perspectives onthe PSTN 439 Figure 15 4 Analog Voice Calls Through a Digital PSTN PSTN PCM Codec Converts Analog lt gt Digital Andy s Phone PCM Codec Converts Analog lt gt Digital Local Loop Analog
2. 468 Chapter 15 Remote Access Technologies Table 15 9 Modem Standards Continued Standard Speed Comments V 34 28 8 kbps Backward compatible with V 32bis and V 32 V 42 28 8 kbps Same speed as V 34 but with error correction features V 90 56 kbps downstream 33 kbps Created from two earlier competing upstream standards X2 and K56Flex V 92 56 kbps 33 kbps downstream Connects and finds correct speed more upstream or 48 kbps each direction quickly than V 90 allows modem on hold bis simply means version 2 Figure 15 18 shows the typical topology with ISDN in use for access to an ISP Figure 15 18 ISDN Local Loops and Equipment Andy s Bee PSTN m No PCM Needed on Andy s Digital Local Loop RS 232 Local Loop y Cable Digital BRI 4 las S N Telco ISDN eae i igital T1 Line Switch 1 DSO Channel used Mayberry CO No PCM Needed No Analog Signal E Telco ISDN Switch Raleigh CO Local Loop Digital PRI tho Internal ISDN Card Table 15 10 lists the number of channels for each type of ISDN line and the terminology used to describe them Table 15 10 BRI and PRI B and D Channels Type of Number of Bearer Number of Signaling Interface Channels B Channels Channels D Channels Descriptive Term BRI 2 1 16 kbps 2B D PRI T1 23 1 64 kbps 23B D PRI E1 30 1 64 kbps
3. Host unreachable This code implies that the single destination host is unavailable If Router A has a route to 10 1 2 0 the packet is delivered to Router B However if the web server is down Router B does not get an ARP reply from the web server Router B sends Fred the ICMP Destination Unreachable message with the code host unreachable in response to Fred s packet destined for 10 1 2 14 m Can t fragment This code is the last of the three ICMP unreachable codes that a router might send Fragmentation defines the process in which a router needs to forward a packet but the outgoing interface allows only packets that are smaller than the forwarded packet The router can break the packet into pieces However if Router A or B needs to fragment the packet but the Do Not Fragment bit is set in the IP header the router discards the packet Router A or B sends Fred the ICMP Destination Unreachable message with the code can t fragment in response to Fred s packet destined for 10 1 2 14 m Protocol unreachable If the packet successfully arrives at the web server two other unreachable codes are possible One implies that the protocol above IP typically TCP or UDP is not running on that host This is highly unlikely because most operating systems that use TCP IP use a single software package that provides IP TCP and UDP functions But if the host receives the IP packet and TCP or UDP is unavailable the web server host send
4. Telco Voice Switch Digital T1 Line Barney s 24 Seperate Phone 64 Kbps DS0 Channels Mayberry CO Local 47 Analog Telco Voice Switch Raleigh CO When Andy calls Barney in Raleigh the circuit is set up by the telco Yes Barney moved to Raleigh since the last example And it works It works because the phone company switch in the Central Office CO in Mayberry performs analog to digital A D conversion of Andy s incoming voice When the switch in Raleigh gets the digital signal before sending it out the analog line to Barney s house it reverses the process converting the digital signal back to analog The analog signal going over the local line to Barney s house is roughly the same analog signal that Andy s phone sent over his local line The original standard for converting analog voice to a digital signal is called pulse code modulation PCM PCM defines that an incoming analog voice signal should be sampled 8000 times per second by the analog to digital A D converter A D converters that are used specifically for processing voice are called codecs meaning encoder decoder For each sample the codec measures the frequency amplitude and phase of the analog signal PCM defines a table of possible values for frequency amplitude phase The codec finds the table entry that most closely matches the measured values Along with each entry is an 8 bit binary code which tells the codec wha
5. 1 Which of the following statements describes part of the process of how a transparent bridge makes a decision to forward a frame destined to a unicast MAC address Answer A 2 Which of the following statements describes part of the process of how a LAN switch makes a decision to forward a frame destined to a broadcast MAC address Answer C 3 Which of the following statements best describes what a transparent bridge does with a frame destined to an unknown unicast address Answer A 4 Which of the following comparisons is made by a switch when deciding whether a new MAC address should be added to its bridging table Answer B 5 Which of the following internal switching methods can start forwarding a frame before the entire frame has been received Answer C and D 10 11 12 Chapter9 529 Which of the following internal switching methods must wait to receive the entire frame before forwarding the frame Answer E Which of the following features is determined during autonegotiation between a 10 100 Ethernet card and a switch Answer A and D Which of the following devices would be in the same collision domain as PC1 below Answer A Which of the following devices would be in the same broadcast domain as PC1 below Answer A B and C A network currently has ten PCs with five connected to hub1 and another five connected to hub2 with a cable between the two hubs Fred wants to keep the PCs connected
6. 10 0 0 0 255 255 255 0 is subnetted 3 subnets Cc 10 1 1 0 is directly connected EthernetoO 0 10 1 130 0 is directly connected Seriali c 10 1 128 0 is directly connected Seriald Example 13 3 Yosemite Router Configuration and Exec Commands Yosemite show running config Building configuration Lines ommitted for brevity interface Seriald ip address 10 1 128 252 255 255 255 0 interface Seriali ip address 10 1 129 252 255 255 255 0 interface Ethernet ip address 10 1 2 252 255 255 255 0 lines ommitted for brevity Configuring IP Addresses 375 Example 13 4 Seville Router Configuration and Exec Commands Seville show running config Lines ommitted for brevity interface Seriald ip address 10 1 130 253 255 255 255 0 interface Seriali ip address 10 1 129 253 255 255 255 0 Ethernet ip address 10 1 3 253 255 255 255 0 Lines ommitted for brevity The ip address interface subcommand configures the IP address for each interface as seen in the highlighted portions of the examples Because each interface has an IP address the interface configuration command precedes each ip address command identifying to IOS the interface to which the IP address should be assigned It s that simple Prefix Notation At the end of Example 13 2 Albuquerque you also see the results of the show ip route command The output of the command lists the network 10 0 0 0 fo
7. Do Know This Already Quiz 365 4 What command brings up an interface that previously was administratively disabled a no shutdown b shutdown c enable d up e no disable f disable 5 Imagine that a PC is attached to the same Ethernet as a router The PC makes a DNS request for host name Fred and the PC gets a reply showing IP address 10 1 1 1 What command could be issued on the router to list the information learned in that DNS request and reply a show hosts b show ip hosts c show names d None of the above 6 Imagine that a neighboring router s host name is Hannah Which of these commands could tell you information about the IOS version on Hannah without Telnetting to Hannah a show neighbor b show neighbor Hannah c show cdp d show cdp Hannah e show cdp interface f show cdp neighbor g show cdp neighbor Hannah h show cdp entry hannah i show cdp neighbor detail 366 Chapter 13 Basic Router Configuration and Operation 7 What CDP command s could identify the model of hardware of a neighbor a show neighbors b show neighbors Hannah c show cdp d show cdp Hannah e show cdp interface f show cdp neighbors g show cdp entry hannah h show cdp neighbors detail 8 Imagine that you used a ping command successfully What messages would have been sent by the ping command a ICMP ping b ICMP echo request c ICMP echo management d ICMP query 9 Imagine that you just eras
8. 30B D Foundation Summary 469 Figure 15 19 shows some of the detail of a typical DSL connection Figure 15 19 DSL Connection from the Home IP Network Owned by ISP Andy s PC IP Traffic Split to ISP Ethernet Digital Router Signals gt 4000 Hz Local Loop DSL Router Modem L Analog Voice Split to Voice Switch DTMF Tones Analog Voice Andy s 0 4000 Hz Analog phone Voice Switch w PC Andy s House Mayberry CO Table 15 11 lists the major DSL variants the standard defining that variant the modulation encoding technique speed and distance limitations Table 15 11 DSL Technologies Standards Comparison Modulation Encoding Distance DSL Type Standards Technique Speed Limit Full rate ANSI T1 413 Discrete multitone DMT Downstream speed of 384 18 000 feet ADSL G DMT Issue 2 or carrierless amplitude to 8 Mbps upstream speed phase CAP slower up to 1 024 Mbps G Lite ITU T G 992 1 DMT Downstream speed up to 18 000 feet ITU T G 992 2 1 544 Mbps to 6 Mbps upstream speed up to 640 kbps continues 470 Chapter 15 Remote Access Technologies Table 15 11 DSL Technologies Standards Comparison Continued amplitude modulation TC PAM for both upstream and downstream speed Modulation Encoding Distance DSL Type Standards Technique Speed Limit Very high ETSI and ANSI DMT single carr
9. Answer Fred s configuration implies a subnet with a range of addresses from 10 1 1 1 through 10 1 1 254 so he thinks that Router A s Ethernet interface is in the same subnet However Router A s configuration implies a subnet with addresses from 10 1 1 97 through 10 1 1 126 so Router A does not think that Fred is on the same subnet as Router A s Ethernet Several options exist for fixing the problem You could change the mask used by Fred and Router A s Ethernet to 255 255 255 128 which makes them both reside in the same subnet Referring to Figure A 1 Fred has been configured with IP address 10 1 1 1 mask 255 255 255 240 Router A s Ethernet has been configured with 10 1 1 2 mask 255 255 255 240 Router A s Serial interface uses 10 1 1 129 mask 255 255 255 252 Router B s serial uses 10 1 1 130 mask 255 255 255 252 Router B s Ethernet uses 10 1 1 200 mask 255 255 255 128 and the web server uses 10 1 1 201 mask 255 255 255 128 Is anything wrong with this network What is the easiest thing that could be done to fix it You can assume any working interior routing protocol Answer Router B s configuration implies a subnet with a range of addresses from 10 1 1 129 to 10 1 1 130 on the serial link and 10 1 1 129 to 10 1 1 254 on the Ethernet So the subnets overlap One solution would be to configure Router B and the web server s masks to 255 255 255 192 which would change the subnet so that the valid addresses would
10. Cut through switching sends out the first bytes of the frame before the last bytes of the incoming frame have been received Fragment Free switching is similar to cut through switching in that the frame can be sent before the incoming frame is totally received however Fragment Free processing waits to receive the first 64 bytes to ensure no collisions before beginning to forward the frame Describe how a transparent bridge decides whether it should forward a frame and tell how it chooses the output interface Answer The bridge examines the destination MAC address of a frame and looks for the address in its bridge or address table If found the matching entry tells the bridge which output interface to use to forward the frame If not found the bridge forwards the frame out all other interfaces except for interfaces blocked by spanning tree and the interface in which the frame was received The bridge table is built by examining incoming frames source MAC addresses Define the term collision domain Answer A collision domain is a set of Ethernet devices for which concurrent transmission of a frame by any two of them will result in a collision Bridges switches and routers separate LAN segments into different collision domains Repeaters and shared hubs do not separate segments into different collision domains Name two benefits of LAN segmentation using transparent bridges Answer The main benefits are reduced collisions and
11. Data that includes the Layer 4 protocol header and data given to Layer 4 by the upper layers not including any headers and trailers from Layers 1 to 3 is called what Answer C and G Q amp A 1 Describe the features required for a protocol to be considered connectionless Answer Unordered low overhead delivery of data from one host to another is the service provided in most connectionless protocol services 2 Name at least three connectionless protocols Answer LLC Type 1 UDP IPX and IP are some examples of connectionless protocols Remember Frame Relay X 25 and ATM are connection oriented regardless of whether they define error recovery Chapter6 517 Describe the features required for a protocol to be considered connection oriented Answer Either the protocol must exchange messages with another device before data is allowed to be sent or some pre established correlation between the two endpoints must be defined TCP is an example of a connection oriented protocol that exchanges messages before data can be sent Frame Relay is a connection oriented protocol for which a pre established correlation between endpoints is defined In a particular error recovering protocol the sender sends three frames labeled 2 3 and 4 On its next sent frame the receiver of these frames sets an Acknowledgment field to 4 What does this typically imply Answer Frames through number 3 were received successfully The receiver might have
12. Figure 13 1 Sample Network with Three Routers with Point to Point Serial Links Bugs Daffy 10 1 1 0 10 1 1 251 Fm F 10 1 128 251 a Albuquerque so s1 10 1 130 251 10 1 128 252 10 1 130 253 sO sO eS 10 1 129 0 EF s1 y Yosemite 10 1 129 252 sl Seville 10 1 2 252 10 1 129 253 10 1 3 253 10 1 2 0 10 1 3 0 Sam Emma Elmer Red Basic Administrative Configuration Chapter 7 focused on the configuration process more than the actual configuration commands that happened to be in the chapter Before you configure IP this short section reviews some of the basic commands you typically will configure on any router On most routers you would configure at least the following m A host name for the router m Reference to a DNS so that commands typed on the router can refer to host names instead of IP addresses m Seta password on the console port m Seta password for those Telnetting to the router m Set the enable secret password to protect access to privileged mode m Create a banner stating an appropriate warning depending on the security practices at that company Configuring IP Addresses 371 Example 13 1 shows the output of the show running config command on Albuquerque The functions described in the list have been configured using the commands that are highlighted in the example Example 13 1 Basic Adminsitrative Settings on Albuquerque Router Albuquerque show running config Building configuration
13. Integrated Services Digital Network 447 many more bytes to you than you send to it By using modem standards that use asymmetric rates the maximum rate can be increased for the direction of data that needs the additional bandwidth V 92 the latest of these standards has some very interesting features You can configure it to transfer data at symmetric 48 kbps rates or asymmetric rates equivalent to V 90 s 56 kbps downstream and 33 kbps upstream It also allows the modem to recognize call waiting signals from the telco letting you take or make a call while keeping your modem connection up for a short time Technically you are not sending data and talking at the same time because data transmission is put on hold but it is a very convenient feature Analog Modem Summary Modems have the great advantage of being the most pervasively available remote access technology The history of modems is long with modems growing to be a very reliable choice for remote access Speeds have improved over the years with compression technology increasing the effective throughput to beyond 100 kbps Modems provide a Layer 1 service of delivering a bit stream between the two endpoints on the dialed circuit To pass IP traffic an appropriate data link protocol must be used typically PPP The biggest negatives about using modems include their relatively low speed and the fact that you cannot use the phone at the same time as you send data I
14. Open User is getting into New York now based on telnet NewYork command User Access Verification Password NewYork gt User can now type commands on New York NewYork gt NewYork gt NewYork gt Note User pressed Ctrl Shift 6 and then x Cincy show sessions This command lists suspended Telnet sessions Conn Host Address Byte Idle Conn Name 1 milwaukee 10 1 4 252 1 milwaukee 2 NewYork 10 1 6 253 0 NewYork Cincy where where does the same thing Conn Host Address Byte Idle Conn Name 1 milwaukee 10 1 4 252 1 milwaukee 2 NewYork 10 1 6 253 1 NewYork Cincy resume 1 Resume connection 1 see show session to Milwaukee Resuming connection 1 to milwaukee Milwaukee gt User can type commands on Milwaukee Milwaukee gt Milwaukee gt Note User pressed Ctr1 Shift 6 and then x User wants to go back to Cincy Cincy WOW User just pressed Enter and resumes the last Telnet Resuming connection 1 to milwaukee Milwaukee gt Milwaukee gt Milwaukee gt Note User pressed Ctr1 Shift 6 and then x Tired of Milwaukee again can t imagine why Cincy disconnect 1 No more need to use Milwaukee Telnet terminated Closing connection to milwaukee confirm User presses Enter to confirm Cincy Resuming connection 2 to NewYork IP Troubleshooting Features 391 Example 13 10 Telnet Suspensions Continued Pressing Enter resumes most recently suspended active Telnet NewYork gt N
15. Seville configure terminal Enter configuration commands one per line End with CNTL Z Seville config interface serial 1 Seville config if shutdown Seville config if Z Seville show ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 E1 OSPF external type 1 E2 OSPF external type 2 E EGP i IS IS L1 IS IS level 1 L2 IS IS level 2 ia IS IS inter area candidate default U per user static route o ODR P periodic downloaded static route Gateway of last resort is not set 10 0 0 0 24 is subnetted 2 subnets 03 10 1 3 0 is directly connected Ethernet C 10 1 130 0 is directly connected Serial Seville show ip interface brief Interface IP Address OK Method Status Protocol Serial 10 1 130 253 YES manual up up Seriali 10 1 129 253 YES manual Administratively down down Ethernet 10 1 3 253 YES manual up up Seville configure terminal Enter configuration commands one per line End with CNTL Z Seville config interface serial 1 Seville config if no shutdown Seville config if Z In the example after the shutdown command under interface serial 1 the route connected to serial 1 10 1 129 0 mask 255 255 255 0 was removed from the routing table leaving only two entries Also the output of the show ip interfaces brief command lists a status
16. data over cable standards treats data going toward the home differently than data coming from the home In fact CATV terminology refers to the data going toward the home as downstream data and data from the home as upstream data Downstream data uses standards that are consistent with some of the standards for sending digital video over cable In fact you can think of the downstream data as being sent over another TV channel For downstream data the data over cable standards takes advantage of the fact that the signals are broadcast to all subscribers in a section of the cable plant Just like the TV channels signals go to every home the signals for the downstream data go to every home In many ways the concepts are similar to an Ethernet broadcast domain When a broadcast Ethernet frame is sent everyone in the broadcast domain receives the frame With downstream cable transmissions not just broadcast frames but all data is broadcast to all receivers Yes the data that you receive over the web actually could be captured with a network analysis tool by one of your neighbors Because every home in a part of the cable network receives the same data channel some form of addresses must be used so that only the correct device tries to process incoming data For Cable Modems 463 instance your PC does not need to process any data being sent to your neighbor s PC So CATV standards call for the use of a data link protocol called Multimedi
17. information between ISPs worldwide today and between ISPs and their customers as need be Routing protocols that are best used to distribute routes between companies and organizations such as BGP are called exterior routing protocols Routing protocols designed to distribute routing information inside a single organization are called interior routing protocols The comparison is like the U S Department of Transportation DOT versus the local government s transportation department The U S DOT plans the large interstate highways but it could care less that someone just sold a farm to a developer and the local government has given the developer the approval to pave a new street so that he can build some houses The U S DOT could be compared to exterior routing protocols they care about overall worldwide connectivity but they could care less when a single company adds Routing Protocol Overview 409 a new LAN and a new subnet However the interior routing protocols do care so when the packet gets to the company all the routers will have learned about any new subnets and the packet can be delivered successfully This section focuses on how to compare the interior IP routing protocols because there are several on the INTRO exam and there are many points of comparison Table 14 2 lists some of the major comparison points Table 14 2 Major Comparison Points Between Interior Routing Protocols Point of Comparison Description Ty
18. password cisco login I end Albuquerque show ip route Codes C connected S static I IGRP R RIP M D EIGRP EX EIGRP external O OSPF IA N1 OSPF NSSA external type 1 N2 Should ve taken a left turn here This is Albuquerque mobile B BGP OSPF inter area OSPF NSSA external type 2 C continues 374 Chapter 13 Basic Router Configuration and Operation Example 13 2 Albuquerque Router Configuration and Exec Commands Continued E1 OSPF external type 1 E2 OSPF external type 2 E EGP i IS IS L1 IS IS level 1 L2 IS IS level 2 ia IS IS inter area candidate default U per user static route o ODR P periodic downloaded static route Gateway of last resort is not set 10 0 0 0 24 is subnetted 3 subnets Cc 10 1 1 0 is directly connected EthernetO Cc 10 1 130 0 is directly connected Seriali Cc 10 1 128 0 is directly connected Seriald Albuquerque terminal ip netmask format decimal Albuquerque show ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 E1 OSPF external type 1 E2 OSPF external type 2 E EGP i IS IS L1 IS IS level 1 L2 IS IS level 2 ia IS IS inter area candidate default U per user static route o ODR P periodic downloaded static route Gateway of last resort is not set
19. 0001 or adding boot system rom to the configuration file and copying it to the startup configuration file To set the configuration register to hex 2101 which would yield binary 0001 in the boot field the config register 0x2101 global configuration command would be used A third method not mentioned in the chapter includes removing the Flash memory in a router and then reloading What is the process used to update the contents of Flash memory so that a new IOS ina file called c4500 d mz 120 5 bin on TFTP server 128 1 1 1 is copied into Flash memory Answer copy tftp flash The other details namely the IP address of the TFTP server and the filename are requested through prompts to the user Name three possible problems that could prevent the command boot system tftp c2500 j 1 112 14 bin 128 1 1 1 from succeeding Answer The possible reasons include 128 1 1 1 is not accessible through the network there is no TFTP server on 128 1 1 1 the file is not in the TFTP default directory the file is corrupted a different boot command could precede this boot command in the configuration file meaning that the IOS referenced in the first boot command would be used instead Two different IOS files are in a router s Flash memory one called c2500 j 1 111 3 bin and one called c2500 j 1 112 14 bin Which one does the router use when it boots up How could you force the other IOS file to be used Without looking at the router configuration what
20. 1 0 0 has been assigned by the NIC The maximum number of hosts per subnet is 100 2 Assign IP addresses to the PCs as well 3 Assign addresses for the switches near R1 for management purposes Assume that a single VLAN is used on the switches near Router 1 R1 Tables 16 1 and 16 2 are provided as a convenient place to record your IP subnets and IP addresses when performing the planning tasks for this scenario Figure 16 1 Scenario Network Diagram aS ff Server 1 g Server 2 484 Chapter 16 Final Preparation Table 16 1 Part A IP Subnet and IP Address Planning Chart Location of Subnet Network Geographically Subnet Mask Subnet Number R1 Ethernet R2 Ethernet R3 Ethernet Serial between R1 and R2 Serial between R1 and R3 Serial between R2 and R3 Table 16 2 Part A IP Address Planning Chart Host Address PC11 PC12 PC13 PC21 PC31 PC32 SW1 SW2 SW3 R1 E0 R1 SO R1 S1 R2 E0 R2 SO R2 S1 R3 E0 R3 S0 R3 S1 Server 1 Server 2 Server 3 Scenario Part A Planning 485 Solutions to Part A Planning It s a good idea to keep the design as simple as possible without making it so simple that it will not be useful as the network evolves In this case any subnet mask with at least 7 host bits would work including the easy mask of 255 255 255 0 Any
21. 2 Do I Know This Already Quiz 1 Which of the following protocols are examples of TCP IP transport layer protocols Answer D and F Which of the following protocols are examples of TCP IP network interface layer protocols Answer A and G Which OSI layer defines the functions of logical network wide addressing and routing Answer C Which OSI layer defines the standards for cabling and connectors Answer A Which OSI layer defines the standards for data formats and encryption Answer F Which of the following terms are not valid terms for the names of the seven OSI layers Answer C and E The process of HTTP asking TCP to send some data and make sure that it is received correctly is an example of what Answer B 500 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 8 The process of TCP on one computer marking a segment as segment 1 and the receiving computer then acknowledging the receipt of segment 1 is an example of what Answer B 9 The process of a web server adding a HTTP header to a web page followed by adding a TCP header then an IP header and then data link header and trailer is an example of what Answer A 10 Which of the following terms is used specifically to identify the entity that is created when encapsulating data inside data link headers and trailers Answer D Q amp A 1 Name the seven layers of the OSI model Answer Applicatio
22. 398 Chapter 13 Basic Router Configuration and Operation Table 13 9 summarizes the key naming commands in IOS Table 13 9 IP Naming Commands Function Command Options Tell IOS to use a DNS Configure the ip domain lookup global configuration command Configure IP addresses of name servers Configure the ip name server svr1 svr2 global configuration command Configure static host names Use the ip host name address command List current host name information Use the show hosts exec command Table 13 10 summarizes the commands related to Telnet Table 13 10 Telnet Command Options Function Command Options Telnet to another device Use the telnet exec command Just type the host name or IP address from exec mode Suspend a Telnet session Press the key sequence Ctrl Shift 6 then x Discover currently Use the where exec command suspended Telnet session Use the show sessions exec command Resume a suspended Telnet Use the resume command with no parameter to reconnect to session the most recently suspended Telnet session Use the resume x command where x is the number of the suspended Telnet session based on the output of show sessions Just press Enter in exec mode to resume to the most recently suspended Telnet session Terminate a suspended Resume connection and log out using the quit command Telnet session Use the disconnect command on the router you Te
23. A Sections 10 Given the IP address 220 8 7 100 and the mask 255 255 255 240 what is the broadcast address Answer The broadcast address is 220 8 7 111 The binary algorithm is shown in the table that follows Address 220 8 7 100 1101 1100 0000 1000 0000 0111 0110 0100 Mask 255 255 255 240 1111 1111 1111 1111 1111 1111 1111 0000 Result 220 8 7 96 1101 1100 0000 1000 0000 0111 0110 0000 Broadcastaddress 220 8 7 111 1101 1100 0000 1000 0000 0111 0110 1111 11 Given the IP address 134 141 7 11 and the mask 255 255 255 0 what are the assignable IP addresses in this subnet Answer The subnet number is 134 141 7 0 and the subnet broadcast address is 134 141 7 255 The assignable addresses are all the addresses between the subnet and broadcast addresses namely 134 141 7 1 to 134 141 7 254 12 Given the IP address 193 193 7 7 and the mask 255 255 255 0 what are the assignable IP addresses in this subnet Answer The subnet number is 193 193 7 0 and the network broadcast address is 193 193 7 255 The assignable addresses are all the addresses between the network and broadcast addresses namely 193 193 7 1 to 193 193 7 254 13 Given the IP address 200 1 1 130 and the mask 255 255 255 224 what are the assignable IP addresses in this subnet Answer The subnet number is 200 1 1 128 and the subnet broadcast address is 200 1 1 159 The assignable addresses are all the addresses between the subnet and broadca
24. Current configuration 872 bytes version 12 2 service timestamps debug uptime service timestamps log uptime no service password encryption hostname Albuquerque enable secret 5 1 J3Fz QaEYNIiI2aMu 3Ar q0Xm ip name server 10 1 1 100 ip name server 10 1 2 100 interface Serial interface Seriali interface Ethernet no ip http server banner motd C Should ve taken a left turn here This is Albuquerque C line con 0 password cisco login exec timeout 00 line aux 0 line vty 4 password cisco login loggiing synchronous None of the commands highlighted in Example 13 1 is required for the router to route IP but the commands are generally useful in real networks Of note to make the router ask for a password at the console you need the login console subcommand the password console 372 Chapter 13 Basic Router Configuration and Operation subcommand tells the router what password is required at the console Similar logic applies to the login and password vty subcommands And although you do not have to refer to a name server when you do you typically refer to at least two because most networks have at least two name servers for redundancy and availability When configuring the enable secret command you type the password just like you want the user to type it when logging in to the router however the IOS changes the value that is saved in the configuration For instance
25. Layer 1 QPSK and QAM 16 OSI Layer 2 MCNS MAC and IEEE 802 2 LLC Multiplexing used Time division multiple access TDMA Speed 320 kbps to 10 Mbps The remote access technologies in this chapter provide services at Layer 1 and possibly Layer 2 of the OSI model TCP IP and all the associated higher layer protocols TCP UDP HTTP FTP Telnet DNS DHCP and so on can run over any of these access technologies the differences lie in what is done at Layers 1 and 2 Figure 15 21 outlines the protocols used by each Figure 15 21 Applications TCP or UDP IP PPP Modem Standards v x Applications TCP or UDP ATM Ethernet xDSL Standards The OSI Model and Remote Access Technologies Applications TCP or UDP IP PPP ISDN I 430 Standards Applications TCP or UDP IP IEEE 802 2 MCNS MAG Upstream Downstream QPSK QAM 16 QAM 64 QAM 256 Foundation Summary 473 Table 15 14 lists some of the main points for comparison of these technologies Comparison points are always good material for exam questions Table 15 14 Comparison of Modems ISDN DSL and Cable Analog Modems ISDN DSL Cable Modems Transport Telco line Telco line Telco line CATV cable Supports symetric Yes Yes Yes No speeds Supports asymmetric Yes No Yes Yes speeds Speed ranges Less than 64
26. Protocol CDP discovers basic information about neighboring routers and switches without needing to know the passwords for the neighboring devices CDP supports any LAN HDLC Frame Relay and ATM interface in fact it supports any interface that supports the use of SNAP headers The router or switch can discover Layer 2 and Layer 3 addressing details of neighboring routers without even configuring that Layer 3 protocol this is because CDP is not dependent on any particular Layer 3 protocol When Cisco first developed the proprietary CDP it was used mainly between routers Today most Cisco products support CDP including Cisco switches and Cisco IP Phones Devices that support CDP advertise their own information and learn information about others by listening for their advertisements On media that support multicasts at the data link layer CDP uses multicast on other media CDP sends a copy of the CDP update to any known data link addresses So any CDP supporting device that shares a physical medium with another CDP supporting device can learn about the other device IP Troubleshooting Features 393 CDP discovers several useful details from the neighboring device m Device identifier Typically the host name m Address list Network and data link addresses Port identifier Text that identifies the port which is another name for an interface Capabilities list Information on what type of device it is for instance a router
27. Route Routing Update Subnet Metric 10 1 1 0 1 nn ay 0 1 2 1 An 10 1 3 0 yg z 255 255 255 0 A s Bo 10 1 1 0 255 255 255 0 B s Routing Table IP Subnet Mask Next Router Output Interface 10 1 1 0 255 255 255 0 10 1 2 1 Serial 0 412 Chapter 14 Introduction to Dynamic Routing Protocols Note that Router A advertises the route to its LAN subnet to Router B The update includes only the subnet number and a metric Router B then adds a route to its routing table but the route has more information in it than did the routing update itself When B received the update it came in interface Serial0 so Router B considers Serial0 to be the correct outgoing interface The update came from IP address 10 1 2 1 so Router B considers that IP address to be the next hop IP address Also if the distance vector update does not include the subnet mask as in the figure Router B assumes that Router A uses the same mask that it does As it turns out these routers would not support VLSM because if Router A used a different subnet mask than Router B B would make a wrong assumption about the mask The fact that the routing protocol in this example does not transmit mask information also makes it a classful routing protocol For these examples assume that all routers are using the same subnet mask in this network specifically 255 255 255 0 If it seems simple then you understand it well distance vector protocols firs
28. The DSLAM gives the analog voice signal the frequency range between 0 Hz and 4000 Hz to a voice switch The voice switch treats that signal just like any other analog voice line the switch listens for DTMF tones creates a circuit and does PCM encoding to convert the analog signal The DSLAM does not pass the data traffic into the PSTN however The DSLAM forwards the data traffic to a router owned by the ISP providing the service in this figure Alternately the DSLAM can forward the data traffic over an IP network ultimately reaching a router inside a corporate network Notice that the ISP s router actually is depicted as being resident in the local telco CO that is true in many cases However many people use an ISP that does not happen to be the local telco To support DSL the ISP works with the local telco to install some of the ISP s gear in the CO a process called co location or co lo for short The local telco DSLAM forwards and receives the IP packets to and from the ISP router while the telco maintains control over the local voice traffic Typically the consumer requests high speed Internet access using DSL from an ISP the ISP charges the customer for the service and then the ISP pays the local telco some cut of the fee DSL Standards DSL comes in many flavors to meet different needs For instance DSL has limits on how long the local loop can be the length of the local loop is simply the length of the combined c
29. Working ping and One Failing ping Sending 5 100 byte ICMP Echos to 10 1 128 252 timeout is 2 seconds Success rate is 100 percent 5 5 round trip min avg max 4 4 8 ms Albuquerque ping 10 1 2 252 Type escape sequence to abort Sending 5 100 byte ICMP Echos to 10 1 2 252 timeout is 2 seconds Success rate is 0 percent 0 5 The ping command sends a packet to the stated destination address The TCP IP software at the destination then replies to the ping packet with a similar packet The ping command sends the first packet and waits on the response If a response is received the command displays an exclamation mark If no response is received within the default timeout of 2 seconds the ping command displays a period The IOS ping command sends five of these packets by default In Example 13 8 the ping 10 1 128 2 command works but the ping 10 1 2 252 command does not The first ping command works because Albuquerque has a route to the subnet in which 10 1 128 2 resides subnet 10 1 128 0 However the second ping to 10 1 2 252 does not work because the subnet in which 10 1 2 252 resides subnet 10 1 2 0 is not connected to Albuquerque so Albuquerque does not have a route to that subnet So none of the five ping packets works resulting in five periods in the output of the ping command The ping would have worked if a routing protocol had been implemented successfully in this network Had these routers been using
30. a 64 kbps channel 3 Define what a voice codec does and explain why a PCM codec needs 64 kbps for a single voice call Answer Voice codecs code and decode voice signals converting from analog to digital and digital to analog A PCM codec samples the analog signal 8000 times per second generating an 8 bit code to represent each sample So 64 000 bits are needed for a single second of voice 4 Two terms were shortened and combined to first create the word modem Identify those two words and describe what each word means Answer The term modem is formed as a combination of the words modulation and demodulation Modulation means to vary or change a wave form to encode information A modem varies an analog electrical signal to encode information representing binary digits onto an analog signal Modulation refers to the creation of the analog signal based on a string of bits and demodulation simply refers to a modem performing the reverse process upon receiving the analog signal 5 Define what the terms symmetric and asymmetric mean in relation to modem specifications Also explain why asymmetric might be a better option Answer Symmetric means that the speed in each direction of flow is the same whereas asymmetric means that the speed in one direction is faster than the other Asymmetric speeds might be a good choice because typical traffic flows require a much greater amount of data to flow in one direction typically from a
31. as a data link layer unit over a transmission medium Can also be called an L2PDU full mesh A term describing a network in which devices are organized in a mesh topology with each network node having either a physical circuit or a virtual circuit connecting it to every other network node A full mesh provides a great deal of redundancy but because it can be prohibitively expensive to implement it usually is reserved for network backbones hash A mathematical formula applied to some input value for which it is difficult to recreate the input value even if you know the results of the formula Hashes are useful for transmission of passwords because even if intercepted the hashed representation of a password cannot easily be used to find the original password HDLC High Level Data Link Control A bit oriented synchronous data link layer protocol that specifies a data encapsulation method on synchronous serial links using frame characters and checksums head end The upstream transmit end of a CATV installation holddown A state into which a route is placed so that routers neither advertise the route nor accept advertisements about the route for a specific length of time the holddown period Holddown is used to flush bad information about a route from all routers in the network A route typically is placed in holddown when a link in that route fails host address The IP address assigned to a network card on a computer IP 583 host A co
32. be between 10 1 1 193 and 10 1 1 254 550 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 23 What are the valid private IP network numbers according to RFC 1918 Answer Network 10 0 0 0 Class B networks that from 172 16 0 0 through 172 31 0 0 and Class C networks beginning with 192 168 24 How large are IPv6 addresses Answer 128 bits long 25 How does CIDR help reduce the size of Internet routing tables Answer By using a routing protocol that exchanges the mask as well as the subnet network number a classless view of the number can be attained By advertising many networks as a single route the routing table can be shortened For instance 198 0 0 0 8 198 0 0 0 mask 255 0 0 0 defines a set of addresses whose first 8 bits are equal to decimal 198 Instead of the more than 65 000 routes needed to list a route for each class C network that starts with 198 CIDR allows those routes to be represented by a single route Chapter 13 Do I Know This Already Quiz 1 Which of the following commands is valid for the configuration of IP address 10 1 1 1 mask 255 255 255 0 Answer C 2 Which of the following must be true before Cisco IOS Software adds a connected route to the routing table Answer A and E The router adds the subnet number of the directly connected interface to the routing table after the IP address is configured The interface must be operational before the route
33. calculate the subnet number without binary math The magic number is 256 224 32 Octet 1 2 3 Comments Address 200 1 1 Mask 255 255 255 Interesting octet is the fourth octet magic 256 224 32 Subnet number 200 1 1 128 is the closest multiple of the magic number not greater than 130 First address 200 1 1 Add 1 to the last octet of the subnet number Broadcast 200 1 1 Subnet magic 1 Last address 200 1 1 Subtract 1 from broadcast 6 Given the IP address 220 8 7 100 and the mask 255 255 255 240 what is the subnet number Answer The answer is 220 8 7 96 The table that follows shows the subnet chart to help you learn the way to calculate the subnet number without binary math The magic number is 256 240 16 Octet 1 2 3 Comments Address 220 8 7 Mask 255 255 255 Interesting octet is the fourth octet Subnet number 220 8 7 96 is the closest multiple of the magic number not greater than 100 First address 220 8 7 Add 1 to the last octet Broadcast 220 8 7 Subnet magic 1 Last address 220 8 7 Subtract 1 from broadcast 7 Chapter12 545 Given the IP address 134 141 7 11 and the mask 255 255 255 0 what is the subnet broadcast address Answer The broadcast address is 134 141 7 255 The binary algorithm is shown in the table that follows Address 134 1
34. choice of mask between 255 255 224 0 and 255 255 255 128 would have allowed for 6 subnets and 100 hosts per subnet Table 16 3 shows one solution for the subnet numbers chosen using mask 255 255 255 128 with Table 16 4 showing some sample IP address assignments Table 16 3 Part A The Completed IP Subnet Planning Chart Location of Subnet Network Geographically Subnet Mask Subnet Number R1 Ethernet 255 255 255 128 163 1 1 128 R2 Ethernet 255 255 255 128 163 1 2 128 R3 Ethernet 255 255 255 128 163 1 3 128 Serial between R1 and R2 255 255 255 128 163 1 12 128 Serial between R1 and R3 255 255 255 128 163 1 13 128 Serial between R2 and R3 255 255 255 128 163 1 23 128 Table 16 4 Part A The Completed IP Address Planning Chart Host Address PC11 163 1 1 211 PC12 163 1 1 212 PC13 163 1 1 213 PC21 163 1 2 221 PC31 163 1 3 231 PC32 163 1 3 232 SW 163 1 1 211 SW2 163 1 1 212 SW3 163 1 1 213 R1 E0 163 1 1 201 R1 SO 163 1 12 201 R1 S1 163 1 13 201 R2 E0 163 1 2 202 R2 SO 163 1 12 202 continues 486 Chapter 16 Final Preparation Table 16 4 Part A The Completed IP Address Planning Chart Continued Host Address R2 S1 163 1 23 202 R3 E0 163 1 3 203 R3 S0 163 1 13 203 R3 S1 163 1 23 203 Server 1 163 1 1 1 Server 2 163 1 1 2 Server 3 163 1 2 3 As long as the numbers are in the right subnet the actual IP
35. command could be used to discover which file was used for the latest boot of the router Answer The first IOS file listed in the show flash command is the one used at reload time unless a boot system command is configured The configuration command boot system flash c2500 j 1 112 14 bin would override the IOS s decision to look for files in order in Flash memory show version is the command used to display the filename of IOS 524 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections for the latest reload of a router The show version output tells you the version as well as the name of the file that was used at last reload time It is particularly difficult to find in the output of the command 27 Is the password required at the console the same one that is required when Telnet is used to access a router Answer No The Telnet virtual terminal password is not the same password although many installations use the same value 28 Which IP routing protocols could be enabled using setup Answer RIP and IGRP 29 Name two commands used to view the configuration to be used at the next reload of the router Which one is a more recent addition to IOS Answer show config and show startup config show startup config is the newer one and hopefully is easier to remember 30 Name two commands used to view the configuration that currently is used in a router Which one is a more recent addition to IOS A
36. devices on one or more LANs that are configured using management software so that they can communicate as if they were attached to the same wire when in fact they are located on a number of different LAN segments Because VLANs are based on logical instead of physical connections they are extremely flexible VoIP Voice over IP The capability to carry voice over an IP based Internet VoIP enables a router to carry voice traffic for example telephone calls and faxes over an IP network well known port A port number reserved for use by a particular application The use of well known ports allows a client to send a TCP or UDP segment to a server to the correct destination port for that application windowing The term window represents the number of bytes that can be sent without receiving an acknowledgment Windowing is the dynamic raising and lowering of the window to control the flow of data in a network WWW World Wide Web A large client server network of Internet servers providing hypertext and other services based on HTML and HTTP to terminals running client applications such as a browser zero subnet When subnetting a Class A B or C network two subnet numbers are discouraged from use the zero subnet is one of these two subnets It is the subnet number for which the subnet bits all have a value of binary 0
37. for Example 13 1 I typed enable secret cisco and the router changed cisco to a hashed value that cannot be converted back to cisco Two other things that you might want to configure habitually on routers are the console timeout and the synchronization of unsolicited messages In some cases you want the router to exit the user from the console after a period of inactivity In other cases you do not want the console disabled at all because of inactivity The exec timeout minutes seconds command sets the inactivity timeout Also unsolicited informational messages and output from the IOS debug command both show up at the console by default These same messages can be seen at the aux port or when Telnetting into a router by using the terminal monitor command The logging synchronous line subcommand tells the router not to interrupt the output of a show command with these unsolicited messages letting you read the output of the command that you typed before the router displays the other messages logging synchronous can make your life a lot easier when using a router Configuring IP Addresses Before you configure IP address you first must decide what IP addresses to configure Figure 13 1 not only outlined the network diagram but it also listed the IP addresses chosen for the network In this case network 10 0 0 0 hs been subnetted with six subnets and a mask of 255 255 255 0 After you have chosen the IP addresses and masks configuration is simp
38. got more sophisticated Phones evolved to have a rotary dial on them so you could just pick up the phone and dial the number you wanted to call Later 12 digit keypads replaced the dial so that you could simply press the numbers For those of you who do not remember phones with dials on them it would have taken you 20 seconds to dial a number that had lots of 8s 9s and Os in them so a keypad was a big timesaver The PSTN also evolved to use digital signals instead of analog signals inside the core of the PSTN By using digital signals instead of analog the PSTN could send more voice calls over the same physical cables which in turn allowed it to grow while reducing the per call minute cost So what is a digital signal Digital signals represent binary numbers Electrically digital signals use a defined set of both positive and negative voltages which in turn represent 438 Chapter 15 Remote Access Technologies either a binary 0 or a binary 1 Encoding schemes define the rules as to which electrical signals mean a binary 0 and which ones mean a binary 1 The simplest encoding scheme might be to represent a binary 1 with 5V and a binary 0 with 5V much more sophisticated encoding schemes are used today Figure 15 3 shows an example of a graph of a digital signal over time using the basic encoding scheme that was just described Figure 15 3 Example of a Digital Signal with a Simple Encoding Scheme Voltage
39. how many hosts per subnet respectively Answer E Class B networks imply 16 network bits the mask implies 7 host bits 7 binary Os in the mask leaving 9 subnet bits 2 2 yields 510 subnets and 2 2 yields 126 hosts per subnet Chapter 12 541 If mask 255 255 255 240 were used with a Class C network how many subnets could exist with how many hosts per subnet respectively Answer B Class C networks imply 24 network bits the mask implies 4 host bits 4 binary Os in the mask leaving 4 subnet bits 24 2 yields 14 subnets and 24 2 yields 14 hosts per subnet Which of the following IP addresses would not be in the same subnet as 190 4 80 80 mask 255 255 255 0 Answer E 190 4 80 80 mask 255 255 255 0 is in subnet 190 4 80 0 broadcast address 190 4 80 255 with a range of valid addresses between 190 4 80 1 of 190 4 80 254 Which of the following IP addresses would not be in the same subnet as 190 4 80 80 mask 255 255 240 0 Answer F 190 4 80 80 mask 255 255 240 0 is in subnet 190 4 80 0 broadcast address 190 4 95 255 with a range of valid addresses of 190 4 80 1 through 190 4 95 254 Which of the following IP addresses would not be in the same subnet as 190 4 80 80 mask 255 255 255 128 Answer D E and F 190 4 80 80 mask 255 255 255 128 is in subnet 190 4 80 0 broadcast address 190 4 80 127 with a range of valid addresses of 190 4 80 1 through 190 4 80 126 Which of the following subnet mas
40. is added 3 Which of the following represents the same ideas as mask 255 255 240 0 Answer C The answers all use prefix notation which represents the subnet mask by stating the number of binary 1s in the mask 4 What command brings up an interface that previously was administratively disabled Answer A shutdown disables the interface and no shutdown brings it back up 10 Q amp A Chapter 13 551 Imagine that a PC is attached to the same Ethernet as a router The PC makes a DNS request for host name Fred and the PC gets a reply showing IP address 10 1 1 1 What command could be issued on the router to list the information learned in that DNS request and reply Answer D The show hosts command lists the host name configured in the router or names learned by the router from the DNS as a result of a command on the router using the name The router does not learn about names as a result of DNS requests from an end user Imagine that a neighboring router s host name is Hannah Which of these commands could tell you information about the IOS version on Hannah without Telnetting to Hannah Answer H and I CDP discovers information about neighbors show cdp gives you several options that display more or less information depending on the parameters used What CDP command s could identify the model of hardware of a neighbor Answer F G and H Imagine that you used a ping command successfully What messages would have been s
41. kbps per 56 kbps to 320 kbps to 40 56 kbps B channel 2 Mbps Mbps Degrades under higher No No No Yes loads Supports IP and Yes Yes Yes Yes associated higher layer protocols Allows concurrent No Yes Yes Yes voice and data Always on No No Yes Yes Local loop distance No No Yes distance No issues varies 474 Chapter 15 Remote Access Technologies O amp A As mentioned in the introduction you have two choices for review questions The questions that follow give you a bigger challenge than the exam itself by using an open ended question format By reviewing now with this more difficult question format you can exercise your memory better and prove your conceptual and factual knowledge of this chapter The answers to these questions are found in Appendix A For more practice with exam like question formats including questions using a router simulator and multiple choice questions use the exam engine on the CD 1 What do ISDN BRI and PRI stand for 2 How many bearer channels are in a BRI What about a PRI in North America What about a PRI in Europe 3 Define what a voice codec does and explain why a PCM codec needs 64 kbps for a single voice call 4 Two terms were shortened and combined to first create the word modem Identify those two words and describe what each word means 5 Define what the terms symmetric and asymmetric mean in relation to modem specifications Also explain why asymm
42. lower speeds than DSL or cable Digital Subscriber Line Any two computers using compatible modems could communicate with each other Those computers might just be two PCs a PC dialing into a router or access server at one of the business offices or a PC dialing into a router or access server at an ISP As long as both endpoints have a compatible modem the two can communicate By the time DSL came around in the mid to late 1990s the main goal for remote access was not the capability to connect to any site anywhere but to connect to either the Internet or a corporate IP network In years past modems were used to dial a large variety of different computers which was useful Today you can think of the Internet like you think of the electric company the gas company and so on it s a utility that provides IP connectivity to the rest of the world Because most people today just want access to the utility in other words the Internet DSL can be defined a little differently In fact DSL was designed to provide high speed access between a home or business and the local CO By removing the requirement to allow connection between any two endpoints DSL can be defined to reach much higher speeds Because DSL really just defines how to transmit data between a customer site and the local CO the expectation with DSL is that the data would not flow through DSO channels inside the PSTN Instead it would be forwarded through some IP network By
43. m Routers send periodic full updates and expect to receive periodic updates from neighboring routers m Failure to receive updates from a neighbor in a timely manner results in the removal of the routes previously learned from that neighbor A router assumes that for a route advertised by Router X the next hop router in that route is Router X Routing Protocol Overview 413 Routing Information Protocol Version 1 RIP Version 1 RIP 1 has been around for a long time longer than 15 years for use with IP networks It has many shortcomings compared to some of the relatively newer IP routing protocols but it does work and is an easy tool to use for comparison with the other routing protocols RIP uses hop count for a metric That means that from an individual router s perspective if there are two routers between itself and a subnet its metric for that subnet is 2 Figure 14 3 outlines the concept Figure 14 3 RIP s Use of Hop Count as Metric Excerpt from Routing Table z7 i r F Subnet Metric A 162 11 7 0 1 162 11 8 0 0 162 11 9 0 162 11 8 0 Excerpt from Excerpt from Routing Table Routing Table S0 Subnet Metric t gt Subnet Metric 162 11 7 0 2 7 F a 162 11 7 0 0 162 11 8 0 1 C B 162 11 8 0 0 eS el 162 11 10 0 162 11 7 0 Only a part of the routing table for each router is shown in the figure but from those shown you can see what is meant by
44. network with 100 accuracy Some situations are difficult to simulate For instance it is very challenging to simulate the output of debug commands because the simulator is not actually running IOS If you intend to use NetSim please download the latest list of hints tips and caveats from www ciscopress com 1587200945 GLOSSARY 1OBASE T The 10 Mbps baseband Ethernet specification using two pairs of twisted pair cabling Categories 3 4 or 5 One pair transmits data and the other receives data 10BASE T which is part of the IEEE 802 3 specification has a distance limit of approximately 100 m 328 feet per segment 802 1Q The IEEE standardized protocol for VLAN trunking AAA Authentication Authorization and Accounting Authentication confirms the identity of the user or device Authorization determines what the user or device is allowed to do Accounting records information about access attempts including inappropriate request accounting In security the recording of access attempts See AAA ADSL Asymmetric digital subscriber line One of many DSL technologies ADSL is designed to deliver more bandwidth downstream from the central office to the customer site than upstream AppleTalk DDP The AppleTalk Data Delivery Protocol DDP is the AppleTalk equivalent of the IP protocol It defines a 24 bit address with 16 bits defining the network and 8 bits defining the node ARP Address Resolution Protocol An Internet proto
45. not received Frame 4 or Frame 4 might not have passed the FCS check Name three connection oriented protocols Answer TCP SPX LLC Type 2 and X 25 are some examples of connection oriented protocols that provide error recovery ATM and Frame Relay are also connection oriented but without error recovery Describe how TCP performs error recovery What role do the routers play Answer TCP numbers the first byte in each segment with a sequence number The receiving host uses the Acknowledgment field in segments that it sends back to acknowledge receipt of the data If the receiver sends an acknowledgment number that is a smaller number than the sender expected the sender believes that the intervening bytes were lost so the sender resends them The router plays no role unless the TCP connection ends in the router for example a Telnet into a router A full explanation is provided in the section Error Recovery Reliability How many TCP segments are exchanged to establish a TCP connection How many are required to terminate a TCP connection Answer A three way connection establishment sequence is used and a four way connection termination sequence is used Describe the purpose of the Port Number field in a TCP header Give one example Answer The port numbers are used to help computers multiplex received data For instance a PC with two web browsers open can receive an IP packet The destination TCP port number identifies which
46. number A number that uses dotted decimal notation like IP addresses but the number itself represents all hosts in a single Class A B or C IP network NVRAM Nonvolatile RAM A type of random access memory RAM that retains its contents when a unit is powered off OSI Open System Interconnection reference model A network architectural model developed by the ISO The model consists of seven layers each of which specifies particular network functions such as addressing flow control error control encapsulation and reliable message transfer The OSI reference model is used universally as a method for teaching and understanding network functionality packet A logical grouping of information that includes the network layer header and encapsulated data 586 PAP PAP Password Authentication Protocol An authentication protocol that allows Point to Point Protocol PPP peers to authenticate one another Unlike the Challenge Handshake Authentication Protocol CHAP PAP passes the password and the host name or username in the clear unencrypted partial mesh A network in which devices are organized in a mesh topology with some network nodes organized in a full mesh but others that are connected only to one or two other nodes in the network A partial mesh does not provide the level of redundancy of a full mesh topology but is less expensive to implement Partial mesh topologies generally are used in the peripheral networks that connect to a
47. of Layer 4 Answer Layer 4 the transport layer provides end to end error recovery if requested What is the main purpose s of Layer 3 Answer Layer 3 the network layer defines logical addressing and routing as a means of delivering data across an entire network IP and IPX are two examples of Layer 3 equivalent protocols What is the main purpose s of Layer 2 Answer The data link layer defines addressing specific to a particular medium as part of the means of providing delivery of data across that medium It also includes the protocols used to determine what device s accesses the media at any point in time What is the main purpose s of Layer 1 Answer Layer 1 physical layer is responsible for encoding energy signals onto the medium and interpreting a received energy signal Layer 1 also defines the connector and cabling details Describe the process of data encapsulation as data is processed from creation until it exits a physical interface to a network Use the OSI model as an example Answer Data encapsulation represents the process of a layer adding a header and possibly a trailer to the data as it is processed by progressively lower layers in the protocol specification In the context of OSI each layer could add a header so that other than the true application data there would be six other headers Layers 2 to 7 and a trailer for Layer 2 with this L2PDU being encoded by the physical layer onto the networ
48. of one digit binary numbers The result is another one digit binary number 1 AND 1 yields 1 all other combinations yield a 0 BRI Basic Rate Interface An ISDN interface composed of two bearer B channels and one data D channel for circuit switched communication of voice video and data broadcast address An IP address in each subnet is considered to be the broadcast address for that subnet It is the highest numerical value in the range of numbers for the subnet the broadcast address cannot be assigned as an IP address to a computer Packets sent to this address are delivered to all hosts in the subnet broadcast domain A set of all devices that receive broadcast frames originating from any device within the set Devices in the same VLAN are in the same broadcast domain broadcast subnet When subnetting a Class A B or C network two subnet numbers are discouraged from use one of those two subnets is the broadcast subnet It is the subnet number for which the subnet bits all have a value of binary 1 bus A common physical signal path composed of wires or other media across which signals can be sent from one part of a computer to another Also called a highway CDP Cisco Discovery Protocol A media and protocol independent device discovery protocol that runs on all Cisco manufactured equipment including routers access servers bridges and switches Using CDP a device can advertise its existence to other devices and receive in
49. of the following fields can be used by Ethernet as a type field to define the type of data held in the data portion of the Ethernet frame Answer C and D Which of the following are true about the CSMA CD algorithm Answer B Which of the following would be a collision domain Answer A Which terms describe Ethernet addresses that can be used to communicate with more than one device at a time Answer C and D With autonegotiation on a 10 100 card what characteristics are negotiated if the device on the other end does not perform negotiation at all Answer C What is the main purpose s of Layer 2 Answer The data link layer defines addressing specific to a particular medium as part of the means of providing delivery of data across that medium It also includes the protocols used to determine what device s accesses the media at any point in time 504 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 2 What is the main purpose s of Layer 1 Answer Layer 1 the physical layer is responsible for encoding energy signals onto the medium and interpreting a received energy signal Layer 1 also defines the connector and cabling details 3 What does MAC stand for Answer MAC stands for Media Access Control 4 Name three terms popularly used as a synonym for MAC address Answer NIC address card address LAN address hardware address Ethernet address Token Ring addres
50. of the two browsers should receive the data 518 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 9 List the components of a TCP socket Answer A socket consists of three things an IP address a transport layer protocol TCP or UDP and the TCP or UDP port number 10 How many TCP segments must be sent to establish a TCP connection How many are used with normal TCP connection termination Answer Three TCP segments are needed to establish the connection and four are needed to tear it down under normal operation 11 How many UDP segments must be sent to establish a UDP connection How many are used with normal UDP connection termination Answer UDP does not establish connections because it is not connection oriented Chapter 7 Do Know This Already Quiz 1 In which of the following modes of the CLI could you configure a description of Ethernet0 Answer E The description command is an interface subcommand 2 In which of the following modes of the CLI could you issue a command to reboot the router Answer B The reload command is an exec command so it cannot be issued from any configuration mode User mode does not allow the use of the reload command 3 What type of router memory is used to store the configuration used by the router when it is up and working Answer A The IOS loads the config from NVRAM into RAM during the boot sequence therefore the router use
51. or a switch m Platform The model and OS level running in the device CDP is enabled in the configuration by default The no cdp run global command disables CDP for the entire device and the cdp run global command re enables CDP Likewise the no cdp enable interface subcommand disables CDP just on that interface and the cdp enable command switches back to the default state of CDP being enabled A variety of show cdp command options are available Example 13 11 lists the output of the commands with some commentary following Example 13 11 show cdp Command Options Seville show cdp entry Information for specific neighbor entry interface CDP interface status and configuration neighbors CDP neighbor entries traffic CDP statistics i Output modifiers lt cr gt Seville show cdp neighbor Capability Codes R Router T Trans Bridge B Source Route Bridge S Switch H Host I IGMP r Repeater Device ID Local Intrfce Holdtme Capability Platform Port ID fred Ser 1 172 R 2500 Ser 1 Yosemite Ser 0 2 161 R 2500 Ser 0 2 Switch Eth 0 123 SI WS C3550 2Fas 0 4 Seville show cdp entry fred Device ID fred Entry address es IP address 163 5 8 3 Platform cisco 2500 Capabilities Router Interface Seriali Port ID outgoing port Seriali Holdtime 168 sec Version Cisco Internetwork Operating System Software IOS tm 2500 Software C2500 DS L Version 12 2 3 RELEASE SOFTWARE fc1 continues 394 Chapter 13
52. other IP routing protocols This chapter provides overview of routing protocols and the underlying logic used by these protocols Routing Protocol Overview IP routing protocols have one primary goal to fill the IP routing table with the current best routes it can find The goal is simple but the process and options can be complicated Terminology can get in the way when you re learning about routing protocols This book s terminology relating to routing and routing protocols is consistent with the authorized Cisco courses as well as with most Cisco documentation So just to make sure you have the terminology straight before diving into the details a quick review of a few related terms might be helpful m A routing protocol fills the routing table with routing information Examples include RIP and IGRP m A routed protocol is a protocol with OSI Layer 3 characteristics that define logical addressing and routing The packets defined by the network layer Layer 3 portion of these protocols can be routed Examples of routed protocols include IP and IPX m The term routing type has been used in other Cisco courses so you should also know this term It refers to the type of routing protocol such as link state or distance vector IP routing protocols fill the IP routing table with valid hopefully loop free routes Although the primary goal is to build a routing table each routing protocol has a very important secondary goal of pr
53. proctor will start the software for you all you have to do is follow the instructions You will not be forced to start the exam the instant that you sit down because you will typically be allowed to take a four to five question practice test The practice exam asks you questions in different formats about a totally unrelated topic just to let you get used to the interface Cisco often adds an optional Suggestions for Final Preparation 481 survey before the exam as well just to gather demographic information about who is taking the exam If you ve never taken a Cisco exam take the extra few minutes to take the practice test just to get completely comfortable with the environment m You can actually write on your scratch paper before the exam begins if you like For instance some people like to write down the list of all the valid subnet masks the corresponding prefixes and possibly even the binary equivalents for the decimal numbers used inside subnet masks I ve heard of some people writing down hard to memorize information that they were cramming for in the lobby of the testing center Personally I do not find it helpful to write down the hard to memorize things right before the exam begins but for some people it does help Many people find it helpful to write down the subnetting information just mentioned m The exam engine does not let you go back and change an earlier answer So read each question thoroughly and read every answer
54. scenarios and labs from this book that can be performed using NetSim Note that some of the scenarios in CD only Appendix B cannot be performed on the simulator mainly because those scenarios do not ask you to implement anything on a network making the simulator unnecessary So Table C 1 lists the scenarios and labs that can be performed using NetSim 574 Appendix C Using the Simulation Software for the Hands on Exercises Table C 1 Scenarios and Labs That Can Be Performed Using NetSim NetSim Lab Scenario or Lab Location Topic Number Scenario 1 Chapter 16 Comprehensive scenario for 1 topics in this book Scenario 3 CD only Appendix B LAN switch basic 2 configuration Scenario 6 CD only Appendix B Subnet design with a ClassB 3 network Lab 1 CD only Appendix C Router command line 4 interface familiarization Lab 2 CD only Appendix C 2950 series switch command 5 line interface familiarization Lab 3 CD only Appendix C Basic router IP configuration 6 and management navigation Labs with an asterisk can be performed with the limited function version of NetSim included with this book To perform the other lab scenarios you will need to purchase the full version of NetSim How You Should Proceed with NetSim You can bring up NetSim and dive right in However here a a few suggestions before you are ready to do all the labs Bring up NetSim now and make sure you can at least get to a rout
55. server to a client Asymmetric speeds allow the speed in one direction to be faster than it could be with symmetric speeds accommodating the need for more bandwidth in one direction 6 Compare the V 90 and V 92 modem specifications Answer Based on this chapter V 92 is an improvement over the V 90 standard V 92 supports symmetric and asymmetric speeds whereas V 90 supports only asymmetric speeds The upstream speed has been increased from 33 kbps up to 48 kbps It supports modem on hold which allows the user to accept a voice call in response to a call waiting signal putting the modem connection on hold It also senses the correct operational speed more quickly than V 90 10 11 Chapter 15 561 Compare analog modems ISDN BRIs DSL and cable modems in terms of concurrent support for voice and data Answer Analog modems do not support concurrent voice and data transmission ISDN and DSL both support simultaneous voice and data over the same local loop local phone line Cable allows simultaneous data voice and TV reception Compare analog modems ISDN BRIs DSL and cable modems in terms of whether the data service is always on Answer Analog modems and ISDN BRIs must signal to set up a circuit so any data capabilities such as Internet connectivity are not always on DSL and cable do not require any signaling to set up a circuit in fact no circuit is needed in the PSTN to support these technologies so the
56. support IP TCP UDP and the rest of the higher layer TCP IP protocols Compare and contrast the cabling used by an analog modem and a DSL router modem when connecting to the local phone company line Identify the purpose of each pin on the connector Compare and contrast the cabling used by an ISDN modem and a cable modem when connecting to the local phone company line or cable drop line Identify the purpose of each pin on the connector List four standards bodies that have been involved in the development of DSL standards PART VI Final Preparation Chapter 16 Final Preparation Cuapter Final Preparation So you have made it through most of the book and you have probably either scheduled your INTRO exam or CCNA exam or at least thought about when you want to try to take it Congratulations for getting this far You will soon have finished your first step toward building your networking career r sum This chapter provides some tips on your final preparation for the exam It also provides an example scenario which helps you to pull many of the hands on skills together into a single review section Suggestions for Final Preparation Everyone has their own study habits and you should know what works well for you However here are a few suggestions you can try in the week or two before you take the exam Reread the Foundation Summary sections of each chapter When reviewing tables and definitions yo
57. tasks outlined in Steps A B and C However if you have limited time you might want to review the problem statements and then review the answers for each of the three parts At least you will get a good review of some of the more important commands that could be on the exam If you are reading this chapter as your final review before taking the exam let me take this opportunity to wish you success Hopefully you will be relaxed and confident for your exam and hopefully this book will have helped you build your knowledge and confidence Scenario Part A Planning This scenario has three parts listed as Parts A B and C Part A begins with some planning guidelines that mainly consist of planning an IP addressing scheme for a network After you complete Part A Part B of the scenario asks you to configure the three routers and one switch to implement the planned design Finally Part C asks you to examine router command output and answer questions about the details of current operation of the network Part C also lists some questions related to the user interface and protocol specifications Scenario Part A Planning 483 Your job is to deploy a new network with three sites as shown in Figure 16 1 The decision to use point to point serial links has already been made and the products have been chosen For Part A of this scenario perform the following tasks 1 Plan the IP addressing and subnets used in this network Class B network 163
58. the CO expects to send and receive analog voice over the physical line to a typical home the local loop m The telco converts the received analog voice to the digital equivalent using a codec m The telco converts the digital voice back to the analog equivalent for transmission over the local loop at the destination m The voice call with PCM in use uses 64 kbps through the digital part of the PSTN Analog Modems 441 Analog Modems Analog modems allow two computers to send and receive a serial stream of bits with no physical changes required on the typical analog local loop between a residence and the telco CO Because the switch in the CO expects to send and receive analog voice signals over the local loop modems simply send an analog signal to the PSTN and expect to receive an analog signal from the PSTN However that analog signal represents some bits that the computer needs to send to another computer instead of voice created by a human speaker Similar in concept to a phone converting sound waves into an analog electrical signal a modem converts a string of binary digits on a computer into a representative analog electrical signal Modems encode a binary 0 or 1 onto the analog signal by varying the frequency amplitude or phase Changing the analog signal is referred to as modulation For instance one of the earliest standards called for a modem to send an analog signal of 2250 Hz for a binary 1 and 2100 Hz for binary 0 A mod
59. to how and when OSPF actually sends routing information A router does not send routing information with OSPF until it discovers other OSPF speaking routers on a common subnet The following list gives you some idea of the process 1 Each router discovers its neighbors on each interface The list of neighbors is kept in a neighbor table 2 Each router uses a reliable protocol to exchange topology information with its neighbors 3 Each router places the learned topology information into its topology database 4 Each router runs the SPF algorithm against its own topology database to calculate the best routes to each subnet in the database 5 Each router places the best route to each subnet into the IP routing table Link state protocols do require more work by the routers but the work is typically worth the effort A router running a link state protocol uses more memory and more processing cycles than do distance vector protocols The topology updates require a large number of bytes to describe the details of every subnet every router and which routers are connected to which subnets However because OSPF does not send full updates on a regular short interval like RIP the overall number of bytes sent for routing information is typically smaller Also OSPF converges much more quickly than do distance vector protocols and fast convergence is one of the most important features of a routing protocol 418 Chapter 14 Introduction to Dy
60. with a proctored computer based exam for Cisco certification Do not be alarmed it s not terribly different than using the exam software on the CD that came with the book However you should go into the exam day with the following in mind m You typically need two forms of ID at least one of which is a picture ID A driver s license a passport and a military ID are all valid m The testing center is probably just an extra room inside the offices of a company that does something else for its primary business Often training companies are also testing centers The proctor usually has other responsibilities besides monitoring the exams The proctor seldom enters the testing room other than to bring in another person who has an exam scheduled So do not worry about someone staring at you and making you nervous However most testing centers do have video cameras for monitoring just because you cannot see them it does not mean that they are not watching m You will need to turn off all electronics that you bring with you phone pager and secret decoder rings I typically just leave them in the car They may ask you to leave your pager or phone at the front desk as well m You cannot bring any of your own paper into the room either The proctor will give you something to write on either paper or a dry erase board and marker In either case you should return these to the proctor when you are done m You will take the exam using a PC The
61. 0 packets sec 5 minute output rate bits sec packets sec 2274 packets input 112381 bytes no buffer Received 1913 broadcasts runts giants throttles input errors CRC frame overrun ignored abort 863 packets output 110146 bytes underruns output errors collisions 2 interface resets output buffer failures output buffers swapped out 6 transitions R2 show ip protocol Routing Protocol is rip Sending updates every 30 seconds next due in 6 seconds Invalid after 180 seconds hold down 180 flushed after 240 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing rip Example Example Scenario Part A Planning 491 16 6 Part C R2 show and debug Output Continued Default version control send version 1 receive any version Interface Send Recv Key chain Serial 1 12 Seriali 1 12 EthernetoO 1 12 Automatic network summarization is in effect Maximum path 4 Routing for Networks 163 1 0 0 Routing Information Sources Gateway Distance Last Update 163 1 13 201 120 00 00 02 163 1 23 202 120 00 00 09 Distance default is 120 16 7 Part C R3 show and debug Output R3 show running config Building configuration Current configuration 888 bytes version 12 2 service timestamps debug uptime service timestamps log uptime no service password encryption hostname R3 e
62. 0 seconds RIP 2 Hop count Slow Yes 30 seconds IGRP Calculated based Slow No 90 seconds on constraining bandwidth and cumulative delay EIGRP Same as IGRP Very fast Yes N A except multiplied by 256 OSPF Cost as derived Fast Yes N A from bandwidth by default Integrated IS IS_ Metric Fast Yes N A Table 14 10 outlines some of the key comparison points between RIP and IGRP Table 14 10 RIP and IGRP Feature Comparison Feature RIP Default IGRP Default Update timer 30 seconds 90 seconds Metric Hop count Function of bandwidth and delay the default Can include reliability load and MTU Hold down timer 180 280 Flash triggered updates Yes Yes Mask sent in update No No Infinite metric value 16 4 294 967 295 O amp A 425 O amp A As mentioned in the introduction you have two choices for review questions The questions that follow give you a bigger challenge than the exam itself by using an open ended question format By reviewing now with this more difficult question format you can exercise your memory better and prove your conceptual and factual knowledge of this chapter The answers to these questions are found in Appendix A For more practice with exam like question formats including questions using a router simulator and multiple choice questions use the exam engine on the CD Which interior IP routing protocols covered in this chapter support VLSM Which IP
63. 1 could learn about only Router1 because CDP learns information about only devices that are connected to the same data link 19 What command lists a brief one line description of CDP information about each neighbor Answer The show cdp neighbor command Chapter 14 Do I Know This Already Quiz 1 Which of the following routing protocols are considered to use distance vector logic Answer A and B 2 Which of the following routing protocols are considered to use link state logic Answer E and G 3 Which of the following routing protocols use a metric that is by default at least partially affected by link bandwidth Answer C D and E 4 Which of the following interior routing protocols support VLSM Answer B D E and F 5 Which of the following situations would cause RIP to remove all the routes learned from a particular neighboring router Answer B Distance vector protocols rely on regular receipt of routing updates from their neighbors to continue believing that the routes through that neighbor are still valid 556 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 6 Which of the following interior routing protocols are considered to be capable of converging quickly Answer D E and F 7 Which of the following interior routing protocols use hop count as their metric Answer A and B 8 What update timer is used by IGRP Answer E Q amp A 1 Which interior IP routing
64. 100 146 1001 0010 117 0111 0101 147 1001 0011 118 0111 0110 148 1001 0100 119 0111 0111 149 1001 0101 120 0111 1000 150 1001 0110 121 0111 1001 151 1001 0111 122 0111 1010 152 1001 1000 123 0111 1011 153 1001 1001 124 0111 1100 154 1001 1010 125 0111 1101 155 1001 1011 126 0111 1110 156 1001 1100 127 0111 1111 157 1001 1101 128 1000 0000 158 1001 1110 129 1000 0001 159 1001 1111 130 1000 0010 160 1010 0000 131 1000 0011 161 1010 0001 132 1000 0100 162 1010 0010 133 1000 0101 163 1010 0011 134 1000 0110 164 1010 0100 135 1000 0111 165 1010 0101 continues 567 568 Appendix B Decimal to Binary Conversion Table Decimal Value Binary Value Decimal Value Binary Value 166 1010 0110 196 1100 0100 167 1010 0111 197 1100 0101 168 1010 1000 198 1100 0110 169 1010 1001 199 1100 0111 170 1010 1010 200 1100 1000 171 1010 1011 201 1100 1001 172 1010 1100 202 1100 1010 173 1010 1101 203 1100 1011 174 1010 1110 204 1100 1100 175 1010 1111 205 1100 1101 176 1011 0000 206 1100 1110 177 1011 0001 207 1100 1111 178 1011 0010 208 1101 0000 179 1011 0011 209 1101 0001 180 1011 0100 210 1101 0010 181 1011 0101 211 1101 0011 182 1011 0110 212 1101 0100 183 1011 0111 213 1101 0101 184 1011 1000 214 1101 0110 185 1011 1001 215 1101 0111 186 1011 1010 216 1101 1000 187 1011 1011 217 1101 1001 188 1011 1100 218 1101 1010 189 1011 1101 2
65. 19 1101 1011 190 1011 1110 220 1101 1100 191 1011 1111 221 1101 1101 192 1100 0000 222 1101 1110 193 1100 0001 223 1101 1111 194 1100 0010 224 1110 0000 195 1100 0011 225 1110 0001 Decimal to Binary Conversion Table Decimal Value Binary Value Decimal Value Binary Value 226 1110 0010 227 1110 0011 228 1110 0100 229 1110 0101 230 1110 0110 231 1110 0111 232 1110 1000 233 1110 1001 234 1110 1010 235 1110 1011 236 1110 1100 237 1110 1101 238 1110 1110 239 1110 1111 240 1111 0000 241 1111 0001 242 1111 0010 243 1111 0011 244 1111 0100 245 1111 0101 246 1111 0110 247 1111 0111 248 1111 1000 249 1111 1001 250 1111 1010 251 1111 1011 252 1111 1100 253 1111 1101 254 1111 1110 255 1111 1111 569 APPENDIX Using the Simulation Software for the Hands on Exercises One of the most important skills required for passing the INTRO ICND and CCNA exams is the ability to configure Cisco routers and switches with confidence In fact one of the reasons that this book is relatively long is the effort put into explaining the commands the output of show commands and how the commands work together Many CCNA candidates simply do not get a lot of hands on experience so this book is designed to help those who do not have real gear Another way to practice and develop hands on skills is to use a simulator A c
66. 255 255 255 The last octet is interesting the magic number is 256 240 16 Subnet zero 220 8 7 Copy the network number it s the zero subnet First subnet 220 8 7 Add magic to the last subnet number s interesting octet Next subnet 220 8 Add magic to the previous one Last subnet 220 8 You eventually get her Broadcast subnet 220 8 and then here the broadcast subnet because the next one is 256 which is invalid How many IP addresses could be assigned in each subnet of 134 141 0 0 assuming that a mask of 255 255 255 0 is used If the same static mask is used for all subnets how many subnets are there Answer There will be 25 stbits or 28 number of subnets will be hosts per subnet minus two special cases The 2subnetbits or 28 minus two special cases Number of Number of Network and __ Network Number of Number of Hosts per Number of Mask Bits Host Bits Subnet Bits Subnet Subnets 134 141 0 0 16 8 8 254 254 255 255 255 0 548 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 18 How many IP addresses could be assigned in each subnet of 220 8 7 0 assuming that a mask of 255 255 255 240 is used If the same static mask is used for all subnets how many subnets are there 2hostbits or 24 hosts per subnet minus two special cases The Or 74 minus two special cases Answer There will be number of subnets will be 25u gt n
67. 26 inclusive What values can a Class B network have in the first octet Answer 128 through 191 inclusive 514 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 22 What values can a Class C network have in the first octet Answer 192 through 223 inclusive 23 When subnetting a Class B network do you create the subnet field by taking bits from the network part of the address or the host part Answer Host part 24 When subnetting a Class B network using the entire third octet for the subnet part describe the number of possible subnets created Answer The subnet part consists of a full octet which is 8 bits long You can number 28 things with 8 bits or 256 However 2 subnet numbers are reserved leaving 254 subnets 25 When subnetting a Class A network using the entire second octet for the subnet part describe the number of hosts in each subnet Answer The host part consists of two entire octets in this case which is 16 bits long You can number 216 things with 16 bits or 65 536 However 2 subnet numbers are reserved leaving 65 534 hosts per subnet 26 When a router hears about multiple routes to the same subnet how does it choose which route to use Answer Routing protocols use a metric to describe how good each route is The lower the metric is the better the route is 27 What is the primary purpose of a routing protocol Answer Routing protocols discover the ro
68. 41 7 11 1000 0110 1000 1101 0000 0111 0000 1011 Mask 255 255 255 0 1111 1111 1111 1111 1111 1111 0000 0000 Result 134 141 7 0 1000 0110 1000 1101 0000 0111 0000 0000 Broadcastaddress 134 141 7 255 1000 0110 1000 1101 0000 0111 1111 1111 Given the IP address 193 193 7 7 and the mask 255 255 255 0 what is the broadcast address Answer The broadcast address is 193 193 7 255 Because this is a Class C address and the mask used is 255 255 255 0 the default no subnetting is in use The binary algorithm is shown in the table that follows Address 193 193 7 7 1100 0001 1100 0001 0000 0111 0000 0111 Mask 255 255 255 0 1111 1111 1111 1111 1111 1111 0000 0000 Result 193 193 7 0 1100 0001 1100 0001 0000 0111 0000 0000 Broadcastaddress 193 193 7 255 1100 0001 1100 0001 0000 0111 1111 1111 Given the IP address 200 1 1 130 and the mask 255 255 255 224 what is the broadcast address Answer The broadcast address is 200 1 1 159 The binary algorithm math is shown in the table that follows The easy decimal algorithm is shown in the answer to an earlier question Address 200 1 1 130 1100 1000 0000 0001 0000 0001 1000 0010 Mask 255 255 255 224 1111 1111 1111 1111 1111 1111 1110 0000 Result 200 1 1 128 1100 1000 0000 0001 0000 0001 1000 0000 Broadcastaddress 200 1 1 159 1100 1000 0000 0001 0000 0001 1001 1111 546 Appendix A Answers to the Do Know This Already Quizzes and O amp
69. 5 MAC Media Access Control The lower of the two sublayers of the data link layer defined by the IEEE Synonymous with IEEE 802 3 for Ethernet LANs MAC address A standardized data link layer address that is required for every device that connects to a LAN Ethernet MAC addresses are 6 bytes long and are controlled by the IEEE Also known as a hardware address a MAC layer address and a physical address metric A unit of measure used by routing protocol algorithms to determine the best pathway for traffic to use to reach a particular destination modem Modulator demodulator A device that converts digital and analog signals for the purpose of communicating over analog telephone lines At the source a modem converts digital signals to a form suitable for transmission over analog communication facilities At the destination the analog signals are returned to their digital form Modems allow data to be transmitted over voice grade telephone lines multimode A type of fiber optic cabling with a larger core than single mode cabling allowing light to enter at multiple angles Such cabling has lower bandwidth than single mode fiber but requires a typically cheaper light source such as an LED name server A server connected to a network that resolves network names into network addresses network A collection of computers printers routers switches and other devices that can communicate with each other over some transmission medium network
70. A good night s rest is better than a night full of cramming for most people 482 Chapter 16 Final Preparation The following list gives a short reminder of the things you might want to keep in mind as you prepare to walk in the door at the testing center m Bring two pens m Bring two IDs one with a picture m Turn off your electronics before going to the exam room m Relax A Final Lab Scenario The current CCNA exams include simulated lab questions The best way to prepare for those is to work with live networks using Cisco routers and switches You should also make sure to do all the questions in the testing engine on the CD as it contains a large number of simulated lab questions You can also use the NetSim network simulator on the CD or rent time via online labs Regardless of how much time and effort you spend with hands on practice the following lab scenario can help you with your final preparation if you simply read through the scenario Throughout the book the portions that covered how to do something on a switch or a router focused on the specific topics covered in that chapter The scenario in this chapter touches on many of the topics in this book that are in some way related to configuration or operation of a router or switch So you can use this scenario as part of your strategy for final preparation for the exam If you have enough time review all the parts of the scenario If you have time try to perform all the
71. Basic Router Configuration and Operation Example 13 11 show cdp Command Options Continued Copyright 1986 2001 by cisco Systems Inc Compiled Wed 18 Jul 1 21 10 by pwade advertisement version 2 Seville show cdp neighbor detail Device ID fred Entry address es IP address 163 5 8 3 Platform cisco 2500 Capabilities Router Interface Seriali Port ID outgoing port Seriali Holdtime 164 sec Version Cisco Internetwork Operating System Software IOS tm 2500 Software C2500 DS L Version 12 2 3 RELEASE SOFTWARE fc1 Copyright 1986 2001 by cisco Systems Inc Compiled Wed 18 Jul 01 21 10 by pwade advertisement version 2 Device ID Yosemite Entry address es IP address 10 1 5 252 Platform cisco 2500 Capabilities Router Interface Serial 2 Port ID outgoing port Serial 2 Holdtime 146 sec Version Cisco Internetwork Operating System Software IOS tm 2500 Software C2500 DS L Version 12 2 3 RELEASE SOFTWARE fc1 Copyright 1986 2001 by cisco Systems Inc Compiled Wed 18 Jul 01 21 10 by pwade advertisement version 2 Device ID Switch Entry address es Platform cisco WS C3550 24 Capabilities Switch IGMP Interface Ethernet Port ID outgoing port FastEthernet0 4 Holdtime 160 sec Version Cisco Internetwork Operating System Software IP Troubleshooting Features 395 Example 13 11 show cdp Command Options Continued IOS tm C3550 Software C3550 15Q3L2 M V
72. D64570 Internet address is 163 1 12 202 25 MTU 1500 bytes BW 1544 Kbit DLY 20000 usec reliability 255 255 txload 1 255 rxload 1 255 Encapsulation HDLC loopback not set Keepalive set 10 sec Last input never output never output hang never Last clearing of show interface counters never Input queue 0 75 0 0 size max drops flushes Total output drops 0 Queueing strategy weighted fair Output queue 0 1000 64 0 size max total threshold drops Conversations 0 0 256 active max active max total Reserved Conversations 0 0 allocated max allocated Available Bandwidth 1158 kilobits sec 5 minute input rate bits sec packets sec 5 minute output rate bits sec 0 packets sec 1242 packets input 98477 bytes no buffer Received 898 broadcasts runts giants throttles input errors CRC frame overrun ignored abort 1249 packets output 91395 bytes underruns output errors collisions 2 interface resets output buffer failures output buffers swapped out 12 carrier transitions DCD up DSR up DTR up RTS up CTS up Serial1 is up line protocol is up Hardware is HD64570 Internet address is 163 1 23 202 25 MTU 1500 bytes BW 1544 Kbit DLY 20000 usec reliability 255 255 txload 1 255 rxload 1 255 Encapsulation PPP loopback not set Keepalive set 10 sec LCP Open continues 490 Chapter 16 Final Preparation Example 16 6 Part C R2 show and debug Output Continued Open IPCP CDPC
73. DSL simply will not be available to some people based on the distance to the local CO or the availability of DSL services from the local telco Also even when the home is close enough to the CO sites farther from the CO might run slower than sites closer to the CO 562 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 12 Define what the acronym DSLAM stands for and explain the concept behind how a DSLAM allows voice and data to flow over the same local loop phone line Answer DSLAM stands for DSL access multiplexer with DSL meaning digital subscriber line The DSLAM is connected to the local loop splitting off the voice frequencies 0 to 4000 Hz for the voice switch in the CO It also interprets the higher frequencies as encoded digital signals receiving the ATM cells sent over that digital signal and forwards those ATM cells to the appropriate router 13 Which of the DSL standards is the most common in the United States today What is the range of upstream and downstream speeds for that type of DSL as well as the maximum distance of the local loop Answer ADSL meaning asynchronous DSL is the most popular The downstream speeds range from 1 5 to 8 Mbps with upstream speeds from 64 to 800 kbps The maximum distance is 18 000 feet approximately 5500 meters 14 What protocols are used by DSL at the data link layer Answer ATM Ethernet and PPP 15 Imagine that Andy and Barney are neighbo
74. E in the context of the physical layer and a point to point serial link Answer At the physical layer DTE refers to the device that looks for clocking from the device on the other end of the cable on a link The DCE supplies that clocking For example the computer is typically the DTE and the modem or CSU DSU is the DCE At the data link layer both X 25 and Frame Relay define a logical DTE and DCE In this case the customer premises equipment CPE such as a router and a CSU DSJU is the logical DTE and the service provider equipment the Frame Relay switch and the CSU DSU is the DCE Which layer or layers of OSI are most closely related to the functions of Frame Relay Why Answer OSI Layers 1 and 2 Frame Relay refers to well known physical layer specifications Frame Relay does define headers for delivery across the Frame Relay cloud making it a Layer 2 protocol Frame Relay does not include any routing or logical addressing specifications so it is not a Layer 3 protocol What is the name of the field that identifies or addresses a Frame Relay virtual circuit Answer The data link connection identifier DLCI is used to identify a VC True or False A leased line between two routers provides a constant amount of bandwidth never more and never less Defend your answer y Answer True A leased line creates the cabling equivalent of having a cable between the two routers with the speed clock rate defined by the te
75. L router s Ethernet IP address as its default gateway The PC even can use DHCP to acquire an IP address with the DSL router providing the DHCP server feature DSL provides the Layer 1 encoding features for high speed transmission over the local loop but it also references ATM as the data link protocol to use over the DSL link Back in Chapter 4 Fundamentals of WANs you read about the basic features of ATM and SONET and how ATM sends and receives ATM cells at Layer 2 with SONET providing the Layer 1 transmission details DSL defines how you can use ATM cells over DSL lines instead of over SONET with the ATM cells being forwarded over the DSL connecting from the home to the DSLAM The ISP s router needs to receive the data traffic not the DSLAM in the local CO So the DSLAM forwards the ATM cells over the link to the ISP router probably using an optical cable and Sonet at Layer 1 The receiving ISP router can reassemble the cells and extract the IP packet DSL Summary DSL provides OSI Layer 1 and Layer 2 services to the home The goal of DSL is to deliver IP packets from the remote user to a router a router owned by an ISP or a router resident inside a corporate network To do so DSL provides a digital Layer 1 service serial bit streams in each direction between the remote site and the local CO On top of that DSL uses a combination of ATM Ethernet and PPP to help deliver IP packets between the home and a router at an I
76. M Your boss also says to plan your subnets so that you can have as many subnets as possible rather than allow for larger subnets later When choosing the actual IP address values and subnet numbers you decide to start with the lowest numerical values Assume that point to point serial links will be attached to this router In the previous question what would be the IP subnet of the link attached to serial 0 If another user wanted to answer the same question but did not have the enable password what command s might provide this router s addresses and subnets What must be done to make the output of the show ip route command list subnet masks in decimal format instead of prefixes In what mode would you use the command What are the differences between the clock rate and bandwidth commands Compare and contrast the commands used to set the enable console and telnet passwords on a router In the output of show ip route when a C shows up in the left side of the output on a line for a particular route what does that mean Define the term prefix notation Give two examples What does ICMP stand for To which OSI layer would you consider this protocol to apply most closely Identify two methods to tell a router to ask for name resolution from two different name servers What keyboard sequence suspends a Telnet session in a Cisco router 11 12 13 14 15 16 17 18 19 Q amp A 401 What two commands
77. O channels are in a DS1 in the United States a 1 b 2 c 8 d 16 e 24 f 28 g 32 Do Know This Already Quiz 431 3 Which of the following best describes the function of demodulation by a modem S p 2 p Encoding an incoming analog signal as a digital signal Decoding an incoming digital signal into an analog signal Encoding a set of binary digits as an analog electrical signal Decoding an incoming analog electrical signal into a set of binary digits Encoding a set of binary digits as a digital electrical signal Decoding an incoming digital electrical signal into a set of binary digits 4 Which of the following modem standards do not support 56 kbps speeds downstream h gt V 22 V 22bis V 42 V 90 V 92 V 32 V 32bis V 34 5 Which of the following terms best describes features of an ISDN PRI in Europe B D 2B D 23B D 24B D 30B D 31B D 32B D 432 Chapter 15 Remote Access Technologies 6 7 8 Imagine that you plug an analog phone into an ISDN modem and call a friend at her house where she uses an analog phone using plain old telephone service POTS At which of the following points in a network will a voice codec be used a b c d e Your friend s telephone The phone switch into which your friend s local line is connected The phone switch into which your ISDN BRI line is connected Your ISDN modem Your telephone What does the letter B stand for i
78. P Last input 00 00 03 output 00 00 03 output hang never Last clearing of show interface counters 00 00 15 Input queue 0 75 0 size max drops flushes Total output drops 0 Queueing strategy weighted fair Output queue 0 1000 64 0 size max total threshold drops Conversations 0 1 256 active max active max total Reserved Conversations 0 allocated max allocated Available Bandwidth 1158 kilobits sec 5 minute input rate bits sec packets sec 5 minute output rate bits sec packets sec 1654 packets input 90385 bytes no buffer Received 1644 broadcasts runts giants throttles input errors CRC frame overrun ignored abort 1674 packets output 96130 bytes underruns output errors collisions 8 interface resets output buffer failures output buffers swapped out 13 carrier transitions DCD up DSR up DTR up RTS up CTS up Ethernet is up line protocol is up Hardware is MCI Ethernet address is 0000 0c89 b170 bia 0000 0c89 b170 Internet address is 163 1 2 202 subnet mask is 255 255 255 128 MTU 1500 bytes BW 10000 Kbit DLY 1000 usec reliability 255 255 txload 1 255 rxload 1 255 Encapsulation ARPA loopback not set keepalive set 10 sec ARP type ARPA ARP Timeout 4 00 00 Last input 00 00 00 output 00 00 04 output hang never Last clearing of show interface counters never Queuing strategy fifo Output queue 0 40 drops input queue 0 75 drops 5 minute input rate bits sec
79. Pi9tal BRI No PCM Needed No Analog Signal DTMF PCM Needed Telco ISDN Tones in TA Switch Digital T1 Line Local Loop Analog 1 DSO Channel Digital PR gt A Signal used l R3 j PCM Needed on Helen s Telco ISDN Internal pp Analog Local Loop Switch ISDN f Card Andy s Raleigh CO Analog Phone Local Loop Analog Helen s Phone The analog phone works just like it normally works You pick it up and punch in some digits generating DTMF tones The ISDN TA can t send the tones so it interprets the tones and generates a signaling message over the D channel After the telco sets up a circuit over one of the B channels the TA begins using its PCM codec to convert the incoming analog voice from Integrated Services Digital Network 453 the phone into PCM digits sending them across the B channel In the Figure 15 11 example the other phone is an analog phone connected to the PSTN at Helen s house So the voice switch connected to Helen s phone line converts the incoming digital signal from the back to analog voice using a PCM codec just like it normally does for a call between two analog phone Finally ISDN supports multiple concurrent data bearer channels For instance you can use your PC to dial two different sites at the same time You can make two calls to the same ISP increasing the speed You also can use one B channel for data and make a voice call using the other B channel ISDN Installation and Cablin
80. RIP 2 Table 14 3 Improvements Made to RIP by RIP V2 Feature Description Transmits subnet mask with This feature allows VLSM by passing the mask along with route each route so that the subnet is defined exactly It allows VLSM making RIP 2 a classless routing protocol Provides authentication Both clear text RFC defined and MDS encryption Cisco added feature can be used to authenticate the source of a routing update Includes a next hop router IP A router can advertise a route but direct any listeners to a address in its routing update different router on that same subnet Uses external route tags RIP can pass information about routes learned from an external source and redistributed into RIP Another router then can pass these external tags to that same routing protocol in a difference part of the network effectively helping that other routing protocol pass information Uses multicast routing Instead of broadcasting updates to 255 255 255 255 like updates RIP 1 the destination IP address is 224 0 0 9 an IP multicast address 224 0 0 9 is reserved specifically for use by RIP 2 This reduces the amount of processing required on non RIP speaking hosts on a common subnet The most important feature comparing the two is that RIP 2 supports VLSM Today when choosing a routing protocol RIP 1 would not be the best choice in fact the RIP 1 RFC has been designated for historic status Both protoco
81. SP DSL brings high speed remote access capabilities to the home Depending on the distance to the local CO and the DSL standard supported by the local telco DSL can support over 1 Mbps It supports concurrent voice and data with the data service always being turned on no dialing is required And the service speed does not degrade when more users are added to the network 460 Chapter 15 Remote Access Technologies DSL has some obvious drawbacks DSL simply will not be available to some people particular those in rural areas based on the distance from the home to the CO The local telco must have DSL equipment in the CO before it or any ISP can offer DSL services Also even when the home is close enough to the CO sites farther from the CO might run slower than sites closer to the CO Cable Modems Of all the access technologies covered in this chapter cable modems are the only one not using a phone line from the local telco for physical connectivity Many homes also have a cable TV service supplied by an analog electrical signal entering the home over a coaxial cable in other words over the cable TV cabling Cable modems provide an always on Internet access service while allowing you to surf the Internet over the cable and make all the phone calls you want over your telephone line and you can watch TV at the same time Cable modems use some of the bandwidth that otherwise might have been allocated for new TV channels using thos
82. V2 IGRP EIGRP OSPF Integrated IS IS 406 Chapter 14 Introduction to Dynamic Routing Protocols 7 Which of the following interior routing protocols use hop count as their metric a b RIP V1 RIP V2 IGRP EIGRP OSPF Integrated IS IS 8 What update timer is used by IGRP a b c d e f 5 seconds 10 seconds 30 seconds 60 seconds 90 seconds None of the above The answers to the Do I Know This Already quiz are found in Appendix A Answers to the Do I Know This Already Quizzes and Q amp A Sections The suggested choices for your next step are as follows 6 or less overall score Read the entire chapter This includes the Foundation Topics and Foundation Summary sections and the Q amp A section 7 or 8 overall score If you want more review on these topics skip to the Foundation Summary section and then go to the Q amp A section Otherwise move to the next chapter Routing Protocol Overview 407 Foundation Topics To pass the INTRO exam you need to know some basic information about several IP routing protocols For the ICND exam you will need to know distance vector concepts as well as how to configure two distance vector IP routing protocols the Routing Information Protocol RIP and the Interior Gateway Routing Protocol IGRP You will also need to know the concepts behind Enhanced IGRP EIGRP as well as Open Shortest Path First OSPF two
83. Which wires are used by a typical Ethernet CATS cable Which ones are used for transmit and which ones are used to receive by an Ethernet card Answer Ethernet cards transmit on the pair using pins 1 and 2 and receive on the pair at pins 3 and 6 Which TIA standards for UTP cabling support 10BASE T Answer CAT3 5 5e and 6 What are the maximum lengths for coaxial cables as used by 1OBASES 10BASE2 Answer 500 m and 185 m respectively What are key differences between multimode and single mode optical cabling Answer Multimode cabling typically supports shorter distances than single mode Single mode uses a much smaller diameter for the glass fiber which allows for the greater distances What types of cabling are least susceptible to having someone eavesdrop and somehow discover what is being transmitted over the cable Answer Optical cables do not emit any EM radiation outside the cable as do metallic copper cables So you cannot simply sense what signal is crossing over an optical cable without physically breaking into the cable which makes the cable unusable What are the IEEE standards for 10BASE T Fast Ethernet Gigabit Ethernet and 10 Gigabit Ethernet Answer 802 3 802 3u Fast Ethernet 802 3z and 802 3ab Gigabit Ethernet and 802 3ae 10 Gigabit 540 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 12 Which variations on the Fast Ethernet standard which use nam
84. a Cable Network Systems MCNS MAC You might remember that MAC stands for Media Access Control MCNS is similar to Ethernet s MAC as defined in the IEEE 802 3 specification including the use of Ethernet MAC addresses So although all downstream data is sent to all drops in the cable system only those with a cable modem know that data has been received and only the PCs with the correct MAC address process the data MCNS also defines the physical encoding details MCNS calls for the use of a modulation method called quadrature amplitude modulation QAM Two options can be used for downstream data one called QAM 64 and the other called QAM 256 QAM 64 represents 6 bits per baud and QAM 256 represents 8 bits per baud Table 15 6 summarizes some of the key reference information about downstream data over cable Table 15 6 Downstream Data over Cable Interesting Facts Downstream Rate OSI Layer 1 QAM 64 and QAM 256 encoding OSI Layer 2 MCNS MAC and IFFE 802 2 LLC Multiplexing used Frequency division multiplexing Speed 30 to 40 Mbps Upstream Data The upstream data channel uses a totally separate frequency range than the downstream channel so no collisions occur between downstream and upstream data However all upstream data from multiple cable subscribers does share the same frequency range the same channel essentially so collisions can occur between data sent toward the Internet by the different home use
85. a Cisco router Answer Ctrl Shift 6 followed by x 554 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 11 What two commands and what part the command output tells you which suspended Telnet connection will be reconnected if you just press the Enter key without any characters typed on the command line Answer show sessions and where Both commands supply the same information The suspended session with an asterisk in the left side of the output line designates the session to which you would be connected if you just pressed Return with no characters on the command line 12 Imagine that you typed a ping command and got 5 sent through the network Be as specific as possible back What type of messages were Answer ICMP echo request messages were sent by the ping command with the remote host replying with five ICMP echo reply messages 13 How do you make a router not ask for DNS resolution from a name server Answer By using the no ip domain lookup global configuration command 14 Imagine that you are just logged in at the console of R1 and you Telnet to routers R2 R3 and R4 in succession but you suspended your Telnet connection each time in other words all three Telnet connections go from R1 to the other three routers respectively What options do you have for reconnecting to R2 Answer You can use the resume 1 command or just use the 1 command 15 Imagine that you ar
86. a circuit over an analog local line Instead of DTMF tones ISDN defines a set of messages that are sent over the D channel to the local CO As a result the PSTN sets up a circuit to the ISDN device whose phone number was put inside the signaling message Figure 15 9 outlines the process and the result Figure 15 9 D Channel Call Setup Signaling and Resulting B Channel Call BRI come N ies l 7 q B1 cal Call Setup 5 y D Fred 57 a ea F lows11957 Barney Call Setup Call Setup Flows Flows o OE 2 ZJE wey Mesa Fred The service provider can use anything it wants to set up the call inside its network ITU Q 931 messages are used for signaling between the ISDN device and the CO typically Signaling System 7 SS7 is used between the two telco switches the same protocol used inside phone company networks to set up circuits for phone calls When the call is established a 64 kbps circuit exists between a B channel on each of the two routers in the figure The routers can use High Level Data Link Control HDLC but they typically use PPP as the data link protocol on the B channel from end to end As on leased lines and dialed circuits using modems the switches in the phone company do not interpret the bits sent inside this circuit they just help create a serial bit stream in each direction The D channel remains up all the time so that new signaling messages can be sent and received Because the signals are sent outside the chan
87. a lot of work done to keep the size down still exceed 100 000 routes BGP advertises only routing information to specifically defined peers using TCP By using TCP a router knows that any routing updates will be re sent if they happen to get lost in transit BGP uses a concept called autonomous systems when describing each route An autonomous system AS is a group of devices under the control of a single organization in other words that organization has autonomy from the other interconnected parts of the Internet An AS number ASN is assigned to each AS uniquely identifying each AS in the Internet BGP includes the ASNS in the routing updates to prevent loops Figure 14 1 shows the general idea Figure 14 1 BGP Uses ASNs to Prevent Routing Loops Enterprise A ASN 21 ISP2 ASN 2 ISP1 ASN 1 Network 9 0 0 0 Network 9 0 0 0 AS Path 21 1 2 Network 9 0 0 0 ISP3 ASN 3 AS Path 21 1 2 3 4 ISP4 ASN 4 gt Network 9 0 0 0 AS Path 21 1 2 3 Enterprise B ASN 22 Routing Protocol Overview 411 Notice that in the figure the BGP updates sent to each successive AS show the ASNs in the route When R1 receives the BGP update from R4 it notices that its own ASN in found inside the AS path and ignores that particular route BGP does not use a metric like internal routing protocols Because BGP expects to be used between different ISPs and between ISPs and
88. a routing protocol the correct routes would have been known and the second ping would have worked The ping command itself supplies many creative ways to use echo requests and replies For instance the ping command enables you to specify the length as well as the source and destination addresses and it also enables you to set other fields in the IP header IP Troubleshooting Features 385 Destination Unreachable ICMP Message The ICMP Destination Unreachable message is sent when a message cannot be delivered completely to the application at the destination host Because packet delivery can fail for many reasons there are five separate unreachable functions codes using this single ICMP unreachable message All five code types pertain directly to an IP TCP or UDP feature The network shown in Figure 13 3 helps you understand them Figure 13 3 Sample Network for Discussing ICMP Unreachable Codes 10 1 1 0 24 S Fred Er 10 1 3 0 24 Er 10 1 2 0 24 10 1 2 14 Assume that Fred is trying to connect to the web server called Web Web uses HTTP which in turn uses TCP as the transport layer protocol Three of the ICMP unreachable codes can possibly be used by Routers A and B The other two codes are used by the web server These ICMP codes are sent to Fred as a result of the packet originally sent by Fred Table 13 5 summarizes the more common ICMP unreachable codes After the table the text explains how each ICMP code might be
89. abled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Security level is default Split horizon is disabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is enabled IP fast switching on the same interface is enabled IP Flow switching is disabled IP Feature Fast switching turbo vector IP multicast fast switching is disabled IP multicast distributed fast switching is disabled IP route cache flags are Fast Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP IP header compression is disabled RTP IP header compression is disabled Probe proxy name replies are disabled Policy routing is disabled Network address translation is disabled WCCP Redirect outbound is disabled WCCP Redirect inbound is disabled WCCP Redirect exclude is disabled BGP Policy Mapping is disabled 378 Chapter 13 Basic Router Configuration and Operation First here is a quick introduction to the four commands in the example The show ip route command lists routes to the three subnets connected to the Seville router namely 10 1 130 0 10 1 129 0 and 10 1 3 0 all with mask 255 255 255 0 prefix 24 The output from the command lists a C in the first column which according to the notes at the beginning of the command output means connected In other words this router is connected directly to
90. ables that stretch from a house to the CO Some DSL variants allow the local loop to be much longer while others allow for only a shorter local loop For the standards with a shorter local loop the transmission rates tend to be much higher a simple design trade off ADSL and SDSL tend to be the most popular option in the United States today Digital Subscriber Line Another architectural difference among the different specifications is that some DSL variants use asymmetric transmission rates while others use symmetric rates Table 15 5 lists the major DSL variants the standard defining that variant the speeds the distance limitations and encoding Table 15 5 DSL Technologies Standards Comparison Modulation Encoding Distance DSL Type Standards Technique Speed Limit Full rate ADSL ANSI T1 413 Discrete multitone DMT Downstream speed of 384 to 18 000 feet G DMT Issue 2 or carrierless amplitude 8 Mbps upstream speed phase CAP slower up to 1 024 Mbps G Lite ITU T G 992 1 DMT Downstream speed up to 18 000 feet ITU T G 992 2 1 544 Mbps to 6 Mbps upstream speed up to 640 kbps Very high data ETSI and ANSI DMT single carrier 12 96 Mbps to 52 8 Mbps 4500 feet amplitude modulation TC PAM both upstream and downstream speed rate DSL VDSL in process modulation SCM for both upstream and downstream speed ISDN DSL ANSI ETR 080 Two binary one quaternary 144 kbps for both upst
91. access and other factors allowing access through the Internet might be cheaper than providing the capability for users to connect directly into the corporate network This chapter begins by covering some background information about the Public Switched Telephone Network PSTN Most remote access technologies use the PSTN for basic physical access The chapter continues with coverage of each of the four types of remote access technologies modems ISDN DSL and cable Perspectives on the PSTN The Public Switched Telephone Network PSTN was built to support traffic between telephones in other words voice traffic Three of the four access technologies covered in this chapter happen to use the PSTN so a basic understanding of the PSTN can help you appreciate how modems ISDN and DSL work If you already know a fair amount about the PSTN feel free to jump ahead to the section titled Analog Modems Sound waves travel through the air by vibrating the air The human ear hears the sound because the ear vibrates as a result of the air inside the ear moving which in turn causes the brain to process the sounds that were heard by the ear The PSTN however cannot forward sound waves Instead a telephone includes a microphone which simply converts the sound waves into an analog electrical signal The PSTN can send the electrical signal between one phone and another On the receiving side the phone converts the electrical signal back to
92. addresses that you chose for your answer are fine I just picked numbers between 200 and 209 for the last octet for router addresses and between 210 and 239 for the switches and PCs For the servers I made the last octet match the server number In real networks you might reserve particular ranges of last octet values in each subnet for network overhead devices For instance all of your routers LAN interface IP addresses might always be between 1 and 5 Scenario Part B Configuration The next step in your job is to deploy the network designed in Part A Perform the following tasks 1 Configure IP addresses based on the design from Part A 2 Although this book did not cover RIP configuration assume that someone else who knows how to configure RIP will configure the routers to support RIP 3 Use PPP as the data link protocol on the link between R2 and R3 Use the default serial encapsulation elsewhere 4 Configure basic administrative settings for SW3 assuming that it is a 2950 series switch Set the host name IP address default gateway enable password telnet password and console password Save the configuration as well Solutions to Part B Configuration Examples 16 1 16 2 16 3 and 16 4 show the configurations for Part B Example 16 1 R1 Configuration hostname R1 l interface Seriald Example Example Example 16 1 R1 Configuration Continued ip address 163 1 12 201 255 255 255 128 l interface Se
93. alled an f connector When using a cable modem the CATV company becomes your ISP Everything between your house and the router at the head end is a single physical and data link The PC in your home uses a router owned by the cable company housed at the head end site as its default gateway In fact the PC typically uses DHCP to discover its IP address and the IP address of its default gateway the DHCP server would be inside the cable company s IP network typically at the head end site Conceptually what happens between the home and the cable head end is similar to a single LAN segment The details of course are different but the cable installation provides a combination of Layer 1 and Layer 2 protocols to let a PC deliver IP packets to a router inside the cable network So as you read about the details of what happens between the home and the router at the head end keep in mind that the goal is simply to deliver IP packets between the home and the head end router and vice versa 1 and Layer 2 between the Home and the Head End Cable TV systems originally were built to send TV video and audio signals to lots of places with no need to receive a signal back In other words the idea of having someone s TV send some information back to the cable company was not even under consideration Because the original CATV architecture allowed for sending signals from the head end outward and the capability for two way communication was added later
94. am The ip address interface subcommand assigns an IP address and mask to an interface If the associated interface is also in an up and up status the router adds a connected route to the routing table for the subnet connected to that interface Example 13 12 shows an example configuration with the resulting connected routes Example 13 12 Albuquerque Router Configuration and Connected Routes Albuquerque configure terminal Enter configuration commands one per line End with CNTL Z Albuquerque config interface serial 0 Albuquerque config if ip address 10 1 128 251 255 255 255 0 Albuquerque config interface serial 1 Albuquerque config if ip address 10 1 130 251 255 255 255 0 Albuquerque config interface ethernet 0 Albuquerque config if ip address 10 1 1 251 255 255 255 0 Albuquerque show ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 E1 OSPF external type 1 E2 OSPF external type 2 E EGP i IS IS L1 IS IS level 1 L2 IS IS level 2 ia IS IS inter area candidate default U per user static route o ODR P periodic downloaded static route Gateway of last resort is not set 10 0 0 0 24 is subnetted 3 subnets Cc 10 1 1 is directly connected Ethernet 0 10 1 130 0 is directly connected Seriali C 10 1 128 0 is directly connected Seriald
95. amples as the highest frequency you need 8000 samples To make sure the voice sounded good after being decoded they decided to use 256 different binary values each representing a different combination of amplitude frequency and phase To represent the 256 values they needed 8 bits for 8000 samples per second 64 kbps is needed for a PCM encoded voice call Because a single call needs 64 kbps the digital PSTN first was built on a basic transmission speed of 64 kbps A single 64 kbps channel was dubbed a Digital Signal Level 0 or DSO In the United States the phone company American Telephone and Telegraph AT amp T by that point in its history decided to create hardware that could multiplex 24 DSOs onto a single line so it called that type of line a Digital Signal Level 1 or DS1 The more popular name for a DS1 today of course is T1 Some parts of the world followed AT amp T s lead for DS1 with 24 DSO channels and other parts of the world mainly Europe and Australia chose instead to combine 32 different 64 kbps DSO channels onto a single line which is the basis for today s Els As you might imagine even faster digital facilities are defined as well such as a T3 line which has 28 T1s in it Finally this small history lesson comes to an end Most of the work on modems and ISDN and some of the work for DSL occurred with the expectation that these technologies needed to work over the PSTN In summary m The telco switch in
96. and what part the command output tells you which suspended Telnet connection will be reconnected if you just press the Enter key without any characters typed on the command line cy Imagine that you typed a ping command and got 5 back What type of messages were sent through the network Be as specific as possible How do you make a router not ask for DNS resolution from a name server Imagine that you are just logged in at the console of R1 and you Telnet to routers R2 R3 and R4 in succession but you suspended your Telnet connection each time in other words all three Telnet connections go from R1 to the other three routers respectively What options do you have for reconnecting to R2 Imagine that you are just logged in at the console of R1 and you Telnet to routers R2 R3 and R4 in succession but you suspended your Telnet connection each time in other words all three Telnet connections go from R1 to the other three routers respectively What options do you have for reconnecting to R4 List the five key pieces of information that can be gathered using CDP as mentioned in the chapter Imagine a network with Switch1 connected to Router1 with a point to point serial link to Router2 which in turn is connected to Switch2 Assuming that you are logged into R1 what commands could be used to find the IP addresses of Router2 and Switch1 without logging in to either device Imagine that a network with Switch1 is
97. ardware is HD64570 Internet address is 10 1 130 253 24 MTU 1500 bytes BW 1544 Kbit DLY 20000 usec reliability 255 255 txload 1 255 rxload 1 255 Encapsulation HDLC loopback not set Keepalive set 10 sec Last input never output never output hang never Last clearing of show interface counters never Input queue 0 75 0 0 size max drops flushes Total output drops 0 Queueing strategy weighted fair Output queue 0 1000 64 0 size max total threshold drops Conversations 0 0 256 active max active max total Configuring IP Addresses 377 Example 13 5 Seville Router Routing Table and Interface Status Commands Continued Reserved Conversations 0 allocated max allocated Available Bandwidth 1158 kilobits sec 5 minute input rate bits sec packets sec 5 minute output rate bits sec packets sec packets input bytes no buffer Received broadcasts runts giants throttles input errors CRC frame overrun ignored abort packets output bytes underruns output errors collisions 1 interface resets output buffer failures output buffers swapped out carrier transitions DCD up DSR up DTR up RTS up CTS up Seville show ip interface serial 1 Seriali is up line protocol is up Internet address is 10 1 129 253 24 Broadcast address is 255 255 255 255 Address determined by non volatile memory MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is dis
98. as introduced you to some of the key terms and points of comparison for these routing protocols as well as a few others Table 14 6 summarizes the most important points of comparison between the interior routing protocols and Table 14 7 lists some of the key terminology Table 14 6 Interior IP Routing Protocols Compared Summary Supports VLSM Default Period Routing Convergence and Is a Classless for Full Routing Protocol Metric Speed Routing Protocol Updates RIP 1 Hop count Slow No 30 seconds RIP 2 Hop count Slow Yes 30 seconds IGRP Calculated based on Slow No 90 seconds constraining bandwidth and cumulative delay EIGRP Same as IGRP Very fast Yes N A except multiplied by 256 OSPF Cost as derived Fast Yes N A from bandwidth by default Integrated Metric Fast Yes N A IS IS Routing Protocol Overview 421 Routing Protocol Terminology Term Definition Routing protocol A protocol whose purpose is to learn the available routes place the best routes into the routing table and remove routes when they are no longer valid Exterior routing protocol A routing protocol designed for use between two different organizations These typically are used between ISPs or between a company and an ISP For example a company would run BGP an exterior routing protocol between one of its routers and a router inside an ISP Interior routing protocol A routing protoco
99. at is being forwarded when routers perform routing Answer A What are the two main functions of each OSI Layer 3 equivalent protocol Answer Path selection which is also called routing and logical addressing Assume that PC1 sends data to PC2 and PC2 is separated from PC1 by at least one router Are the IP addresses of the PCs in the same IP subnet Explain your answer Answer They must be in different subnets IP addressing rules require that IP hosts separated by a router be in different subnets Assume that PC1 sends data to PC2 and PC2 is not separated from PC1 by at least one router Are the IP addresses of the PCs in the same IP subnet Explain your answer Answer They must be in the same subnet IP addressing rules require that IP hosts not separated by a router be in the same subnet How many bits are present in an IP address Answer IP addresses have 32 bits a variable number in the network portion and the rest of the 32 in the host portion IP Version 6 uses a 128 bit address How many bits are present in an IPX address Answer IPX addresses have 80 bits 32 bits in the network portion and 48 bits in the node portion How many bits are present in an AppleTalk address Answer AppleTalk addresses have 24 bits 16 in the cable range portion and 8 bits in the node portion 512 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 7 Name the two main parts of an IPX address Which
100. ata communication between computers wasn t a consideration for the original PSTN It just wanted to get these analog electrical signals which represented sounds from one place to the other To set up a circuit when the PSTN first got started you picked up your phone A flashing light at a switchboard at the local phone company office told the operator to pick up the phone and then you told the operator who you wanted to talk to If it was a local call the operator completed the circuit literally by patching the cable at the end of the phone line connected to your house to the end of the phone line connected to the house of the person you were calling Figure 15 2 depicts the basic concept Perspectives onthe PSTN 437 Figure 15 2 Human Operator Setting Up a Circuit at a Switchboard Switchboard Helen Andy Barney Floyd Gomer Barney Floyd Sarah In the figure Sarah the operator picks up the phone when she sees a light flashing telling her that someone at Andy s house has picked up the phone Andy might say something like Sarah I want to talk to Barney Because Andy Sarah and Barney probably all knew each other that was enough Ina larger town Andy might simply say Please ring phone number 555 1212 and Sarah would connect the call In fact patching the call on the switchboard is where we got the old American saying patch me through Over the years the signaling to set up a circuit
101. cation developed by Bellcore and designed to run on optical fiber STS 1 is the basic building block of SONET It was approved as an international standard in 1988 star A method of connecting devices in which endpoints on a network are connected to a common central switch by point to point links storage router A device that sits between an IP network and storage devices translating between disk IO protocols as they pass through non IP and IP networks STP Shielded twisted pair A two pair wiring medium used in a variety of network implementations Shielded twisted pair cabling has a layer of shielded insulation to reduce electromagnetic interference EMI Can also refer to Spanning Tree Protocol which is used to prevent bridging switching loops subnet broadcast address Same thing as broadcast address subnet mask A 32 bit address mask used indicate the bits of an IP address that are being used for the subnet part of the address Sometimes referred to simply as the mask subnet Subnets are subdivisions of a Class A B or C network as configured by a network administrator Subnets allow a single Class A B or C network to be used instead of multiple networks and still allow for a large number of groups of IP addresses as is required for efficient IP routing subnetting The process of subdividing a Class A B or C network and into smaller portions called subnets switch A network device that filters forwards and floods frames bas
102. cause they support far more B channels on a single physical line Imagine an ISP that supports ISDN with 1000 customers If that ISP wanted to support up to 230 concurrent ISDN customers each using a single B channel that ISP 452 Chapter 15 Remote Access Technologies would need 10 PRIs assuming that it was in the United States Also each user might want to use both B channels at the same time doubling the speed to the Internet to support 2 B channels each for 230 concurrent users that ISP would need 460 B channels or the equivalent of 20 PRIs However if it just used BRI lines it would need 230 different physical BRI lines which probably would be much more expensive would require more equipment and would be a cabling hassle ISDN supports voice as well as data circuits ISDN BRI circuits do not support analog voice but they do support digital voice You might recall that a single PCM voice call requires 64 kbps and that a single B channel provides 64 kbps So ISDN devices like a terminal adapter perform the PCM encoding and decoding features and send the voice traffic over a B channel In fact most ISDN modems have two RJ 11 ports that can be used to connect a normal analog phone Figure 15 11 depicts the cabling and some important concepts about how it all works Figure 15 11 ISDN Support for Voice Andy s P PSTN No PCM Needed on Andy s Digital Local Loop RS 232 Cable i Local Loop Mayberry CO TA
103. ciated with routing in large networks interior routing protocol A routing protocol designed for use within a single organization For example an entire company might choose the IGRP routing protocol which is an interior routing protocol IOS Cisco operating system software that provides common functionality scalability and security for all Cisco products Cisco IOS Software allows centralized integrated and automated installation and management of internetworks while ensuring support for a wide variety of protocols media services and platforms IP Internet Protocol The network layer protocol in the TCP IP stack offering a connectionless internetwork service 584 IP address IP address A 32 bit address assigned to hosts using TCP IP Each address consists of a network number an optional subnetwork number and a host number The network and subnetwork numbers together are used for routing and the host number is used to address an individual host within the network or subnetwork IPX Internetwork Packet Exchange A Novell NetWare network layer Layer 3 protocol used for transferring data from servers to workstations IPX is similar to IP and XNS iSCSI IP SCSI A protocol for sending and receiving SCSI commands over an IP network providing file level access to shared storage devices ISDN Integrated Services Digital Network A service offered by telephone companies that permits telephone networks to carry data voice and othe
104. col used to map an IP address to a MAC address Defined in RFC 826 asynchronous The lack of an imposed time ordering on a bit stream Practically both sides agree to the same speed but there is no check or adjustment of the rates if they are slightly different However because only 1 byte per transfer is sent slight differences in clock speed are not an issue A start bit is used to signal the beginning of a byte ATM Asynchronous Transfer Mode The international standard for cell relay in which multiple service types such as voice video or data are conveyed in fixed length 53 byte cells Fixed length cells allow cell processing to occur in hardware thereby reducing 578 ATM transit delays ATM is designed to take advantage of high speed transmission media such as E3 SONET and T3 authentication In security the verification of the identity of a person or a process See AAA authorization In security the determination of a user or devices rights in a network See AAA auxiliary port A physical connector on a router that is designed to be used to allow a remote terminal or PC with a terminal emulator to access a router using an analog modem balanced hybrid A term that refers to a third general type of routing protocol algorithm the other two being distance vector and link state EIGRP is the only routing protocol that Cisco classifies as using a balanced hybrid algorithm Boolean AND A math operation performed to a pair
105. command help if you knew that a show command option begins with a c but you cannot recall the option Answer show c Help would appear immediately after you typed the symbol You would not need to press Enter after the If you did so the switch would try to execute the command with only the parameters that you had typed after the 5 While you are logged in to a switch you issue the command copy and get a response of Unknown command computer name or host Offer an explanation for why this error message appears Answer You were in user mode You must be in enable privileged mode to use the copy command When in user mode the switch does not provide help for privileged commands and it treats the request for help as if there is no such command 6 How can you retrieve a previously used command Name two ways Answer Use Ctrl p and the up arrow literally the up arrow key on the keyboard Not all terminal emulators support Ctrl p or the up arrow so recalling both methods is useful 7 What configuration command causes the switch to require a password from a user at the console What configuration mode context must you be in That is what command s must be typed before this command after entering configuration mode List the commands in the order in which they must be typed while in config mode line console login Answer The line console 0 command is a context setting command it adds no information to the con
106. connected to Router1 with a point to point serial link to Router2 which in turn is connected to Switch2 You can log in only to Switch1 Which of the other devices could Switch1 learn about using CDP Why What command lists a brief one line description of CDP information about each neighbor This chapter covers the following subjects m Routing Protocol Overview Cuapten TA Introduction to Dynamic Routing Protocols The United States Postal Service routes a huge number of letters and packages each day To do so the postal sorting machines run fast sorting lots of letters Then the letters are placed in the correct container and onto the correct truck or plane to reach the final destination However if no one programs the letter sorting machines to know where letters to each ZIP code should be sent the sorter can t do its job Similarly Cisco routers can route many packets but if the router doesn t know any routes it can t do its job This chapter introduces the basic concepts behind IP routing protocols and lists some of the key features of each of the IP routing protocols covered on the INTRO exam Cisco expects CCNAs to demonstrate a comfortable understanding of the logic behind the routing of packets and the different but related logic behind routing protocols the protocols used to discover routes To fully appreciate the nuances of routing protocols you need a thorough understanding of routing the process
107. cted to Therefore the information in link state updates is much more detailed than the equivalent information with distance vector updates The more detailed information allows a link state protocol to build a mathematical representation of the network topology whereas distance vector protocols simply know that subnets exist and where to send packets to reach those subnets What term describes the underlying logic behind the OSPF routing protocol Answer Link state 558 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections Chapter 15 Do Know This Already Quiz 1 Which of the following acronyms identifies a voice codec used to encode analog voice signals into a 64 kbps digital data stream Answer D 2 How many DSO channels are in a DS1 in the United States Answer E 3 Which of the following best describes the function of demodulation by a modem Answer D Modems demodulate an analog signal sent by the phone company The goal is to re create the original bits sent by the other modem so the demodulation function converts the analog signal into the bits that it was intended to represent 4 Which of the following modem standards do not support 56 kbps speeds downstream Answer A B C F G and H 5 Which of the following terms best describes features of an ISDN PRI in Europe Answer E PRIs in Europe are based on E1 circuits which have 32 DSO channels One channel is reserve
108. customers BGP allows for a very robust set of alternatives for deciding what route to use these alternatives are called policies Routing policy can be based on the fact that an ISP might have a better business relationship with a particular ISP For instance in Figure 14 1 packets from Enterprise B toward Enterprise A can take the high route from ASN 3 to ASN 2 and then to ASN 1 if ISP3 has a better business relationship with ISP2 as compared with ISP4 In the next section you will learn about interior routing protocols and how they use some more obvious metrics Distance Vector Protocols RIP and IGRP Distance vector protocols advertise routing information by sending messages called routing updates out the interfaces on a router These updates contain a series of entries with each entry representing a subnet and a metric The metric represents how good the route is from that router s perspective with a smaller number being a better route Any routers that receive a copy of a distance vector routing update receive that information and possibly add some routes to their routing table The receiving router adds the routes only if the routing update described a route to a subnet that it did not already know about or if it described a route that already was known but the newly learned route has a better lower metric Figure 14 2 depicts the basic process Figure 14 2 Basic Distance Vector Routing Update with Resulting Learned
109. d dual tone multifrequency DTMF tones just like it would for a voice call When the circuit has been established by the telco the two modems must agree to what modem standard they will use As long as the two modems use the same rules for how they perform modulation and demodulation the modems can communicate Many modem standards exist and many modems support several standards Modems can probe and negotiate to find the best modem standard that both endpoint modems support These standards are explained briefly and listed later in the chapter Note that the PSTN still converts the analog signals to and from PCM using a codec In effect the data ping pongs between different states as it passes through the network 1 The bits start out stored in digital form on a computer 2 The bits are converted to an analog signal by the modem 3 The analog signal is converted into a different digital format by a switch in the PSTN using a PCM codec 4 The CO switch near the receiving end using a PCM codec to convert back to an analog signal 5 The receiving modem converts the incoming analog signal to the correct set of bits Modems work well and have been around for a long time so the conversion steps do not pose a problem Modulation and Demodulation Most people can fully appreciate the concept of the speed of a dialed circuit in terms of bits per second However another term baud often is used to describe the speed of a modem In
110. d for framing and one channel is used for a D channel leaving 30 B channels 6 Imagine that you plug an analog phone into an ISDN modem and call a friend at her house where she uses an analog phone using plain old telephone service POTS At which of the following points in a network will a voice codec be used Answer B and D Because the ISDN modem sends only digital signals over the local loop it must convert the analog voice from the phone connected to it into digital voice using a voice codec 7 What does the letter B stand for in the ISDN term B channel Answer A 8 Which of the following DSL standards has a limit of 18 000 feet for the length of the local loop Answer C Q amp A 10 11 12 13 14 15 Chapter 15 559 Imagine a local phone line from a house to a local telco CO When the customer at that house requests DSL service what type of device does the telco move the CO end of the local line to Answer A The CO uses a DSLAM to terminate local loops that use DSL A DSL router or DSL modem is connected to the local loop at the subscriber home location Which of the following protocols are used by DSL modem and routers for data link layer functions Answer A B and C DSL calls for the use of PPP over ATM PPPoA over the DSL part of the network PPP can extend to the PCs at the home location using PPP over Ethernet PPPoE Which of the following protocols is used by cable modems fo
111. de whether you really need to read the entire chapter If you already intend to read the entire chapter you do not necessarily need to answer these questions now The 15 question quiz derived from the major sections in the Foundation Topics portion of the chapter helps you determine how to spend your limited study time 430 Chapter 15 Remote Access Technologies Table 15 1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions that correspond to those topics Table 15 1 Do I Know This Already Foundation Topics Section to Question Mapping Foundations Topics Section Questions Covered in This Section Perspectives on the PSTN 1 2 Analog Modems 3 4 ISDN 5 7 DSL 8 10 Cable Modems 11 12 Comparisons of Remote Access Technologies 13 15 CAUTION The goal of self assessment is to gauge your mastery of the topics in this chapter If you do not know the answer to a question or are only partially sure of the answer you should mark this question wrong for purposes of the self assessment Giving yourself credit for an answer that you correctly guess skews your self assessment results and might provide you with a false sense of security 1 Which of the following acronyms identifies a voice codec used to encode analog voice signals into a 64 kbps digital data stream a PSTN b MCNS ce ADSL d PCM e AS CELP 2 How many DS
112. e a more realistic perspective on which routes are truly the best routes Support for VLSM Variable length subnet masking VLSM means that in a single Class A B or C network multiple subnet masks can be used The advantage of VLSM is that it enables you to vary the size of each subnet based on the needs of that subnet For instance a point to point serial link needs only two IP addresses so a subnet mask of 255 255 255 252 which allows only two valid IP addresses meets the requirements but does not waste IP addresses A mask allowing a much larger number of IP addresses then can be used on each LAN based subnet Some routing protocols support VLSM and some do not Classless or classful Classless routing protocols transmit the subnet mask along with each route in the routing updates sent by that protocol Classful routing protocols do not transmit mask information So only classful routing protocols support VLSM To say that a routing protocol is classless is to say that it does support VLSM and vice versa 424 Chapter 14 Introduction to Dynamic Routing Protocols Table 14 9 summarizes the most important points of comparison between the interior routing protocols Table 14 9 Interior IP Routing Protocols Compared Summary Supports VLSM Period for Routing Convergence and Is a Classless Full routing Protocol Metric Speed Routing Protocol Updates RIP 1 Hop count Slow No 3
113. e Switch w PCM Andy s House Mayberry CO In the home a DSL modem or DSL capable router is connected to the phone line the local loop using a typical telephone cable The cable uses RJ 11 connectors as is typical for a cable for an analog phone or a modem with pin 3 for transmit and pin 4 for receive The DSL modem understands the Layer 1 encoding details for DSL and encodes the data correctly DSL routers might include the DSL modem feature as well as providing other 456 Chapter 15 Remote Access Technologies features such as IP routing allowing the home user to connect multiple PCs in the home to the Internet at the same time DSL allows a concurrent voice call at the same time as allowing an always on Internet connection The figure shows an analog phone and a DSL modem connected to a single wall plate with two receptacles Physically you connect your DSL modem to a wall socket just like any of the phones in your house The phone generates an analog signal at frequency ranges between 0 and 4000 Hz the DSL modem uses frequencies higher than 4000 Hz so that they do not interfere with each other very much You typically need to put a filter between each phone and the wall socket not shown to prevent interference The same wiring can be used in the local loop as was used for normal telephone service but now the CO connects the local loop wiring to a device called a DSLAM The DSLAM splits the data and voice signals from the local loop
114. e frequency bands for transferring data It s a little like having an Internet channel to go along with CNN TBS ESPN The Cartoon Network and all your other favorite cable channels To appreciate how cable modems work you need a little perspective on some cable TV terminology Cable TV traditionally has been a one way service the cable provider sends electrical signals down the cable for all the channels All you have to do after the physical installation is complete is choose the channel you want to watch While you are watching The Cartoon Network the electrical signals for CNN still are coming into your house over the cable your TV is just ignoring that part of the signal If you have two TVs in your house you can watch two different channels because the signals for all the channels are being sent down the cable Cable TV technology has its own set of terminology just like most of the other access technologies covered in this chapter Figure 15 15 outlines some of the key terms The cable head end site is a main site that receives the programming Programming typically is received via a satellite receiver dish The head end converts the signals to match the correct encoding and frequencies used on the cable and transmits the signals It also might scramble channels that require an extra fee from subscribers so that you have to get a descrambler typically called a set top box from the CATV company Cable Modems 461 Figu
115. e just logged in at the console of R1 and you Telnet to routers R2 R3 and R4 in succession but you suspended your Telnet connection each time in other words all three Telnet connections go from R1 to the other three routers respectively What options do you have for reconnecting to R4 Answer You can use the resume 3 command or just use the 3 command Or you can simply press Enter which resumes your connection to the last suspended Telnet connection in this case R4 16 List the five key pieces of information that can be gathered using CDP as mentioned in the chapter Answer Device identifier address list port identifier capabilities list and platform 17 Imagine a network with Switch1 connected to Router1 with a point to point serial link to Router2 which in turn is connected to Switch2 Assuming that you are logged into R1 what commands could be used to find the IP addresses of Router2 and Switch1 without logging in to either device Chapter 14 555 Answer On Router1 you could use either the show cdp neighbor detail command or the show cdp entry command Both commands list IP addresses of the neighboring devices assuming that CDP is up and working 18 Imagine that a network with Switch1 is connected to Router1 with a point to point serial link to Router2 which in turn is connected to Switch2 You can log in only to Switch1 Which of the other devices could Switch1 learn about using CDP Why Answer Switch
116. ect to an ISP is considered to be an always on service a b c d Analog modems ISDN DSL Cable modems The answers to the Do I Know This Already quiz are found in Appendix A Answers to the Do I Know This Already Quizzes and Q amp A Sections The suggested choices for your next step are as follows m 12 or less overall score Read the entire chapter This includes the Foundation Topics and Foundation Summary sections and the Q amp A section m 13 15 overall score If you want more review on these topics skip to the Foundation Summary section and then go to the Q amp A section Otherwise move to the next chapter Perspectives onthe PSTN 435 Foundation Topics Many companies like the idea of letting workers telecommute working out of their houses To gain access to applications residing at the corporate site companies can support various types of dynamic access to the corporate network for the home user For instance a home based worker might use a modem to dial into the corporate site At the same time most corporations today connect to the Internet using a leased WAN connection of some kind typically one or more T1 circuits or possibly even T3 circuits If their home based users have access to the Internet the users could be allowed to access the necessary corporate applications and data through their Internet connection Depending on the geography fees for Internet
117. ed Read RFC 1112 The Internet Group Message Protocol IGMP for related information about the use of Ethernet multicast in conjunction with IP multicast For example the broadcast address is FFFE FFFF FFFF and one sample multicast address is 0100 5e00 0001 Explain the function of the loopback and collision detection features of an Ethernet NIC in relation to half duplex and full duplex operations Answer The loopback feature copies the transmitted frame back onto the receive pin on the NIC interface The collision detection logic compares the received frame to the transmitted frame during transmission if the signals do not match a collision is occurring With full duplex operation collisions cannot occur so the loopback and collision detection features are purposefully disabled and concurrent transmission and reception is allowed 506 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections Chapter 4 Do Know This Already Quiz 1 Which of the following best describes the main function of OSI Layer 1 protocols Answer B 2 Which of the following typically connects to a four wire line provided by a telco Answer B 3 Which of the following typically connects to a V 35 or RS 232 end of a cable when cabling a leased line Answer B 4 Which of the following functions of OSI Layer 2 is specified by the protocol standard for PPP but is implemented with a Cisco proprietary header field f
118. ed all the configuration on a router and reloaded it To configure the router to use a DNS at IP address 10 1 1 1 which of the following commands is required a ip name server 10 1 1 1 b ip dns 10 1 1 1 c ip domain lookup d ip dns lookup 10 Imagine that you just logged in to the console of router R1 and then Telnetted to R2 What must you type to suspend your Telnet connection going back to R1 a suspend b Ctrl z c Ctrl Shift 6 then x d quit Do Know This Already Quiz 367 The answers to the Do I Know This Already quiz are found in Appendix A Answers to the Do I Know This Already Quizzes and Q amp A Sections The suggested choices for your next step are as follows 8 or less overall score Read the entire chapter This includes the Foundation Topics and Foundation Summary sections and the Q amp A section 9or 10 overall score If you want more review on these topics skip to the Foundation Summary section and then go to the Q amp A section Otherwise move to the next chapter 368 Chapter 13 Basic Router Configuration and Operation Foundation Topics Configuring IP Addresses You easily can configure a Cisco router to forward IP traffic when you understand IP addressing and the IOS configuration process described in Chapter 7 Operating Cisco Routers This chapter shows you examples of a variety of commands used to configure and troubleshoot the rou
119. ed on the destination address of each frame The switch operates at the data link layer of the Open System Interconnections OSI reference model synchronous The imposition of time ordering on a bit stream Practically a device will try to use the same speed as another device on the other end of a serial link However by examining transitions between voltage states on the link the device can notice slight variations in the speed on each end and can adjust its speed accordingly user mode 589 T1 A line from the telco that allows transmission of data at 1 544 Mbps TCP Transmission Control Protocol A connection oriented transport layer TCP IP protocol that provides reliable data transmission TCP IP Transmission Control Protocol Internet Protocol A common name for the suite of protocols developed by the U S Department of Defense in the 1970s to support the construction of worldwide internetworks TCP and IP are the two best known protocols in the suite telco A common abbreviation for telephone company Telnet The standard terminal emulation protocol in the TCP IP protocol stack Telnet is used for remote terminal connection enabling users to log in to remote systems and use resources as if they were connected to a local system Telnet is defined in RFC 854 trace Short for traceroute A program available on many systems that traces the path that a packet takes to a destination It is used mostly to debug routing problems between h
120. een carrier equipment and CPE Diffusing Update Algorithm DUAL The process by which EIGRP routers collectively calculate the routes to place into the routing tables Dijkstra Shortest Path First SPF algorithm Magic math used by link state protocols such as OSPF when the routing table is calculated directed broadcast address Same thing as broadcast address distance vector The logic behind the behavior of some interior routing protocols such as RIP and IGRP Distance vector routing algorithms call for each router to send its entire routing table in each update but only to its neighbors Distance vector routing algorithms can be prone to routing loops but are computationally simpler than link state routing algorithms Also called Bellman Ford routing algorithm DNS Domain Name System A system used on the Internet for translating names of network nodes into addresses DSL Digital subscriber line Public network technology that delivers high bandwidth over conventional copper wiring at limited distances The most common types of DSL are ADSL HDSL SDSL and VDSL Because most DSL technologies do not use the complete bandwidth of the twisted pair there is room remaining for a voice channel E1 Similar to a T1 but used in Europe It uses a rate of 2 048 Mbps and 32 64 kbps channels Flash 581 enable mode Inside the Cisco IOS Software CLI a user can move among various modes Enable mode also called enable EXEC mode allows the us
121. em would modulate or change between the two frequency levels to imply a binary 1 or 0 To achieve a particular bit rate the sending modem would modulate the signal at that rate For instance to send 9600 bps the sending modem would change the signal as necessary every 1 9600th of a second Similarly the receiving modem would sample the incoming analog signal every 1 9600th of a second interpreting the signal as a binary 1 or 0 The process of the receiving end is called demodulation The term modem is a shortened version of the combination of the two words modulation and demodulation Modems must work over the existing PSTN Figure 15 5 outlines the basic process Figure 15 5 Basic Operation of Modems over PSTN Andy s Modem Converts Digital gt Analog PSTN PCM Codec Converts Analog gt Digital Local Loop Analog PCM Codec Converts Digital gt Analog Telco Voice Switch Digital T1 Line 1 DSO Channel Used Barney s Local Loop PC Analog Modem Converts Analog gt Digital Mayberry CO Telco Voice Switch Raleigh CO 442 Chapter 15 Remote Access Technologies First a circuit call must be established One modem signals the phone number for the call in the same way that a telephone does today by sending the tones associated with the keys on a telephone keypad The CO switch interprets these tones calle
122. enable password or enable secret The password in the enable command is not encrypted by default The enable secret password is encrypted using MDS 20 To have the correct syntax what must you add to the following configuration command banner This is Ivan Denisovich s Gorno Router Do Not Use Answer This command does not use a delimiter character at the beginning and end of the text The correct syntax follows banner This is Ivan Do Not Use Answer As typed IOS would think that the letter T was the delimiter character so the banner actually would be his is Ivan Denisovich s Gorno Rou The motd parameter is not shown because it is not required An alternate correct command would be this banner motd This is Ivan Do Not Use 21 22 23 24 25 26 Chapter7 523 Name two commands that affect the text used as the command prompt Answer hostname and prompt When using setup mode you are prompted at the end of the process for whether you want to use the configuration parameters that you just typed in Which type of memory is this configuration stored in if you type yes Answer Both NVRAM and RAM Setup is the only IOS feature that modifies both the active and the startup configuration files as the result of one action by the user What two methods could a router administrator use to cause a router to load IOS stored in ROM Answer Setting the configuration register boot field to binary
123. ency signal might mean 01 Table 15 2 lists the four combinations possible with this example combined modulation scheme Table 15 2 Combinations of Bits with FM and AM Together Amplitude Frequency Used for This Binary Code Low Low 00 Low High 01 High Low 10 High High 11 The modulation scheme in Graph D of Figure 15 6 provides a good context from which to understand the term baud To achieve higher bit rates modems tend to use modulation techniques that encode more than 1 bit in the signal as in this example For instance to achieve 28 kbps with this last modulation scheme the modems would need to change sender or sample receiver the analog signal only every 1 14 000th of a second because each sample represents 2 bits The term baud refers to a single encoded energy signal that can represent 1 or more bits In this final example a baud happens to represent 2 bits Baud is not an acronym it is taken from the name of the inventor Baudot of one of the first modulation schemes that implied more than 1 bit So the modem running at 28 000 bps with a modulation scheme that sends receives 2 bits per baud is running at 14 000 baud per second Point to Point Protocol Features with Modems Most computers today use PPP as the data link protocol when using modems Modems essentially provide an OSI Layer 1 service supporting the transmission and reception of a serial bit stream In fact a dialed circuit between
124. ent by the ping command Answer B Imagine that you just erased all the configuration on a router and reloaded it To configure the router to use a DNS at IP address 10 1 1 1 which of the following commands is required Answer A Imagine that you just logged in to the console of router R1 and then Telnetted to R2 What must you type to suspend your Telnet connection going back to R1 Answer C Create a minimal configuration enabling IP on each interface on a 2501 router two serial one Ethernet The NIC assigned you network 8 0 0 0 Your boss says that you need at most 200 hosts per subnet You decide against using VLSM Your boss also says to plan your subnets so that you can have as many subnets as possible rather than allow 552 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections for larger subnets later When choosing the actual IP address values and subnet numbers you decide to start with the lowest numerical values Assume that point to point serial links will be attached to this router interface ethernet ip address 8 0 1 1 255 255 255 0 interface serial 0 ip address 8 0 2 1 255 255 255 0 interface serial 1 ip address 8 0 3 1 255 255 255 0 Answer The zero subnet was not used in this solution If desired the ip subnet zero global command could have been used enabling subnet 8 0 0 0 24 as well as subnets 8 0 1 0 24 and 8 0 2 0 24 to be used as the three subnets in the configura
125. eparated by several routers What are the largest entities that make it from PC1 to PC2 Answer C and E 3 Which of the following does a router normally use when making a decision about routing TCP IP Answer C 4 Imagine a network with two routers that are connected with a point to point HDLC serial link Each router has an Ethernet with PC1 sharing the Ethernet with Router1 and PC2 sharing an Ethernet with Router2 When PC1 sends data to PC2 which of the following is true Answer A 5 Which of the following are valid Class C IP addresses Answer B 6 What is the range for the values of the first octet for Class A IP networks Answer D 7 PC1 and PC2 are on two different Ethernets that are separated by an IP router PC1 s IP address is 10 1 1 1 and no subnetting is used Which of the following addresses could be used for PC2 Answer D and F 8 How many valid host IP addresses does each Class B network contain Answer D 9 How many valid host IP addresses does each Class C network contain Answer G 10 Which of the following protocols allows a client PC to discover the IP address of another computer based on that other computer s name Answer C Q amp A 11 12 Chapter5 511 Which of the following protocols allow a client PC to request assignment of an IP address as well as learn its default gateway Answer D Which term is defined by the following phrase the type of protocol th
126. er would each be in a different broadcast domain A switch can create multiple broadcast domains by creating multiple VLANs but a router must be used to route packets between the VLANs Define the term VLAN Answer Virtual LAN VLAN refers to the process of treating one subset of a switch s interfaces as one broadcast domain Broadcasts from one VLAN are not forwarded to other VLANs unicasts between VLANs must use a router Advanced methods such as Layer 3 switching can be used to allow the LAN switch to forward traffic between VLANs without each individual frame being routed by a router 536 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 4 If two Cisco LAN switches are connected using Fast Ethernet what VLAN trunking protocols could be used If only one VLAN spanned both switches is a VLAN trunking protocol needed Answer ISL and 802 1q are the trunking protocols used by Cisco over Fast Ethernet If only one VLAN spans the two switches a trunking protocol is not needed Trunking or tagging protocols are used to tag a frame as being in a particular VLAN if only one VLAN is used tagging is unnecessary 5 Must all members of the same VLAN be in the same collision domain the same broadcast domain or both Answer By definition members of the same VLAN are all part of the same broadcast domain They might all be in the same collision domain but only if all devices in the VLAN are connec
127. er command prompt using the PC you will most likely use when studying That way when you are ready to do your first lab or scenario you know you have worked out any installation issues If you intend to do most of the labs and scenarios you might want to print CD only Appendixes B and C Decide if you prefer to do the labs and scenarios after reading the book or as you go along If you want to do the labs as you progress through the book refer to Table C 2 for my suggestions on the best time to do the labs and scenarios Considerations When Using NetSim 575 Table C 2 The Best Time to Do Each Lab or Scenario Using NetSim After Reading Scenario or Lab Location Topic Which Chapter Scenario Chapter Chapter 16 Comprehensive scenario for 16 16 of this book topics in this book Scenario 3 CD only Appendix B LAN switch basic 8 configuration Scenario 6 CD only Appendix B Subnet design with a ClassB 12 network Lab 1 CD only Appendix C Router command line 7 interface familiarization Lab 2 CD only Appendix C 2950 series switch command 8 line interface familiarization Lab 3 CD only Appendix C Basic router IP configuration 13 and management navigation Considerations When Using NetSim NetSim is a wonderful product and you can certainly get a lot of good hands on experience using the NetSim product that is included with the book However like any simulator product it does not mimic a
128. er to use the most powerful and potentially disruptive commands on a router encapsulation The wrapping of data in a particular protocol header For example an IP packet could be encapsulated in an Ethernet header and trailer before being sent over an Ethernet encryption Applying a specific algorithm to data to alter the appearance of the data making it incomprehensible to those who are not authorized to see the information error recovery The process of noticing when some transmitted data was not successfully received and resending the data until it is successfully received Ethernet A baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox Intel and Digital Equipment Corporation Ethernet networks use CSMA CD and run over a variety of cable types exterior routing protocol A routing protocol designed for use between two different organizations These typically are used between ISPs or between a company and an ISP For example a company would run BGP an exterior routing protocol between one of its routers and a router inside an ISP FCIP Fibre Channel over IP A protocol for sending Fibre Channel protocols over an IP network Fibre Channel A technology for transmitting data between computer devices at data rates from 100 MBps to 400 MBps over optical fiber or copper Fibre Channel is optimized for connecting servers to shared storage devices and for interconnecting storage controllers and drives
129. erface fastEthernet 0 1 SW3 config if description trunk to SW1 SW3 config if interface fastethernet 0 2 SW3 config if description trunk to SW2 SwW3 config if Z SW3 SW3 copy running config startup config Destination filename startup config Building configuration OK SW3 Scenario Part C Verification and Questions The INTRO exam tests you on your memory of the kinds of information you can find in the output of various show commands Using Examples 16 5 16 6 and 16 7 as references answer the questions following the examples NOTE Inthe network from which these commands were captured several administrative settings not mentioned in the scenario were configured For example the enable password was configured So the configurations might contain additional items not specifically mentioned in the instructions but none of those impact the actual behavior of the features discussed in the scenario Example Example Scenario Part A Planning 489 16 5 Scenario Part C R1 show and debug Output Ri show ip interface brief Interface IP Address OK Method Status Protocol Seriald 163 1 12 201 YES NVRAM up up Seriali 163 1 13 201 YES NVRAM up up Ethernet 163 1 1 201 YES NVRAM up up Ri show access lists Standard IP access list 83 deny 163 1 3 0 wildcard bits 0 0 0 127 permit any R1 16 6 Part C R2 show and debug Output R2 show interface Serial is up line protocol is up Hardware is H
130. ers with PPP in use What are the names of the protocols inside PPP that would be used on this link What are their main functions Answer The PPP Link Control Protocol LCP controls and manages the link The IP Control Protocol IPCP also would be used because you need a CP for each Layer 3 protocol IPCP can assign IP addresses to devices on the other end of a link 15 What are some of the main similarities between Frame Relay and ATM Answer Both use an access link to access the service provider Both use the concept of a virtual circuit between DTE devices And both allow multiple VCs to cross a single access link 16 Compare and contrast ATM and SONET in terms of the OSI model Answer SONET defines the Layer 1 details of passing traffic over optical cabling whereas ATM provides the Layer 2 functionality including link specific addressing framing and error detection 17 Besides HDLC and PPP list the other four serial point to point data link protocols covered in this chapter Answer SDLC LAPB LAPD and LAPF 18 List the speeds of a T1 line E1 OC 3 and OC 12 Answer 1 544 Mbps 2 048 Mbps 155 Mbps and 622 Mbps Chapter 5 Do Know This Already Quiz 1 Which of the following describes the functions of OSI Layer 3 protocols Answer A and C 510 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 2 Imagine that PC1 needs to send some data to PC2 and PC1 and PC2 are s
131. ersion 12 1 11 EA1 RELEASE SOFTWARE fc1 Copyright 1986 2002 by cisco Systems Inc Compiled Wed 28 Aug 2 10 03 by antonino advertisement version 2 Protocol Hello OUI 0x 0000C Protocol ID 0x0112 payload len 27 value 0000000 QOFFFFFFFFO10231FF000000000000000AB7DCB780FFQ000 VTP Management Domain Native VLAN 1 Duplex half Seville show cdp interface Ethernet is up line protocol is down Encapsulation ARPA Sending CDP packets every 60 seconds Holdtime is 180 seconds Serial 2 is up line protocol is up Encapsulation FRAME RELAY Sending CDP packets every 60 seconds Holdtime is 180 seconds Seriali is up line protocol is up Encapsulation HDLC Sending CDP packets every 60 seconds Holdtime is 180 seconds Seville show cdp traffic CDP counters Total packets output 31 Input 41 Hdr syntax 0 Chksum error Encaps failed 9 No memory 0 Invalid packet 0 Fragmented 0 CDP version 1 advertisements output Input 0 CDP version 2 advertisements output 31 Input 41 The commands provide information about both the neighbors and the behavior of the CDP protocol itself The show cdp command has four options as shown at the beginning of the example For instace the show cdp neighbor command lists each neighbor with one line of output per neighbor Notice that Seville has two router neighbors denoted by the R and one switch in this case a 3550 denoted with an S Next in the example you see two commands t
132. ersion Table Decimal Value Binary Value Decimal Value Binary Value 46 0010 1110 76 0100 1100 47 0010 1111 Th 0100 1101 48 0011 0000 78 0100 1110 49 0011 0001 79 0100 1111 50 0011 0010 80 0101 0000 51 0011 0011 81 0101 0001 52 0011 0100 82 0101 0010 53 0011 0101 83 0101 0011 54 0011 0110 84 0101 0100 55 0011 0111 85 0101 0101 56 0011 1000 86 0101 0110 57 0011 1001 87 0101 0111 58 0011 1010 88 0101 1000 59 0011 1011 89 0101 1001 60 0011 1100 90 0101 1010 61 0011 1101 91 0101 1011 62 0011 1110 92 0101 1100 63 0011 1111 93 0101 1101 64 0100 0000 94 0101 1110 65 0100 0001 95 0101 1111 66 0100 0010 96 0110 0000 67 0100 0011 97 0110 0001 68 0100 0100 98 0110 0010 69 0100 0101 99 0110 0011 70 0100 0110 100 0110 0100 71 0100 0111 101 0110 0101 72 0100 1000 102 0110 0110 73 0100 1001 103 0110 0111 74 0100 1010 104 0110 1000 75 0100 1011 105 0110 1001 Decimal to Binary Conversion Table Decimal Value Binary Value Decimal Value Binary Value 106 0110 1010 136 1000 1000 107 0110 1011 137 1000 1001 108 0110 1100 138 1000 1010 109 0110 1101 139 1000 1011 110 0110 1110 140 1000 1100 111 0110 1111 141 1000 1101 112 0111 0000 142 1000 1110 113 0111 0001 143 1000 1111 114 0111 0010 144 1001 0000 115 0111 0011 145 1001 0001 116 0111 0
133. es like 10BASE something specifically state the need for four pairs of wires in the cable What about for Gigabit Ethernet Answer 100BASE T4 for Fast Ethernet and 1000BASE T for Gigabit Ethernet 13 Which variations on the Fast Ethernet and Gigabit standard use IEEE 802 3 MAC and 802 2 LLC framing Answer All of them 14 What were some of the differences between 10 Gigabit Ethernet as compared with other types of Ethernet as outlined in this chapter Answer The speed of course is the obvious difference Additionally 10 Gigabit Ethernet is allowed to be used in a point to point topology only it supports full duplex only and today it supports only optical cabling 15 What IEEE standards are used by an 802 11 access point Answer The access point uses 802 11 standards for communication across the wireless LAN including 802 2 LLC It also connects to a wired LAN so it uses 802 3 for its wired Ethernet 16 What does the term line of sight mean in relation to wireless communications Answer Line of sight means that you could stand beside one device and see the other device Some wireless technologies require a line of sight and others do not Chapter 12 Do Know This Already Quiz 1 Which of the following is the result of a Boolean AND between IP address 150 150 4 100 mask 255 255 192 0 Answer B 2 If mask 255 255 255 128 were used with a Class B network how many subnets could exist with
134. ess of changing or modulating the amplitude is called amplitude modulation Modulation as defined by www dictionary com is the variation of a property of an electromagnetic wave or signal such as its amplitude frequency or phase which is exactly what amplitude modulation does specifically for the amplitude Graph B in Figure 15 6 depicts frequency modulation In this simple example the higher frequency the part with the curved lines closer together means 0 and the lower frequency means 1 Notice that the amplitude stays the same in that case so this modem standard simply changes the frequency to imply a 1 or a 0 So if the modems are running at 28 kbps then every 1 28 000th of a second the modem would make the frequency high or low to encode a binary 0 or 1 Graph C in Figure 15 6 depicts phase modulation Phase modulation changes the phase of the signal instead of the signal following its normal pattern of rising to the highest positive voltage gradually lowering to the lowest voltage and back again the signal changes directions which changes the phase Modems can modulate the phase to imply a binary 0 or 1 as well Finally Graph D in Figure 15 6 shows a combination of frequency modulation and amplitude modulation With this final scheme each signal represents 2 bits For instance a 444 Chapter 15 Remote Access Technologies low amplitude and low frequency signal might mean 00 whereas a low amplitude but high frequ
135. etbits Number of Number of Number of Network and Network Number of Subnet Hosts per Number of Mask Bits Host Bits Bits Subnet Subnets 220 8 7 0 24 4 4 14 14 255 255 255 240 19 You design a network for a customer and the customer insists that you use the same subnet mask on every subnet The customer will use network 10 0 0 0 and needs 200 subnets each with 200 hosts maximum What subnet mask would you use to allow the largest amount of growth in subnets Which mask would work and would allow for the most growth in the number of hosts per subnet Answer Network 10 0 0 0 is a Class A network so you have 24 host bits with no subnetting To number 200 subnets you will need at least 8 subnet bits because 2 is 256 Likewise to number 200 hosts per subnet you will need 8 host bits So you need to pick a mask with at least 8 subnet bits and 8 host bits 255 255 0 0 is a mask with 8 subnet bits and 16 host bits That would allow for the 200 subnets and 200 hosts while allowing the number of hosts per subnet to grow to 216 2 quite a large number Similarly a mask of 255 255 255 0 gives you 16 subnet bits allowing 216 2 subnets each with 2 2 hosts per subnet 20 Referring to Figure A 1 Fred has been configured with IP address 10 1 1 1 Router A s Ethernet has been configured with 10 1 1 100 Router A s Serial interface uses 10 1 1 101 Router B s serial uses 10 1 1 102 Router B s Etherne
136. etric might be a better option 6 Compare the V 90 and V 92 modem specifications 7 Compare analog modems ISDN BRIs DSL and cable modems in terms of concurrent support for voice and data 8 Compare analog modems ISDN BRIs DSL and cable modems in terms of whether the data service is always on 9 List some of the pros and cons regarding the use of analog modems for remote access 10 List some of the pros and cons regarding the use of ISDN for remote access 11 List some of the pros and cons regarding the use of DSL for remote access 12 Define what the acronym DSLAM stands for and explain the concept behind how a DSLAM allows voice and data to flow over the same local loop phone line 13 Which of the DSL standards is the most common in the United States today What is the range of upstream and downstream speeds for that type of DSL as well as the maximum distance of the local loop 14 15 16 17 18 19 20 Q amp A 475 What protocols are used by DSL at the data link layer Imagine that Andy and Barney are neighbors and they both use cable modems Describe the type of traffic that they could generate that could cause collisions and tell what is done to help prevent those collisions Name the four different Layer 1 encoding methods defined for use by cable modems For each one list whether it is used for upstream data downstream data or both Which of the four different remote access technologies
137. eventing loops The routes added to the routing table include a subnet number the interface out which to forward packets so that they are delivered to that subnet and the IP address of the next router that should receive packets destined for that subnet if needed An analogy about routing protocols can help Imagine that a stubborn man is taking a trip to somewhere he has never been He might look for a road sign referring to the destination town and pointing him to the next turn By repeating the process at each intersection he eventually should make it to the correct town Of course if a routing loop occurs in other words he s lost and he stubbornly never asks for directions he could drive around forever or at least until he runs out of gas In this analogy the guy in the car is like a routed 408 Chapter 14 Introduction to Dynamic Routing Protocols protocol it travels through the network from the source to the destination The routing protocol is like the fellow whose job it is to decide what to paint on the various road signs As long as all the road signs have correct information the guy in the car should make it to the right town just by reading the road signs Likewise as long as the routing protocol puts the right routes in the various routing tables the routers should deliver packets successfully All routing protocols have several general goals as summarized in the following list m To dynamically learn and fill the ro
138. ewYork gt NewYork gt Note User pressed Ctrl Shift 6 and then x Cincy disconnect 2 Done with New York terminate Telnet Closing connection to NewYork confirm Just press Enter to confirm Cincy The play by play notes in the example explain most of the details Example 13 10 begins with the Cincy command prompt that would be seen in Bench s Telnet window because the user at Bench Telnetted into Cincy first After Telnetting to Milwaukee the Telnet connection was suspended Then after Telnetting to New York that connection was suspended The two connections can be suspended or resumed easily The resume command can be used to resume either connection however the resume command requires a connection ID which is shown in the show sessions command The where command provides the same output Also instead of using the resume command you can just use the session number as a command For instance just typing the command 2 does the same thing as typing the command resume 2 The interesting and potentially dangerous nuance here is that if a Telnet session is suspended and you simply press Enter Cisco IOS Software resumes the connection to the most recently suspended Telnet connection That is fine until you realize how much you tend to press the Enter key occasionally to clear some of the clutter from the screen With a suspended Telnet connection you also just happened to reconnect to another router This is particularly danger
139. exam topics PART V Wide Area Networking Chapter 15 Remote Access Technologies This chapter covers the following subjects m Perspectives on the PSTN m Analog Modems m Integrated Services Digital Network m Digital Subscriber Line m Cable Modems Comparison of Remote Access Technologies cuapter 1O Remote Access Technologies Earlier in this book you learned about Ethernet LANs point to point WAN links and Frame Relay All of these technologies can be used to connect a corporate site to the Internet However none of these options is cost effective for connecting the typical home based user to the Internet In this chapter you will learn about several different technologies used for Internet access from the home Some of these same technologies can be used to remotely access corporate networks as well This chapter covers the most common remote access technologies namely analog modems DSL ISDN and cable AUTHOR S NOTE While they may be on the CCNA exam the topics in this chapter are less likely to be on the CCNA exam than most other topics in this book For those of you that are planning to take the CCNA exam instead of taking both the INTRO and ICND exams you might consider skipping this chapter Refer to the introduction to this book for more perspectives on the CCNA exam topics Do I Know This Already Quiz The purpose of the Do I Know This Already quiz is to help you deci
140. f channel For instance BRIs are referred to as 2B D meaning two B channels and one D channel PRIs based on T 1 framing as in the United States are referred to as 23B D and PRIs based on E 1 framing typically found in Europe are referred to as 30B D E 1s have 32 DSO channels with 1 reserved for framing and 1 used for the D channel when used as a PRI that leaves 30 DSO channels as B channels Table 15 4 lists the number of channels for each type of ISDN line and the terminology used to describe them Table 15 4 BRI and PRI B and D Channels Type of Number of Bearer Number of Signaling Interface Channels B Channels Channels D Channels Descriptive Term BRI 2 1 16 kbps 2B D PRI T1 23 1 64 kbps 23B D PRI E1 130 1 64 kbps 30B D ISDN Call Setup and Data Link Protocols Call setup differs between ISDN and modems With a telephone call and with analog modems DTMF tones are sent across the analog local loop to the telco The telco switch at the local CO interprets the dialed digits and sets up the call However with ISDN there is no analog local loop over which the analog DTMF tones can be sent 450 Chapter 15 Remote Access Technologies ISDN devices send and receive signaling messages to and from the local ISDN switch to which it is connected In telco terminology signaling refers to any type of request to establish a circuit So punching keys on your telephone is considered signaling to set up
141. fact some people say things like That modem runs at 33 kilo baud per second really meaning 33 kilobits per second kbps thinking that bits per second and baud per second are the same thing But the two terms are not synonymous as you will read shortly Modems create an analog signal when sending data As mentioned earlier analog electrical signals can be analyzed in terms of frequency amplitude and phase So modem standards define that particular values for these three parts of the signal imply a 1 or a 0 To appreciate what that means consider the two parts of Figure 15 6 Analog Modems 443 Figure 15 6 Amplitude Frequency and Phase Modulation Volume i High High AA Low Time Y V Amplitude Modulation O 1 0 1 Low High Low B AMMA Time U WVVYe y 0110 Frequency Modulation Phase Shifts c A Lp An Time W 4 Phase Modulation O 1 0 1 Time 5 Ra oe AM FM Combined 00 01 10 11 The figure depicts some very simple ways that a modem could be used to create an analog signal that can be interpreted by the receiver as a set of binary digits In Graph A a low amplitude means a binary 0 and a high amplitude means a binary 1 All the sending modem has to do is modulate change the amplitude of the signal to imply a 1 or a 0 For instance if the modem was running at 28 kbps then every 1 28 000th of a second it would make the amplitude of the signal low or high to encode a binary 0 or 1 The proc
142. fic between the VLANs Q amp A Chapter 10 535 Which of the following terms refers to a function that can forward traffic between two different VLANs Answer B and C Layer 2 switching forwards frames only inside a single VLAN Layer 3 switching and Layer 4 switching forward traffic between VLANs either based on the Layer 3 destination address Layer 3 switching or the Layer 4 port numbers Layer 4 switching Imagine a small campus network with three VLANs spread across two switches Which of the following would you expect to also have a quantity of 3 Answer B and C By definition a VLAN is a set of devices in the same broadcast domain An IP subnet on a LAN is typically comprised of devices in the same VLAN Which of the following are considered to be ways of configuring VLANs Answer A and B Define the term collision domain Answer A collision domain is a set of Ethernet devices for which concurrent transmission of a frame by any two of them will result in a collision Bridges switches and routers separate LAN segments into different collision domains Repeaters and shared hubs do not separate segments into different collision domains Define the term broadcast domain Answer A broadcast domain is a set of Ethernet devices for which a broadcast sent by any one of them should be received by all others in the group Unlike routers bridges and switches do not stop the flow of broadcasts Two segments separated by a rout
143. figuration The command can be typed from any part of configuration mode The login command which follows the line console 0 command tells IOS that a password prompt is desired at the console 10 11 12 13 Chapter8 527 What configuration command is used to tell the switch the password that is required at the console What configuration mode context must you be in That is what command s must you type before this command after entering configuration mode List the commands in the order in which they must be typed while in config mode line console 0 password XXXXXXX Answer The password command tells IOS the value that should be typed when a user wants access from the console This value is requested by IOS because of the login command The password xxxxxxx must be typed while in console configuration mode which is reached by typing line console 0 What are the primary purposes of Flash memory in a Cisco switch Answer To store IOS and microcode files In most switches only IOS is stored in flash If microcode is upgraded the files also reside in Flash memory What is the intended purpose of NVRAM memory in a Cisco 2950 switch Answer To store a single configuration file used at switch load time NVRAM does not support multiple files What does the NV stand for in NVRAM Answer Nonvolatile NVRAM is battery powered if it is really RAM In some switches Cisco has sneakily used a small portion of Flash memo
144. filter Generally a process or a device that screens network traffic for certain characteristics such as source address destination address or protocol and determines whether to forward or discard that traffic based on the established criteria firewall A device or a software package that separates more secure network components from less secure components protecting the more secure network from inappropriate access Flash A type of permanent memory implemented either with a EEPROM chip or with a PC card that can be easily removed Routers use flash instead of disk drives for storing large files particularly the IOS 582 flow control flow control The process of regulating the amount of data sent by a sending computer towards a receiving computer Several flow control mechanisms exist including TCP flow control which uses windowing forward To send a frame received in one interface out another interface toward its ultimate destination four wire circuit A line from the telco with four wires composed of two twisted pair wires Each pair is used to send in one direction so a four wire circuit allows full duplex communication Frame Relay An industry standard switched data link layer protocol that handles multiple virtual circuits using LAPF encapsulation between connected devices Frame Relay is more efficient than X 25 the protocol for which it generally is considered a replacement frame A logical grouping of information sent
145. formation about other devices on the same LAN or on the remote side of a WAN Runs on all media that support SNAP headers including LANs Frame Relay and ATM media CPE 579 CHAP Challenge Handshake Authentication Protocol A security feature supported on lines using PPP encapsulation that prevents unauthorized access CHAP does not itself prevent unauthorized access it merely identifies the remote end The router or access server then determines whether that user is allowed access CLI Command line interface An interface that enables the user to interact with the operating system by entering commands and optional arguments clock source The device to which the other devices on the link adjust their speed when using synchronous links codec Coder decoder An integrated circuit device that transforms analog voice signals into a digital bit stream and then transforms digital signals back into analog voice signals collision domain A set of network interface cards NICs for which a frame sent by one NIC could result in a collision with a frame sent by any other NIC in the same collision domain configuration mode Inside the Cisco IOS Software CLI a user can move among various modes Configuration mode enables the user to enter configuration commands but not any EXEC commands for instance the user can configure an IP address but cannot show the status of any router features configuration register In Cisco routers a 16 bit user conf
146. fully meshed backbone PCM Pulse code modulation A technique of encoding analog voice into a 64 kbps data stream by sampling with 8 bit resolution at a rate of 8000 times per second PDU Protocol data unit An OSI term to refer generically to a grouping of information by a particular layer of the OSI mode More specifically an LxPDU would imply the data and headers as defined by Layer x ping Packet Internet groper An Internet Control Message Protocol ICMP echo message and its reply ping often is used in IP networks to test the reachability of a network device portnumber A field ina TCP or UDP header that identifies the application that either sent source port or should receive destination port the data inside the data segment PPP Point to Point Protocol A protocol that provides router to router and host to network connections over synchronous and asynchronous circuits prefix notation A shorter way to write a subnet mask in which the number of binary 1s in the mask is simply written in decimal For instance 24 denotes the subnet mask with 24 binary 1 bits in the subnet mask The number of bits of value binary 1 in the mask is considered to be the prefix PRI Primary Rate Interface An Integrated Services Digital Network ISDN interface to primary rate access Primary rate access consists of a single 64 kbps D channel plus 23 T1 or 30 E1 B channels for voice or data Protocol Type field A field in a LAN header that ident
147. g ISDN installation for a home based PC works much like it does for modems The most popular option uses an external ISDN modem or terminal adapter Figure 15 12 depicts the typical cabling Figure 15 12 Cabling a PC to an ISDN TA ISDN 2 Wire modem In this case a COM port shown or a USB port not shown connects to the TA The TA terminates the ISDN cable from the telco The cable from the telco uses an RJ 45 connector the same type used for Ethernet cables However the pins used inside the cable are different than those for Ethernet so do not just grab any old cable with an RJ 45 connector Piins 3 and 6 are used for transmit and pins 4 and 5 used for receive ISDN Summary ISDN supports a BRI service with 2 B channels and a PRI service with either 23 T1 or 30 E1 B channels Signaling for call setup and teardown occurs over an out of band D channel 454 Chapter 15 Remote Access Technologies After a circuit has been established over a B channel ISDN provides a Layer 1 service delivering a serial bit stream between the two endpoints of the circuit ISDN s advantages include the capability to support voice calls concurrently with a data call Also ISDN can be used over the local telco loop with no significant distance limitations And it provides more bandwidth than do modems particularly with both B channels dialed to the same remote site ISDN does have a few disadvantages with the biggest disadvantage being the
148. g UTP cable types support Gigabit Ethernet Answer C D and E Which of the following Ethernet standards call for the use of 802 3 MAC and 802 2 LLC standards Answer E All the Ethernet standards call for the use of 802 3 framing including the 802 3 MAC and 802 2 LLC sublayers 538 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 7 Which of the following Ethernet standards refer to Gigabit Ethernet Answer B and C 802 3z refers to Gigabit over optical and 802 3ab refers to Gigabit over copper cabling 8 Which of the following IEEE standards define framing used when transmitting wireless LAN traffic Answer A and D Wireless LANs use the IEEE 802 11 standard instead of 802 3 for the MAC sublayer header and also use IEEE 802 2 for the LLC sublayer header Q amp A 1 Describe why a 10BASE T network using a hub is considered to be a logical bus topology Answer A physical bus causes the transmitted electrical signal to be propagated to all devices connected to the bus A 10BASE T hub repeats a signal entering one port out all the other ports ensuring that all devices receive the same signal Hubs do not have any logic to prevent some frames from being sent out ports all signals are repeated creating a single collision domain just like a physical bus 2 Compare and contrast full mesh versus partial mesh topologies in relation to physical topologies Answer In a fu
149. h a multilayer switch Describe in what cases the terms could be used synonymously Answer A Layer 3 switch forwards packets based on their destination IP address much like a router but with the forwarding logic performed quickly inside hardware in the switch A multilayer switch performs switching at multiple layers Many Layer 3 switches also perform Layer 2 switching for frames destined to another device in the same VLAN and Layer 3 switching for packets destined to another subnet VLAN The terms are often used synonymously because many people assume that a LAN switch can always perform L2 switching with L3 switching being an additional function Chapter 11 Do I Know This Already Quiz 1 Which of the following network topologies is characterized by attachments from many devices to a single linear cable Answer A Which of the following types of networks is considered to be a logical bus topology Answer A and B 10BASES is a physical bus and it behaves like a bus making it a logical bus topology Because a 10BASE T hub repeats incoming transmissions out all other ports effectively creating a bus it is considered to be a logical bus topology Which pins typically are used on an RJ 45 connector by an Ethernet card to support Fast Ethernet over UTP cabling Answer C Which part of an optical cable reflects the light back into the cable as a result of a different refractive index Answer A Which of the followin
150. hat list details per neighbor The show cdp entry fred command lists the details learned by CDP about the neighbor whose host name is fred Before using the command you would just use the show cdp neighbor command to find the host names of any neighbors that CDP already has found Another command that 396 Chapter 13 Basic Router Configuration and Operation lists the detailed information is the show cdp neighbor detail command which is in the same format as show cdp entry but lists the information for every neighbor You actually can draw a network diagram by using CDP exercising a little patience and issuing the right commands on all the devices in a network Whether you are using the briefer output of show cdp neighbor or the more complete output of show cdp neighbor detail or show cdp entry the output lists both the local interface and the port ID The port ID is the interface number as designated by the other device For instance the switch uses port 0 4 to connect to this device So you literally could piece together the network diagram from the CDP output Foundation Summary 397 Foundation Summary The Foundation Summary section of each chapter lists the most important facts from the chapter Although this section does not list every fact from the chapter that will be on your CCNA exam a well prepared CCNA candidate should know at a minimum all the details in each Foundation Summary before going to take the ex
151. hat will be used the next time the router is reloaded 7 What does CDP stand for Solutions to Part C Verification and Questions The answers to the questions for Part C are as follows 1 The show ip arp command refer to Example 16 7 contains MAC and IP addresses 2 The trace 163 1 1 1 command could be used to find the path that a packet would take from R3 to 163 1 1 1 refer to Example 16 7 3 To change the IP address on an interface use the following steps R3 gt enable password password R38 configure terminal R3 config interface ethernet 494 Chapter 16 Final Preparation R3 config if ip address 10 1 1 1 255 255 255 0 R3 config Ctr1 Z R3 4 To find all commands that start with the letter C do the following R3 c clear clock configure connect copy R3 c 5 The two commands that list the currently used configuration in a router are show running config and write terminal 6 The two commands that list the configuration that will be used the next time the router is reloaded are show startup config and show config 7 CDP stands for Cisco Discovery Protocol PART VII Appendixes Appendix A Answers to the Do I Know This Already Quizzes and O amp A Sections Appendix B Binary Decimal Conversion Chart Appendix C Using the Simulation Software for Hands on Exercises Glossary APPENDIX A Answers to the Do I Know This Already Quizzes and Q amp A Sections Chapter
152. hey serve different purposes PPP provides dynamic address assignment by the ISP for the DSL modem and some basic authentication with Challenge Handshake Authentication Protocol CHAP CHAP is covered in the CCNA ICND Exam Certification Guide and the ICND exam Also depending on the gear installed at a site DSL might require PPP over Ethernet PPPoE for traffic between a PC in the home and the DSL modem router in the home Figure 15 14 shows a typical installation using an ADSL router like the Cisco 827H series The 827H acts as both a router and a DSL modem Figure 15 14 Protocols Used with a DSL Router IP Network Owned by ISP DHCP Client Layer 1 SONET Ethernet DHCP Server ATM VC Layer 2 _ DSLAM a es A DSL Router Local Loop Layer 1 DSL Andy s House Mayberry CO Digital Subscriber Line 459 Any PCs at the home can connect to the DSL router using Ethernet In fact as is common with many DSL routers the Cisco 827H DSL router includes a four port Ethernet hub built into the router so you can just cable a PC directly to the 827H Alternately you can create an Ethernet any way you want as long as there is Ethernet connectivity from the PC to the DSL router A straight through Ethernet cable would be used to connect the PC directly to the DSL router The PC can be configured just like it would be on any other Ethernet thinking of the DSL router like any other router The PC would point to the DS
153. host bits The mask is an important ingredient in the formula to dissect an IP address along with knowledge of the number of network bits implied for Class A B and C networks the mask provides a clear definition of the size of the network subnet and host parts of an address Given the IP address 134 141 7 11 and the mask 255 255 255 0 what is the subnet number Answer The subnet is 134 141 7 0 The binary algorithm is shown in the table that follows Address 134 141 7 11 1000 0110 1000 1101 0000 0111 0000 1011 Mask 255 255 255 0 1111 1111 1111 1111 1111 1111 0000 0000 Result 134 141 7 0 1000 0110 1000 1101 0000 0111 0000 0000 Given the IP address 193 193 7 7 and the mask 255 255 255 0 what is the subnet number Answer The network number is 193 193 7 0 Because this is a Class C address and the mask used is 255 255 255 0 the default no subnetting is in use The binary algorithm is shown in the table that follows Address 193 193 7 7 1100 0001 1100 0001 0000 0111 0000 0111 Mask 255 255 255 0 1111 1111 1111 1111 1111 1111 0000 0000 Result 193 193 7 0 1100 0001 1100 0001 0000 0111 0000 0000 544 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 5 Given the IP address 200 1 1 130 and the mask 255 255 255 224 what is the subnet number Answer The answer is 200 1 1 128 The table that follows shows the subnet chart to help you learn the way to
154. iated higher layer protocols TCP UDP HTTP FTP Telnet DNS DHCP and so on can run over any of these access technologies the differences lie in what is done at Layers 1 and 2 Figure 15 16 outlines the protocols used by each Figure 15 16 The OSI Reference Model and Remote Access Technologies Applications TCP or UDP Applications TCP or UDP IP IP PPP PPP Modem Standards v x ISDN l 430 Standards Applications TCP or UDP Applications ATM Ethernet TCP or UDP xDSL Standards IP IEEE 802 2 MCNS MAG Upstream Downstream QPSK QAM 16 QAM 64 QAM 256 Table 15 8 lists some of the main points for comparison of these technologies Table 15 8 Comparison of Modems ISDN DSL and Cable Analog Modems ISDN DSL Cable Modems Transport Telco line Telco line Telco line CATV cable Supports symmetric Yes Yes Yes No speeds Supports asymmetric Yes No Yes Yes speeds Speed ranges 56 kbps and lower 64 kbps per 56 kbps to 320 kbps to B channel 2 Mbps 40 Mbps continues 466 Chapter 15 Remote Access Technologies Table 15 8 Comparison of Modems ISDN DSL and Cable Continued Cable Modems issues varies Degrades under higher No No No Yes loads Supports IP and Yes Yes Yes Yes associated higher layer protocols Allows concur
155. ically to the DNS server whereas ARP uses a LAN broadcast frame DNS queries supply a name expecting to hear the corresponding IP address back from the server ARP requests supply an IP address hoping to hear a corresponding MAC address not from a server but from the host that uses that IP address Chapter 6 Do I Know This Already Quiz 1 Which of the following protocols are connection oriented Answer A and B 2 Which of the following protocols are reliable Answer B 3 PC1 is using TCP has a window of 4 and sends four segments numbered 2 3 4 and 5 to PC2 PC2 replies with an acknowledgment number 5 What should PC1 do next Answer D 516 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 4 Which of the following are not features of a protocol that is considered to match OSI Layer 4 Answer D 5 Which of the following flow control methods let the receiver tell the sender how much data the sender is allowed to send before the sender must wait for an acknowledgment Answer C 6 Which of the following header fields identifies which TCP IP application gets data received by the computer Answer E and F 7 Which of the TCP connection establishment flows sets both the SYN and ACK flags in the TCP header Answer B 8 Which of the following is not a typical function of TCP Answer D and E 9 Which of the following functions is performed by TCP and UDP Answer C 10
156. ier 12 96 Mbps to 52 8 Mbps 4500 feet data rate DSL in process modulation SCM for both upstream and VDSL downstream speed ISDN DSL ANSI ETR 080 Two binary one quaternary 144 kbps for both 18 000 feet IDSL 2B1Q upstream and downstream speed Symmetric None 2B1Q 768 kbps for both 22 000 feet DSL SDSL upstream and downstream speed High data rate ITU G 991 1 2B1Q 1 544 or 2 048 Mbps for 12 000 feet DSL HDSL ANSI TR 28 both upstream and downstream speed G SHDSL ITU G 991 2 Trellis coded pulse 192 kbps to 2 360 Mbps 28 000 feet Figure 15 20 outlines some of the key terms used with CATV Foundation Summary 471 Figure 15 20 Cable TV Terminology Andy s PC Ethernet mh Cable Modem F connectors pA ESTEE NTT Head end Li 1 Andy s House NG L r ANS i Distribution Cables Mayberry CATV L Drop Cable Table 15 12 summarizes some of the key reference information about downstream CATV data over cable Table 15 12 Downstream Data over Cable Interesting Facts Downstream Rate OSI Layer 1 QAM 64 and QAM 256 encoding OSI Layer 2 MCNS MAC and JEEE 802 2 LLC Multiplexing used Frequency division multiplexing Speed 30 to 40 Mbps 472 Chapter 15 Remote Access Technologies Table 15 13 summarizes some of the key points about the upstream CATV data channel Table 15 13 Upstream Data over Cable Interesting Facts Downstream Rate OSI
157. ifies the type of header that follows the LAN header Includes the DIX Ethernet Type field the IEEE 802 2 DSAP field and the SNAP protocol Type field PSTN Public Switched Telephone Network A general term referring to the variety of telephone networks and services in place worldwide Sometimes called POTS single mode 587 PTT Post telephone and telegraph A government agency that provides telephone services PTTs exist in most areas outside of North America and provide both local and long distance telephone services RAM _ Random access memory A type of volatile memory that can be read and written by a microprocessor RFC Request For Comments A document used as the primary means for communicating information about the TCP IP protocols Some RFCs are designated by the Internet Architecture Board IAB as Internet standards and others are informational RFCs are available online from numerous sources including www rfc editor org RIP Routing Information Protocol An Interior Gateway Protocol IGP supplied with UNIX Berkeley Standard Distribution BSD systems RIP is the most common IGP in the Internet and uses hop count as a routing metric RJ 45 A popular type of cabling connector used for Ethernet cabling It is similar to the RJ 11 connector used for telephone wiring in homes in the United States RJ 45 allows the connection of eight wires ROM Read only memory A type of nonvolatile memory that can be read but not written b
158. igital Network 449 ISDN Channels ISDN includes two types of lines Basic Rate Interface BRI and Primary Rate Interface PRI Both BRI and PRI provide multiple digital bearer channels B channels over which data can be sent and received Because both BRI and PRI have multiple B channels a single BRI or PRI line can have concurrent digital dial circuits to multiple sites Alternately you can create multiple circuits to the same remote site to increase available bandwidth to that site B channels transport data They operate at speeds of up to 64 kbps although the speed might be lower depending on the service provider or might be based on standards in some parts of the world For instance some national standards outside the United States call for 56 kbps B channels ISDN uses another channel inside the same single physical line to ask the telco to set up and tear down circuits The signaling channel called the D channel signals new data calls When a router wants to create a B channel call to another device using a BRI or PRI it sends the phone number that it wants to connect to inside a message sent across the D channel The phone company s switch receives the message and sets up the circuit Signaling a new call over the D channel is effectively the same thing as when you pick up the phone and dial a number to create a voice call The different types of ISDN lines often are descirbed with a phrase that implies the number of each type o
159. igurable value that determines how the router functions during initialization In software the bit position is set by specifying a hexadecimal value using configuration commands console port A component of a router or switch through which commands are entered into a host convergence The time required for routers to react to changes in the network removing bad routes and adding new better routes so that the current best routes are in all the routers routing tables CPE Customer premises equipment Any equipment related to communications that is located at the customer site as opposed to inside the telephone company s network 580 CSMA CD CSMA CD Carrier sense multiple access collision detect A media access mechanism in which devices ready to transmit data first check the channel for a carrier If no carrier is sensed for a specific period of time a device can transmit If two devices transmit at once a collision occurs and is detected by all colliding devices This collision subsequently delays retransmissions from those devices for some random length of time CSU DSU Data service unit channel service unit Used on digital links as an interface to the telephone company in the United States Routers typically use a short cable from a serial interface to a DSU CSU which is attached to the line from the telco with a similar configuration at the other router on the other end of the link demarc The demarcation or separation point betw
160. iguration of IP addresses on the interface Chapter 14 introduces the different IP routing protocols and the CCNA ICND Exam Certification Guide covers the detailed concepts and configuration for several IP routing protocols Routers add routes to their routing tables for the subnets associated with their own physical interfaces To get a better appreciation of this fact examine Example 13 5 which shows several commands from the Seville router Example 13 5 Seville Router Routing Table and Interface Status Commands Seville show ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 E1 OSPF external type 1 E2 OSPF external type 2 E EGP i IS IS L1 IS IS level 1 L2 IS IS level 2 ia IS IS inter area candidate default U per user static route o ODR P periodic downloaded static route Gateway of last resort is not set 10 0 0 0 24 is subnetted 3 subnets c 10 1 3 0 is directly connected EthernetO 07 10 1 130 0 is directly connected Serial 07 10 1 129 0 is directly connected Seriali Seville show ip interface brief Interface IP Address OK Method Status Protocol Serial 10 1 130 253 YES manual up up Serial1 10 1 129 253 YES manual up up Ethernet 10 1 3 253 YES manual up up Yosemite Seville show interface serial 0 Serial is up line protocol is up H
161. in the third octet up to 180 1 254 0 last valid subnet and 180 1 255 0 broadcast subnet 11 Which of the following best describes a feature of CIDR Answer A 12 The phrase to represent hundreds or thousands of client TCP or UDP connections from different hosts as that same number of connections but making it appear as if all connections are from one host best describes which of the following tools Answer C 13 The phrase grouping a large number of Class C networks into a single group and putting a single entry for that group in an Internet router to reduce the overall size of the IP routing table best describes which of the following tools Answer B 14 The phrase the use network 10 0 0 0 in an enterprise network best describes which of the following tools Answer A Q amp A Chapter 12 543 Name the parts of an IP address Answer Network subnet and host are the three parts of an IP address However many people commonly treat the network and subnet parts of an address as a single part leaving only two parts the subnet and host parts On the exam the multiple choice format should provide extra clues as to which terminology is used Define the term subnet mask What do the bits in the mask whose values are binary 0 tell you about the corresponding IP address es Answer A subnet mask defines the number of host bits in an address The bits of value 0 define which bits in the address are
162. in the side of a laptop computer The operating system in the computer still uses the concept of sending data serially but instead of it physically being sent over a cable to an external modem it simply goes to the internal modem card Modem Standards Modems have been around for more than 30 years so as you might imagine a lot of standards have evolved Table 15 3 summarizes some of the modem standards Table 15 3 Modem Standards Standard Speed Comments V 22 1200 bps 600 baud Mainly used outside the United States V 22bis 2400 bps 600 baud First widely deployed worldwide standard V 32 4800 9600 2400 baud Adjusts speed based on line quality V 32bis 14 4kbps 2400 baud Backward compatible with V 32 V 34 28 8 kbps Backward compatible with V 32bis and V 32 V 42 28 8 kbps Same speed as V 34 but with error correction features V 90 56 kbps downstream 33 kbps Created from two earlier competing upstream standards X2 and K56Flex V 92 56 kbps 33 kbps downstream Connects and finds correct speed more upstream or 48 kbps each quickly than V 90 allows modem on direction hold bis simply means version 2 Note that for some standards the speed differs depending on the direction of transmission Most applications today cause a lot more data to be sent toward the client side of the connection For instance when you sit at a PC and browse a web page the web server sends
163. is available 5 What command would you use to receive command help if you knew that a show command option begins with a c but you cannot recall the option Answer show c Help would appear immediately after you typed the symbol You would not need to press Enter after the If you did so the router would try to execute the command with only the parameters that you had typed after the 6 While you are logged in to a router you issue the command copy and get a response of Unknown command computer name or host Offer an explanation for why this error message appears Answer You were in user mode You must be in enable privileged mode to use the copy command When in user mode the router does not provide help for privileged commands and it treats the request for help as if there is no such command 7 Is the number of retrievable commands based on the number of characters in each command or is it simply a number of commands regardless of their size Answer The number of commands The length that is the number of characters of each command does not affect the command history buffer 8 How can you retrieve a previously used command Name two ways Answer Ctrl p and up arrow literally the up arrow key on the keyboard Not all terminal emulators support Ctrl p or the up arrow so recalling both methods is useful 9 After typing show ip route which is the only command that you typed since logging in to the rou
164. is used for receive Compare and contrast the cabling used by an ISDN modem and a cable modem when connecting to the local phone company line or cable drop line Identify the purpose of each pin on the connector Answer ISDN uses a four wire cable using an RJ 45 connector The pinouts pins 3 and 6 for transmit and pins 4 and 5 for receive Cable modems use coaxial cable with a single conductor so there are no pins The round connector on the end of the cable is called an f connector List four standards bodies that have been involved in the development of DSL standards Answer ANSI IEEE ETSI ITU APPENDIX B Decimal to Binary Conversion Table Decimal Value Binary Value Decimal Value Binary Value 0 0000 0000 23 0001 0111 1 0000 0001 24 0001 1000 2 0000 0010 25 0001 1001 3 0000 0011 26 0001 1010 4 0000 0100 27 0001 1011 5 0000 0101 28 0001 1100 6 0000 0110 29 0001 1101 7 0000 0111 30 0001 1110 8 0000 1000 31 0001 1111 9 0000 1001 32 0010 0000 10 0000 1010 33 0010 0001 11 0000 1011 34 0010 0010 12 0000 1100 35 0010 0011 13 0000 1101 36 0010 0100 14 0000 1110 37 0010 0101 15 0000 1111 38 0010 0110 16 0001 0000 39 0010 0111 17 0001 0001 40 0010 1000 18 0001 0010 41 0010 1001 19 0001 0011 42 0010 1010 20 0001 0100 43 0010 1011 21 0001 0101 44 0010 1100 22 0001 0110 45 0010 1101 continues 566 Appendix B Decimal to Binary Conv
165. k media Name three benefits to layering networking protocol specifications Answer Some examples of benefits to layering networking protocol specifications include reduced complexity standardized interfaces modular engineering interoperable technology accelerated evolution and simplified teaching and learning Questions such as this on the exam require some subjective interpretation of the wording on your part What header or trailer does a router discard as a side effect of routing Answer A router discards the data link header and trailer as a side effect of routing This is because the network layer where routing is defined is interested in delivering the network layer Layer 3 PDU from end to end Routing uses intermediate data links 502 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 12 13 14 15 16 17 Layer 2 to transport the data to the next routers and eventually to the true destination The data link header and trailer are useful only to deliver the data to the next router or host so the header and trailer are discarded by each router What OSI layer typically encapsulates using both a header and a trailer Answer The data link layer typically encapsulates using both a header and a trailer The trailer typically includes a frame check sequence FCS which is used to perform error detection What terms are used to describe the contents of the data encapsula
166. ks would allow a Class B network to allow subnets to have up to 150 hosts and allow for up to 164 subnets Answer C You need 8 bits to number up to 150 hosts because 27 2 is less than 150 but 28 2 is greater than 150 Similarly you need 8 subnet bits The only valid Class B subnet mask with 8 host and 8 subnet bits is 255 255 255 0 Which of the following subnet masks would allow a Class A network to allow subnets to have up to 150 hosts and would allow for up to 164 subnets Answer B You need 8 host bits and 8 subnet bits Because the mask is used with a class A network any mask with the entire second octet as part of the subnet field and with the entire fourth octet as part of the host field meets the requirement 542 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 9 Which of the following are valid subnet numbers in network 180 1 0 0 when using mask 255 255 248 0 Answer C D E and F In this case the subnet numbers begin with 180 1 0 0 subnet zero and then 180 1 8 0 180 1 16 0 180 1 24 0 and so on increasing by 8 in the third octet up to 180 1 240 0 last valid subnet and 180 1 248 0 broadcast subnet 10 Which of the following are valid subnet numbers in network 180 1 0 0 when using mask 255 255 255 0 Answer A B C D E and F In this case the subnet numbers begin with 180 1 0 0 subnet zero and then 180 1 1 0 180 1 2 0 180 1 3 0 and so on increasing by 1
167. l designed for use within a single organization For example an entire company might choose the IGRP routing protocol which is an interior routing protocol Distance vector The logic behind the behavior of some interior routing protocols such as RIP and IGRP Link state The logic behind the behavior of some interior routing protocols such as OSPF Balanced hybrid The logic behind the behavior of EIGRP which is more like distance vector than link state but is different from these other two types of routing protocols Dijkstra Shortest Path First SPF algorithm Magic math used by link state protocols such as OSPF when the routing table is calculated Diffusing Update Algorithm DUAL The process by which EIGRP routers collectively calculate the routes to place into the routing tables Convergence The time required for routers to react to changes in the network removing bad routes and adding new better routes so that the current best routes are in all the routers routing tables Metric The numeric value that describes how good a particular route is The lower the value is the better the route is 422 Chapter 14 Introduction to Dynamic Routing Protocols Foundation Summary The Foundation Summary section of each chapter lists the most important facts from the chapter Although this section does not list every fact from the chapter that will be on your CCNA exam a wel
168. l prepared CCNA candidate should know at a minimum all the details in each Foundation Summary section before going to take the exam All routing protocols have several general goals as summarized in the following list m To dynamically learn and fill the routing table with a route to all subnets in the network m If more than one route to a subnet is available to place the best route in the routing table m To notice when routes in the table are no longer valid and to remove those routes from the routing table m Ifa route is removed from the routing table and another route through another neighboring router is available to add the route to the routing table Many people view this goal and the preceding one as a single goal m To add new routes or to replace lost routes with the best currently available route as quickly as possible The time between losing the route and finding a working replacement route is called convergence time m To prevent routing loops The following list summarizes a few very important terms related to routing and routing protocols m A routing protocol fills the routing table with routing information Examples include RIP and IGRP m A routed protocol is a protocol with OSI Layer 3 characteristics that define logical addressing and routing The packets defined by the network layer Layer 3 portion of these protocols can be routed Examples of protocols include IP and IPX m The term routing ty
169. lco Even when the routers have no data to send the full bandwidth is available to be used 508 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 7 True or False Frame Relay VCs provide a constant amount of bandwidth between two devices typically routers never more and never less Defend your answer Answer False The provider assigns a guaranteed bandwidth or CIR for a VC but the routers on either end of the VC can send more than the CIR of data As long as the service provider has enough capacity to support it the frames are forwarded over the VC 8 Explain how many DSO channels fit into a T1 and why the total does not add up to the purported speed of a T1 which is 1 544 Mbps Answer Each DSO channel runs at 64 kbps With 24 in a T1 the T1 speed seemingly would be 24 64 kbps or 1 536 Mbps T1 also includes 8 kbps for management which when added to the 1 536 Mbps total gives you the full T1 rate 1 544 Mbps 9 Define the term synchronous Answer The imposition of time ordering on a bit stream Practically a device will try to use the same speed as another device on the other end of a serial link By examining transitions between voltage states on the link the device can notice slight variations in the speed on each end and can adjust its speed accordingly 10 Imagine a drawing with two routers each connected to an external CSU DSU which each is connected with a fo
170. le Examples 13 2 13 3 and 13 4 show the IP configuration details for the three routers in Figure 13 1 The full configuration for Albuquerque is shown in Example 13 2 with a briefer version of the configs of the other two routers in Examples 13 3 and 13 4 Example 13 2 Albuquerque Router Configuration and Exec Commands Albuquerque configure terminal Enter configuration commands one per line End with CNTL Z Albuquerque config interface serial 0 Albuquerque config if ip address 10 1 128 251 255 255 255 0 Albuquerque config interface serial 1 Albuquerque config if ip address 10 1 130 251 255 255 255 0 Albuquerque config interface ethernet 0 Albuquerque config if ip address 10 1 1 251 255 255 255 0 Configuring IP Addresses 373 Example 13 2 Albuquerque Router Configuration and Exec Commands Continued Albuquerque show running config Building configuration Current configuration 872 bytes version 12 2 service timestamps debug uptime service timestamps log uptime no service password encryption hostname Albuquerque I enable secret 5 1 J3Fz QaEYNIiI2aMu 3Ar q0Xm ip name server 10 1 1 100 ip name server 10 1 2 100 interface Seriald ip address 10 1 128 251 255 255 255 0 interface Seriali ip address 10 1 130 251 255 255 255 0 interface Ethernet ip address 10 1 1 251 255 255 255 0 i no ip http server banner motd C line con password cisco login line aux 0 line vty 4
171. ler The trailer typically includes a frame check sequence FCS which is used to perform error detection 10 11 12 13 14 15 16 Chapter3 505 If a Fast Ethernet NIC currently is receiving a frame can it begin sending a frame Answer Yes if the NIC is operating in full duplex mode What are the two key differences between a 10 Mbps NIC and a 10 100 NIC Answer The obvious benefit is that the 10 100 NIC can run at 100 Mbps The other benefit is that 10 100 NICs can autonegotiate both speed and duplex between itself and the device that it is cabled to typically a LAN switch What is the distance limitation of a single cable for 1OBASE T For 100 BASE TX Answer 10BASE T allows 100 m between the device and the hub or switch as does 100 BASE TX How fast is Fast Ethernet Answer 100 million bits per second 100 Mbps How many bytes long is a MAC address Answer 6 bytes long or 48 bits Define the difference between broadcast and multicast MAC addresses Answer Both identify more than one device on the LAN Broadcast always implies all devices on the LAN whereas multicast implies some subset of all devices Multicast is not allowed on Token Ring broadcast is allowed on all LAN types Devices that intend to receive frames addressed to a particular multicast address must be aware of the particular multicast address es that they should process These addresses are dependent on the applications us
172. ll mesh for a particular set of networking devices a direct cable connects each pair of devices For a partial mesh some pairs of devices are not directly connected 3 Compare and contrast full mesh versus partial mesh topologies in relation to logical topologies Answer Regardless of the physical topology a topology is considered a logical full mesh if each pair of devices can communicate directly and is considered a partial mesh if some pairs cannot communicate directly A Frame Relay network uses a star physical topology Depending on what VCs have been defined it might use a logical full mesh or a logical partial mesh 4 What is the main motivation for using a dual ring physical topology versus a single ring Why Answer For better network availability With dual rings if a cable or a device fails the devices near the failure can loop the signals from the two different cables together thereby creating a single phyiscal path that loops to each node 10 11 Chapter11 539 What two methods are used to reduce the amount of electromagnetic emissions emanating from copper Ethernet cabling Why do they help reduce emissions Answer By using two pairs of wires for transmission with differing currents and twisting the wires the magnetic fields generated when the electrical current flows are cancelled The other method is to put insulating material around the wires which shields the emissions to a great degree
173. llowed by the notation of 24 This notation called prefix notation denotes the subnet mask in terms of the number of 1 bits in the subnet mask The number of bits of value binary 1 in the mask is considered to be the prefix For instance mask 255 255 255 0 used in the examples translates to a prefix of 24 because 255 255 255 0 has 24 binary 1s Prefix notation is simply a shorter way to write the mask If you prefer to see the subnet masks instead of the prefix simply use the terminal ip netmask format decimal exec command as shown at the end of Example 13 2 Note that the show ip route command issued after the terminal command shows the subnet mask instead of the prefix Seeding the Routing Table with Connected IP Routes The Cisco IOS routes IP packets by default in other words you do not need to type any commands to tell the router to enable IP routing Before the router will route packets in or out an interface the interface must have an IP address as shown in the earlier examples So as configured each of the three routers can route packets on three different interfaces 376 Chapter 13 Basic Router Configuration and Operation The problem with the configurations shown so far is that the routers do not know routes to all the subnets in the network The ultimate solution to this problem is to configure a dynamic routing protocol However in this chapter you will learn about how the router learns some routes by virtue of the conf
174. lnetted from Foundation Summary 399 CDP discovers several useful details from neighboring networking devices including the following You also should review the actual CDP commands in the chapter and memorize which commands provide which details Device identifier Typically the host name Address list Network and data link addresses Port identifier Text that identifies the port which is another name for an interface Capabilities list Information on what type of device it is for instance a router or a switch Platform The model and OS level running in the device 400 Chapter 13 Basic Router Configuration and Operation O amp A As mentioned in the introduction you have two choices for review questions The questions that follow give you a bigger challenge than the exam itself by using an open ended question format By reviewing now with this more difficult question format you can exercise your memory better and prove your conceptual and factual knowledge of this chapter The answers to these questions are found in Appendix A For more practice with exam like question formats including questions using a router simulator and multiple choice questions use the exam engine on the CD Create a minimal configuration enabling IP on each interface on a 2501 router two serial one Ethernet The NIC assigned you network 8 0 0 0 Your boss says that you need at most 200 hosts per subnet You decide against using VLS
175. ls work well but RIP 2 is more functional If you want a routing protocol that uses a public standard and you want to avoid the complexity of link state protocols RIP 2 is your best choice Interior Gateway Routing Protocol IGRP is a Cisco proprietary IP routing protocol created by Cisco more than 10 years ago Cisco created IGRP to provide a better distance vector protocol to its customers as compared with RIP 1 Routing Protocol Overview 415 The most obvious difference between RIP 1 and IGRP is the metric IGRP advertises up to five parameters that describe the metric for each route although practically only two ever are used bandwidth and delay The bandwidth part of this more complex metric describes the constrained link speed For instance if a route to a subnet contained all Fast Ethernet links the bandwidth in the update would be 100 Mbps however if a single 56 kbps link were in the path the bandwidth would be listed as 56 kbps The delay component includes a cumulative number for instance a route going over ten Fast Ethernet links would have its delay part of the metric ten times bigger than a route with a single 100 Mbps link in the path IGRP calculates the metric based on a mathematical formula that you do not really need to know for the exam The formula uses bandwidth and delay as input and results in an integer value the metric between 1 and 4 294 967 295 Figure 14 4 shows the benefit of this better metric Figu
176. more cumulative bandwidth Multiple 10 or 100 Mbps Ethernet segments are created and unicasts between devices on the same segment are not forwarded by the bridge which reduces overhead Because frames can be sent over each segment at the same time it increases the overall bandwidth available in the network What routing protocol does a transparent bridge use to learn about Layer 3 addressing groupings Answer None Bridges do not use routing protocols Transparent bridges do not care about Layer 3 address groupings Devices on either side of a transparent bridge are in the same Layer 3 group in other words the same IP subnet or IPX network 10 11 Chapter9 531 If a Fast Ethernet NIC currently is receiving a frame can it begin sending a frame Answer Yes if the NIC is operating in full duplex mode Why did Ethernet networks performance improve with the advent of bridges Answer Before bridges and switches existed all devices were cabled to the same shared Ethernet The CSMA CD algorithm was used to determine who got to send across the Ethernet As the amount of traffic increased collisions and waiting because CSMA CD increased so frames took longer to send Bridges separated the network into multiple collision domains reducing collisions and allowing devices on opposite sides of the bridge to send concurrently Why did Ethernet networks performance improve with the advent of switches Answer Before bridge
177. mputer system on a network Similar to a node except that host usually implies a computer system whereas node generally applies to any networked system including access servers and routers HTML Hypertext Markup Language A simple hypertext document formatting language that uses tags to indicate how a given part of a document should be interpreted by a viewing application such as a web browser HTTP Hypertext Transfer Protocol The protocol used by web browsers and web servers to transfer files such as text and graphic files ICMP Internet Control Message Protocol A network layer Internet protocol that reports errors and provides other information relevant to IP packet processing Documented in RFC 792 TEEE 802 2 An JEEE LAN protocol that specifies an implementation of the LLC sublayer of the data link layer IEEE 802 2 handles errors framing flow control and the network layer Layer 3 service interface Used in IEEE 802 3 and IEEE 802 5 LANs TEEE 802 3 An IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sublayer of the data link layer IEEE 802 3 uses CSMA CD access at a variety of speeds over a variety of physical media TEEE Institute of Electrical and Electronics Engineers A professional organization that develops communications and network standards among other activities IGRP Interior Gateway Routing Protocol Interior Gateway Protocol IGP developed by Cisco to address the issues asso
178. n Layer 7 presentation Layer 6 session Layer 5 transport Layer 4 network Layer 3 data link Layer 2 and physical Layer 1 Some mnemonics to help you recall the names of the layers are All People Seem To Need Data Processing Layers 7 to 1 Please Do Not Take Sausage Pizzas Away Layers 1 to 7 and the ever popular Pew Dead Ninja Turtles Smell Particularly Awful Layers 1 to 7 2 What is the main purpose s of Layer 7 Answer Layer 7 the application layer provides standardized services to applications The definition for this layer is typically ambiguous because it varies The key is that it does not define a user interface but instead it is a sort of toolbox used by application developers For example a web browser is an application that uses HTTP as defined as a TCP IP application layer protocol to transfer the contents of web page between a server and client 3 What is the main purpose s of Layer 6 Answer Layer 6 the presentation layer defines data formats compression and possibly encryption 4 What is the main purpose s of Layer 5 Answer Layer 5 the session layer controls the conversation between two endpoints Although the term used is session the term conversation more accurately describes what is accomplished The session layer ensures that not only communication but also useful sets of communication between endpoints is accomplished 10 11 Chapter2 501 What is the main purpose s
179. n exe that is on the CD s root directory After logging in select the Hands on Practice Exercises and NetSim Demo Software link in the main menu Another menu opens that allows you to view the CD only appendixes of labs and to start the NetSim software NetSim lets you pick which lab topology to load You pick a lab topology and you next see the NetSim user interface You can think of what you see next as a real lab with real routers and switches The cabling topology and interface numbers match the labs and scenarios in this book So you can access the devices and start entering commands The NetSim software includes the NetSim user guide which helps you figure out how to navigate and use the NetSim product Just select help and User guide from NetSim However the user manual does not tell you anything about the hands on exercises you can do with this special version of NetSim You can always just experiment using NetSim trying all the commands you can think of but remember that this is a limited use version of the software so not all commands are enabled If you want some instructions on good things to try to do with the simulator read the next section It lists all the labs and scenarios in this book that can be performed using NetSim Hands on Exercises Available with NetSim This book includes two main types of exercises that can be duplicated using real gear or the special NetSim network simulator scenarios and lab
180. n the ISDN term B channel a b c d Bearer Broadband Binary Best Which of the following DSL standards has a limit of 18 000 feet for the length of the local loop a b c d e IDSL DSL ADSL VDSL HDSL Imagine a local phone line from a house to a local telco CO When the customer at that house requests DSL service what type of device does the telco move the CO end of the local line to a b DSLAM DSL router DSL modem Class 5 switch Voice switch Head end Do I Know This Already Quiz 433 10 Which of the following protocols are used by DSL modem and routers for data link layer functions a b c d e PPP IEFE 802 3 ATM IEFE 802 1Q MCNS MAC 11 Which of the following protocols is used by cable modems for data link layer functions PPP IEEE 802 3 ATM IEEE 802 1Q MCNS MAC 12 Which of the following protocols are used by a cable modem for the upstream data PCM QAM 16 QAM 64 QAM 256 QPSK 13 Which of the following remote access technologies uses ATM Ethernet and PPP as data link protocols a b c Analog modems ISDN DSL Cable modems 434 Chapter 15 Remote Access Technologies 14 Which of the following remote access technologies support specifications that allow both symmetric speeds and asymmetric speeds a b c d Analog modems ISDN DSL Cable modems 15 Which of the following remote access technologies when used to conn
181. nable secret 5 1 J3Fz QaEYNIiI2aMu 3Ar qQXm ip subnet zero no ip domain lookup interface Serial ip address 163 1 13 203 255 255 255 128 no fair queue interface Serial1 ip address 163 1 23 203 255 255 255 128 encapsulation ppp interface Ethernet ip address 163 1 3 203 255 255 255 128 router rip continues 492 Chapter 16 Final Preparation Example 16 7 Part C R3 show and debug Output Continued network 163 1 0 0 ip classless no ip http server I I line con 0 password cisco login line aux 0 line vty 4 password cisco login I end R3 show ip arp N1 OSPF NSSA external type 1 N2 i IS IS L1 IS IS level 1 L2 candidate default U per user static route o P periodic downloaded static route Gateway of last resort is not set 163 1 0 0 16 is variably subnetted 7 subnets 2 masks R3 trace 163 1 13 203 Type escape sequence to abort E1 OSPF external type 1 E2 OSPF external type 2 IS IS level 2 ia ODR Protocol Address Age min Hardware Addr Type Interface Internet 163 1 3 203 Q000 0c89 b1b0 SNAP EthernetO R3 show ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area OSPF NSSA external type 2 E EGP IS IS inter area R 163 1 2 128 25 120 1 via 163 1 23 202 00 00 22 Serial1 c 163 1 3 128 25 is directly connected Ether
182. namic Routing Protocols OSPF uses a concept called cost for the metric Each link is considered to have a cost a route s cost is the sum of the cost for each link By default Cisco derives the cost value for a link from the bandwidth so you can think of the metric as being based on cumulative link bandwidth IGRP s metric is based on delay and bandwidth but it does not treat bandwidth as a cumulative value it considers only the slowest link in a path The following list points out some of the key features of OSPF m Converges very quickly from the point of recognizing a failure it often can converge in less than 10 seconds m Supports VLSM m Uses short Hello messages on a short regular interval the Hello interval with the absence of Hello messages indicating that a neighbor is no longer reachable m Sends partial updates when link status changes and floods full updates every 30 minutes The flooding however does not happen all at once so the overhead is minimal m Uses cost for the metric Integrated IS IS Once upon a time the world of networking consisted of proprietary networking protocols from the various computer vendors For companies that bought computers from only that one vendor there was no problem However when you used multiple vendor s computers networking became more problematic One solution to the problem was the development of a standardized networking protocol such as TCP IP Skipping a few d
183. native routes that could be used if the current route fails An alternative route using what DUAL calls a feasible successor route is guaranteed to be loop free So if the current best route fails the router immediately can start using the feasible successor route instead so that convergence can happen very quickly 420 Chapter 14 Introduction to Dynamic Routing Protocols The following list points out some of the key similarities to some of the other protocols covered in this introduction m Like OSPF and Integrated IS IS it converges quickly often in less than 3 seconds after a failure is recognized m Like OSPF EIGRP discovers neighbors before sending them routing information m Like RIP andIGRP EIGRP requires very little design effort Link state protocols require some design work in medium to larger networks m Like IGRP EIGRP is Cisco proprietary m Like IGRP EIGRP uses a metric based on bandwidth and delay EIGRP uses the same metric as IGRP except that EIGRP scales the metric by multiplying by 256 m Like link state protocols EIGRP does not send full updates on a periodic interval but rather sends partial updates only as links or routers go up and down m Like link state protocols EIGRP builds some topology tables in addition to the IP routing table Summary of Interior Routing Protocols Before finishing your study for the ICND or CCNA exam you will learn a lot more about RIP 1 IGRP EIGRP and OSPF This chapter h
184. ned to determine the interface out which to forward the frame Table lookup is required for both addresses for any frame that enters an interface That is one of the reasons that LAN switches which have a much larger number of interfaces than traditional bridges need to have optimized hardware and logic to perform table lookup quickly 16 Define the term broadcast domain Answer A broadcast domain is a set of Ethernet devices for which a broadcast sent by any one of them should be received by all others in the group Unlike routers bridges and switches do not stop the flow of broadcasts Two segments separated by a router each would be in different broadcast domains A switch can create multiple broadcast domains by creating multiple VLANs but a router must be used to route packets between the VLANs 17 18 19 20 Chapter9 533 Describe the benefits of creating 3 VLANs of 25 ports each versus a single VLAN of 75 ports in each case using a single switch Assume that all ports are switched ports each port is a different collision domain Answer Three different broadcast domains are created with three VLANs so the devices CPU utilization should decrease because of decreased broadcast traffic Traffic between devices in different VLANs will pass through some routing function which can add some latency for those packets Better management and control are gained by including a router in the path for those packets Ex
185. needed for the network in Figure 13 3 Table 13 5 ICMP Unreachable Codes What It Typically Is bit set and a router must fragment to forward the packet Unreachable Code When It Is Used Sent By Network unreachable There is no match ina routing table Router for the packet s destination Host unreachable The packet can be routed to a Router router connected to the destination subnet but the host is not responding Can t fragment The packet has the Don t Fragment Router continues 386 Chapter 13 Basic Router Configuration and Operation Table 13 5 ICMP Unreachable Codes Continued What It Typically Is Unreachable Code When It Is Used Sent By Protocol unreachable The packet is delivered to the Endpoint host destination host but the transport layer protocol is not available on that host Port unreachable The packet is delivered to the Endpoint host destination host but the destination port has not been opened by an application The following list explains each code in Table 8 8 in greater detail using the network in Figure 13 3 as an example m Network unreachable Router A uses this code if it does not have a route telling it where to forward the packet In this case Router A needs a route to subnet 10 1 2 0 Router A sends Fred the ICMP Destination Unreachable message with the code network unreachable in response to Fred s packet destined for 10 1 2 14
186. nel used for data this is called out of band signaling Integrated Services Digital Network 451 Typical Uses of ISDN Routers frequently use ISDN to create a backup link when their primary leased line or Frame Relay connection is lost Although the leased line or Frame Relay access link seldom fails when it does a remote site might be completely cut off from the rest of the network Depending on the business goals of the network long outages might not be acceptable so ISDN could be used to dial back to the main site The ICND exam covers ISDN as well including the features and configuration used by routers The scenarios in Figure 15 10 show some of the typical situations in which ISDN can be used described as follows m Case 1 shows dial on demand routing DDR Logic is configured in the routers to trigger the dial when the user sends traffic that needs to get to another site m Case 2 shows a typical telecommuting environment m Case 3 shows a typical dial backup topology The leased line fails so an ISDN call is established between the same two routers m Case 4 shows where an ISDN BRI can be used to dial directly to another router to replace a Frame Relay access link or a failed virtual circuit VC Figure 15 10 Typical Occasional Connections Between Routers OES e 4 E BoD Leased Line a Ze Le J Z _ I ISDN Frame Relay eS X Te o ses _ Ps ISDN PRIs allow for larger scale ISDN be
187. net R 163 1 1 128 25 120 1 via 163 1 13 201 00 00 28 Seriald R 163 1 12 128 25 120 1 via 163 1 13 201 00 00 28 Seriald 120 1 via 163 1 23 202 00 00 22 Seriali c 163 1 13 128 25 is directly connected Serial Cc 163 1 23 128 25 is directly connected Seriali c 163 1 23 202 32 is directly connected Seriali Scenario Part A Planning 493 Example 16 7 Part C R3 show and debug Output Continued Tracing the route to 163 1 13 203 1 163 1 13 201 16 msec 16 msec 16 msec 2 163 1 13 203 44 msec 32 msec R3 ping 163 1 13 203 Type escape sequence to abort Sending 5 10 byte ICMP Echos to 163 1 13 203 timeout is 2 seconds Success rate is 100 percent 5 5 round trip min avg max 64 66 68 ms Answer the following questions Use Examples 16 5 16 6 and 16 7 as references 1 What command tells you the contents of the ARP cache 2 What command is used to find the path a packet would take from R3 to 163 1 1 1 3 Imagine that R3 s EO interface needs to use a new IP address and mask 10 1 1 1 255 255 255 0 If the user is in user mode what steps are necessary to change the IP address 4 If an exec command that you cannot recall begins with the letter C how can you get Help to list all commands that start with C List the steps assuming that you are in privileged mode 5 Name the two commands to list the currently used configuration in a router 6 Name the two commands to list the configuration t
188. nswer write terminal and show running config show running config is the newer command and hopefully is easier to remember 31 True or false The copy startup config running config command always changes the currently used configuration for this router to exactly match what is in the startup configuration file Explain Answer False Some configuration commands do not replace an existing command but simply are added to a list of related commands If such a list exists the copy startup config running config command simply adds those to the end of the list Many of these lists in a router configuration are order dependent Chapter 8 Do Know This Already Quiz 1 In which of the following modes of the CLI could you configure the duplex setting for interface fastethernet 0 5 Answer E The duplex command is an interface subcommand Q amp A Chapter8 525 In which of the following modes of the CLI could you issue a command to erase the initial configuration of the switch Answer B The erase command is an exec command so it cannot be issued from any configuration mode User mode does not allow the use of the erase command What type of switch memory is used to store the configuration used by the switch when the switch first comes up Answer D IOS loads the config from NVRAM into RAM during the boot sequence What command copies the configuration from RAM into NVRAM Answer F The first parameter identifies
189. ntegrated Services Digital Network Integrated Services Digital Network ISDN provides switched dialed digital WAN services in increments of 64 kbps Before ISDN the only widely available method to dial a circuit for data communication between two computers was to use analog modems When ISDN was created analog modem speeds typically did not even exceed 9600 bps The phone companies of the world wanted to have a dialed service that not only allowed faster transmission rates but also was pervasive as a simple analog line used for voice Today one could argue that the collective phone companies of the world were ultimately successful with this goal but not totally successful ISDN is widely available It is still a popular technology for dial backup between business sites when a point to point or Frame Relay link fails ISDN was created more than 20 years ago and it began being widely deployed in the United States by the early 1990s However competing technologies such as DSL and cable have usurped ISDN in the marketplace for home access to ISPs However ISDN remains a popular choice for dial backup 448 Chapter 15 Remote Access Technologies ISDN requires that the two endpoint computers have the ISDN equivalent of an analog modem There are many variations of these ISDN devices mainly as a result of the fact that ISDN was created as a worldwide standard so many options were needed to meet the differing needs of the telcos in different par
190. o not include the mask in the routing updates Explain the difference between interior and exterior routing protocols Answer Interior routing protocols are designed to advertise detailed routing information about each subnet typically inside a single company or organization Exterior routing protocols are designed to advertise information about how to reach different organizations networks through the Internet and they purposefully try to reduce the detailed routing information to reduce the number of routes in Internet routers routing tables Explain the difference between full and partial routing updates Answer Full routing updates include information about each subnet during each update interval Partial updates just include changed routes such as newly learned subnets and subnets whose routes have failed Define the term balanced hybrid in relation to the terms distance vector and link state Answer Balanced hybrid is a term used to refer to the logic used by EIGRP The logic can be viewed as a combination of features like those of distance vector protocols and link state protocols Compare and contrast the types of information sent in distance vector routing updates versus link state routing updates Answer Distance vector routing updates contain a subnet number and a metric for each route Link state updates define much more detailed information such as the identity of each router and which subnets each router is conne
191. of administratively down and down The show ip interfaces and show interfaces commands would show the same status for serial 1 At the end of the example the no shutdown command brings the interface back up 380 Chapter 13 Basic Router Configuration and Operation Bandwidth Clock Rate and Serial Lines in the Lab As mentioned back in Chapter 4 Fundamentals of WANs you can build a WAN link in a lab without using a CSU DSU The lab network that I used to build the examples in this chapter used three back to back serial cables essentially a DTE and DCE cable pair connected together To use a back to back WAN connection one router must supply the clocking Example 13 7 shows an example configuration for Seville with a couple of important commands related to WAN links Example 13 7 Seville Router Configuration with clock rate Command Seville show running config Lines ommitted for brevity interface Seriald ip address 10 1 130 253 255 255 255 0 clock rate 128000 interface Seriali ip address 10 1 129 253 255 255 255 0 clock rate 128000 bandwidth 128 Etherneto ip address 10 1 3 253 255 255 255 0 I Lines ommitted for brevity Seville show controllers serial 0 0 Interface Serial Hardware is PowerQUICC MPC860 DCE V 35 clock rate 128000 idb at 0x8169BB20 driver data structure at 0x816A35E4 Lines ommitted for brevity The clock rate command sets the rate in bits per second on the router tha
192. of forwarding packets You might even want to review the section IP Routing and Routing Protocols in Chapter 5 Fundamentals of IP for a review of routing before proceeding with this chapter For those of you studying for the CCNA exam if you are following the reading plan outlined in the introduction you will move to the CCNA ICND Exam Certification Guide after this chapter For those of you studying just for the INTRO exam this chapter completes the coverage of topics related to IP and IP routing Do I Know This Already Quiz The purpose of the Do I Know This Already quiz is to help you decide whether you really need to read the entire chapter If you already intend to read the entire chapter you do not necessarily need to answer these questions now The eight question quiz derived from the major sections in the Foundation Topics portion of the chapter helps you determine how to spend your limited study time Table 14 1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions that correspond to those topics 404 Chapter 14 Introduction to Dynamic Routing Protocols Table 14 1 Do I Know This Already Foundation Topics Section to Question Mapping Foundations Topics Section Questions Covered in This Section Routing Protocol Overview 1 8 CAUTION The goal of self assessment is to gauge your mastery of the topics in this chapte
193. ogin command which follows the line console 0 command tells IOS that a password prompt is desired at the console What configuration command is used to tell the router the password that is required at the console What configuration mode context must you be in That is what command s must you type before this command after entering configuration mode List the commands in the order in which they must be typed while in config mode line console password XXXXXXX Answer The password command tells IOS the value that should be typed when a user wants access from the console This value is requested by IOS because of the login command The password xxxxxxx must be typed while in console configuration mode which is reached by typing line console 0 What are the primary purposes of Flash memory in a Cisco router Answer To store IOS and microcode files In most routers only IOS is stored in flash If microcode is upgraded the files also reside in Flash memory What is the intended purpose of NVRAM memory in a Cisco router Answer To store a single configuration file used at router load time NVRAM does not support multiple files 522 Appendix A Answers to the Do I Know This Already Quizzes and O amp A Sections 15 What does the NV stand for in NVRAM Answer Nonvolatile NVRAM is battery powered if it is really RAM In some routers Cisco has sneakily used a small portion of Flash memory for the purpose of NVRAM but Cisco
194. ommand it sets the console password under line vty 0 4 it sets the telnet password The enable password can be set with the enable password or enable secret commands with the enable secret password taking precedence if both are configured 10 Chapter 13 553 In the output of show ip route when a C shows up in the left side of the output on a line for a particular route what does that mean Answer C means connected This means that the route was learned by this router because it has an operational interface that is connected directly to that subnet Define the term prefix notation Give two examples Answer The representation of a subnet mask with a slash character followed by a number that represents the number of binary 1s in the mask For example 16 means the same thing as 255 255 0 0 and 22 means the same thing as 255 255 252 0 What does ICMP stand for To which OSI layer would you consider this protocol to apply most closely Answer Internet Control Message Protocol ICMP is considered a Layer 3 protocol because it is used for control and management of IP Identify two methods to tell a router to ask for name resolution from two different name servers ip name server 1 1 1 1 2 2 2 2 or ip name server 1 1 1 1 ip name server 2 2 2 2 Answer Both methods tell the router to first try the name server at 1 1 1 1 and then try the name server at 2 2 2 2 What keyboard sequence suspends a Telnet session in
195. ompany called Boson Software Inc www boson com produces a network simulation product called NetSim The full NetSim product available over the Internet from Boson contains a large number of lab exercises and support for a large number of devices You can even design your own network topology from scratch It is a very impressive product The CD included with this book has a version of NetSim built specifically for this book This version of NetSim includes support for several lab exercises and lab scenarios that were written just for this book Although the software lets you work through these exercises it is a limited feature demo version of the actual NetSim software which requires paid registration for full functionality The full feature version of NetSim includes a large set of other labs including labs appropriate for the CCNP exams You can also build a network topology with the full version of the product so you can try any of the examples in this book or to experiment with networks This short appendix explains the following How to get to the NetSim user interface on the CD m What hands on exercises in the book can be performed using this special edition of NetSim 572 Appendix C Using the Simulation Software for the Hands on Exercises Accessing NetSim from the CD Accessing NetSim from the CD is relatively simple Put the CD in the CD drive and the software on the CD starts If it doesn t run the command autoru
196. or HDLC Answer E 5 Which of the following WAN data link protocols on Cisco routers support multiple Layer 3 protocols by virtue of having some form of Protocol Type field Answer A B and C 6 Ona point to point WAN link between two routers what device s are considered to be the DTE devices Answer A 7 Imagine that Router1 has three point to point serial links one link each to three remote routers Which of the following is true about the required HDLC addressing at Router1 Answer E 8 What is the name of the Frame Relay field used to identify Frame Relay Virtual Circuits Answer A 9 Which of the following is true about Frame Relay virtual circuits Answer B 10 Which of the following defines a SONET link speed around 155 Mbps Answer E Q amp A Chapter 4 507 Are DLCI addresses defined by a Layer 2 or Layer 3 protocol Answer DLCI addresses are defined by a Layer 2 protocol Although they are not covered specifically in this chapter Frame Relay protocols do not define a logical addressing structure that can usefully exist outside a Frame Relay network by definition the addresses would be OSI Layer 2 equivalent What OSI layer typically encapsulates using both a header and a trailer Answer The data link layer typically encapsulates using both a header and a trailer The trailer typically includes a frame check sequence FCS which is used to perform error detection Define the terms DCE and DT
197. or instance a point to point serial link needs only two IP addresses so a subnet mask of 255 255 255 252 which allows only two valid IP addresses meets the requirements but does not waste IP addresses A mask allowing a much larger number of IP addresses then can be used on each LAN based subnet Some routing protocols support VLSM and some do not Classless or classful Classless routing protocols transmit the subnet mask along with each route in the routing updates sent by that protocol Classful routing protocols do not transmit mask information So only classful routing protocols support VLSM To say that a routing protocol is classless is to say that it supports VLSM and vice versa 410 Chapter 14 Introduction to Dynamic Routing Protocols The next few sections take you through the basics of each of the types of interior routing protocols as well as give you a short description of each routing protocol Routing Through the Internet with the Border Gateway Protocol ISPs use BGP today to exchange routing information between themselves and other ISPs and customers Whereas interior routing protocols might be concerned about advertising all subnets inside a single organization with a large network having a few thousand routes in the IP routing table exterior routing protocols try to make sure that advertising routes reach every organization s network Exterior routing protocols also deal with routing tables that with
198. osts A traceroute protocol also is defined in RFC 1393 transparent bridge A device that forwards frames between LAN segments based on the destination MAC address Transparent bridging is so named because the presence of bridges is transparent to network end nodes trunking Also called VLAN trunking A method using either Cisco s ISL protocol or the IEEE 802 1q protocol to support multiple VLANs that have members on more than one switch twisted pair Transmission medium consisting of two insulated wires arranged in a regular spiral pattern The wires can be shielded or unshielded Twisted pair is common in telephony applications and in data networks UDP User Datagram Protocol Connectionless transport layer protocol in the TCP IP protocol stack UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery update timer A timer used by a router to indicate when to send the next routing update user mode A mode of the user interface to a router or switch in which the user can type only nondisruptive EXEC commands generally just to look at the current status but not to change any operational settings 590 UTP UTP Unshielded twisted pair A four pair wire medium used in a variety of networks UTP does not require the fixed spacing between connections that is necessary with coaxial type connections Five types of UTP cabling are commonly used Category 1 through Category 5 cabling VLAN A group of
199. ous when you are changing the configuration or using potentially damaging exec commands be careful about what router you are actually using when you have suspended Telnet connections If you want to know which session has been suspended most recently look for the session listed in the show session command that has an asterisk to the left of the entry That session was the most recently suspended session 392 Chapter 13 Basic Router Configuration and Operation Table 13 8 summarizes the commands related to Telnet Table 13 8 Telnet Command Options Function Command Options Telnet to another device Use the telnet exec command Just type the host name or IP address from exec mode Suspend a Telnet session Press the key sequence Ctrl Shift 6 then x Discover currently suspended Telnet session Use the where exec command Use the show sessions exec command Resume a suspended Telnet session Use the resume command with no parameter to reconnect to the most recently suspended Telnet Use the resume x command where x is the number of the suspended Telnet session based on the output of show sessions Just press Enter in exec mode to resume to the most recently suspended Telnet session Terminate a suspended telnet Resume connection and log out using the quit command Use the disconnect command on the router you Telnnetted from Cisco Discovery Protocol The Cisco Discovery
200. ozen years of history you get to today s networking environment where a computer vendor couldn t sell a computer without it also supporting TCP IP Problem solved Well before TCP IP became the networking protocol standard solving all these problems the International Organization for Standardization ISO worked hard on a set of protocols that together fit into an architecture called Open System Interconnection OSI As you recall from Chapter 2 The TCP IP and OSI Networking Models OSI defined its own protocols for Layers 3 through 7 relying on other standards for Layers 1 and 2 much like TCP IP does today OSI did not become commercially viable whereas TCP IP did the victory going to the nimbler more flexible TCP IP So why bother telling you all this now Well OSI defines a network layer protocol called the Connectionless Network Protocol CLNP It also defines a routing protocol a routing protocol used to advertise CLNP routes called Intermediate System to Intermediate System IS IS IS IS advertises CLNP routes between intermediate systems which is what OSI calls routers Routing Protocol Overview 419 Later in life IS IS was updated to include the capability to advertise IP routes as well as CLNP routes To distinguish it from the older IS IS this new updated IS IS is called Integrated IS IS The word integrated identifies the fact that the routing protocol can exchange routing information for multiple Laye
201. part identifies which group this address is a member of Answer Network number and node number are the two main parts of an IPX address Addresses with the same network number are in the same group On LAN interfaces the node number is made to have the same value as the LAN MAC address 8 Name the two main parts of an IP address Which part identifies which group this address is a member of Answer Network and host are the two main parts of an IP address As described in Chapter 5 technically there are three portions of the IP address network subnet and host However because most people think of the network and subnet portions as one portion another correct answer to this question using popular terminology would be subnet and host In short without subnetting the network part identifies the group with subnetting the network and subnet part together identifies the group 9 PC1 sends data to PC2 using TCP IP Three routers separate PC1 and PC2 Explain why the statement PC1 sends an Ethernet frame to PC2 is true or false Answer False Packets are delivered from end to end across a network whereas frames simply pass between devices on each common physical network The intervening routers discard the original Ethernet header replacing it with other data link headers as needed A truer statement would be PC1 sends an IP packet to PC2 10 In IP addressing how many octets are in 1 byte Answer One Octet is a gene
202. pe has been used in other Cisco courses so you also should know this term It refers to the type of routing protocol such as link state or distance vector Table 14 8 lists some of the major comparison points between interior routing protocols Foundation Summary 423 Table 14 8 Major Comparison Points Between Interior Routing Protocols Point of Comparison Description Type of routing Each interior routing protocol covered in this chapter can be protocol characterized based on the underlying logic used by the routing protocol This underlying logic often is referred to as the type of routing protocol The three types are distance vector link state and hybrid Full partial updates Some interior routing protocols send their entire routing tables regularly which is called full routing updates Other routing protocols send only a subset of the routing table in updates typically just the information about any changed routes This is called partial routing updates Partial updates require less overhead in the network Convergence Convergence refers to the time required for routers to react to changes for example link failures and router failures in the network removing bad routes and adding new better routes so that the current best routes are in all the routers routing tables Metric The numeric value that describes how good a particular route is The lower the value is the better the route is Some metrics provid
203. pe of routing protocol Each interior routing protocol covered in this chapter can be characterized based on the underlying logic used by the routing protocol This underlying logic often is referred to as the type of routing protocol The three types are distance vector link state and hybrid Full partial updates Some interior routing protocols send their entire routing tables regularly which are called full routing updates Other routing protocols send only a subset of the routing table in updates typically just the information about any changed routes This subset is referred to as partial routing updates Partial routing updates require less overhead in the network Convergence Convergence refers to the time required for routers to react to changes for example link failures and router failures in the network removing bad routes and adding new better routes so that the current best routes are in all the routers routing tables Metric The metric refers to the numeric value that describes how good a particular route is The lower the value is the better the route is Some metrics provide a more realistic perspective on which routes are truly the best routes Support for VLSM Variable length subnet masking VLSM means that in a single Class A B or C network multiple subnet masks can be used The advantage of VLSM is that it enables you to vary the size of each subnet based on the needs of that subnet F
204. plain the function of the loopback and collision detection features of an Ethernet NIC in relation to half duplex and full duplex operations Answer The loopback feature copies the transmitted frame back onto the receive pin on the NIC interface The collision detection logic compares the received frame to the transmitted frame during transmission if the signals do not match a collision is occurring With full duplex operation collisions cannot occur so the loopback and collision detection features are purposefully disabled and concurrent transmission and reception is allowed Describe the benefit of the Spanning Tree Protocol as used by transparent bridges and switches Answer Physically redundant paths in the network are allowed to exist and be used when other paths fail Also loops in the bridged network are avoided Loops are particularly bad because bridging uses LAN headers which do not provide a mechanism to mark a frame so that its lifetime can be limited in other words the frame can loop forever Name the three reasons why a port is placed in forwarding state as a result of spanning tree Answer First all ports on the root bridge are placed in forwarding state Second one port on each bridge is considered its root port which is placed in forwarding state Finally on each LAN segment one bridge is considered to be the designated bridge on that LAN that designated bridge s interface on the LAN is placed in a forwarding
205. protocols covered in this chapter support VLSM Answer RIP 2 EIGRP OSPF Integrated IS IS and BGP 2 Which IP routing protocols covered in this chapter use distance vector logic Answer RIP 1 RIP 2 and IGRP 3 Which interior IP routing protocols covered in this chapter are considered to converge quickly Answer EIGRP OSPF and Integrated IS IS 4 Compare distance vector and link state protocols in terms of what information is sent in routing updates Answer Distance vector protocols send sparse information typically describing a subnet and a metric for each route Link state protocols send much more detailed topology information describing each router and each link so that every router knows a full conceptual picture of the network 5 List three similarities between EIGRP s balanced hybrid logic and link state logic Answer Fast convergence neighbor discovery before sending routing information not sending of full updates on a regular period some topology tables built in addition to the IP routing table 10 11 Chapter 14 557 Explain the basic concept behind why some routing protocols support VLSM and some do not Answer VLSM implies that different subnet masks are used for different subnets of the same network To advertise subnets that have different sizes the routing protocol must include the subnet mask information for each subnet in the routing updates Routing protocols that do not support VLSM d
206. r If you do not know the answer to a question or are only partially sure of the answer you should mark this question wrong for purposes of the self assessment Giving yourself credit for an answer that you correctly guess skews your self assessment results and might provide you with a false sense of security 1 Which of the following routing protocols are considered to use distance vector logic a RIP b IGRP c EIGRP d OSPF e BGP 2 Which of the following routing protocols are considered to use link state logic a RIP V1 b RIP V2 c IGRP d EIGRP e OSPF f BGP g Integrated IS IS 3 Which of the following routing protocols use a metric that is by default at least partially affected by link bandwidth a RIP V1 b RIP V2 c IGRP Do I Know This Already Quiz 405 EIGRP OSPF BGP Integrated IS IS 4 Which of the following interior routing protocols support VLSM RIP V1 RIP V2 IGRP EIGRP OSPF Integrated IS IS 5 Which of the following situations would cause RIP to remove all the routes learned from a particular neighboring router a b c d Keepalive failure No longer receiving updates from that neighbor Updates received 5 or more seconds after the last update was sent to that neighbor Updates from that neighbor have the global route bad flag 6 Which of the following interior routing protocols are considered to be capable of converging quickly a b RIP V1 RIP
207. r 3 routed protocols Integrated IS IS has an advantage over OSPF because it supports both CLNP and IP route advertisement but most installations could not care less about CLNP Table 14 5 outlines the key comparison points with all Interior routing protocols for both Integrated IS IS and OSPF Table 14 5 IP Link State Protocols Compared Feature OSPF Integrated IS IS Period for individual reflooding of 30 minutes 15 minutes routing information Metric Cost Metric Supports VLSM Yes Yes Convergence Fast Fast Balanced Hybrid Protocols Enhanced IGRP EIGRP does not use distance vector or link state logic but instead it uses a whole new category of routing protocol This new category has some features similar to link state protocols others similar to distance vector protocols and yet others unlike either of the two Cisco sometimes categorizes EIGRP as a balanced hybrid protocol so you should remember the term The internal workings of EIGRP depend on an algorithm called the Diffusing Update Algorithm DUAL DUAL exchanges more topology information than a distance vector routing protocol but it does not transmit full topology information like a link state protocol Also the computations used by DUAL require far less processing than the computation intensive Dijkstra SPF algorithm DUAL defines a method for each router not only to calculate the best current route to each subnet but also to calculate alter
208. r data link layer functions Answer E Multimedia Cable Network Services MCNS defines a MAC layer that also uses IEEE 802 2 as part of the data link layer Which of the following protocols are used by a cable modem for the upstream data Answer B and E Which of the following remote access technologies uses ATM Ethernet and PPP as data link protocols Answer C Which of the following remote access technologies support specifications that allow both symmetric speeds and asymmetric speeds Answer A and C ISDN always uses symmetric speeds and cable modems always use asymmetric speeds Which of the following remote access technologies when used to connect to an ISP is considered to be an always on service Answer C and D Analog modems and ISDN lines must signal or dial to set up a circuit before any data can be passed whereas DSL and cable modems do not do this What do ISDN BRI and PRI stand for Answer ISDN stands for Integrated Services Digital Network BRI stands for Basic Rate Interface PRI stands for Primary Rate Interface 560 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 2 How many bearer channels are in a BRI What about a PRI in North America What about a PRI in Europe Answer BRI uses two bearer channels and one signaling channel 2B D PRI uses 23B D in North America and 30B D in Europe The signaling channel on BRI is a 16 kbps channel on PRI it is
209. r source traffic ISL Inter Switch Link The Cisco proprietary VLAN trunking protocol ISO International Organization for Standardization An international organization that is responsible for a wide range of standards including those relevant to networking The ISO developed the OSI reference model a popular networking reference model L4PDU The data compiled by a Layer 4 protocol including Layer 4 headers and encapsulated high layer data but not including lower layer headers and trailers Layer 3 protocol A protocol that it has characteristics like OSI Layer 3 which defines logical addressing and routing IP IPX and AppleTalk DDP are all Layer 3 protocols learn The process of discovering MAC addresses and their relative location by looking at the source MAC address of all frames received by a bridge or switch link state A type of routing protocol which sends full topology information about the network to all routers so they all have a consistent view of the network topology and status Link state algorithms create a consistent view of the network and therefore are not prone to routing loops however they achieve this at the cost of relatively greater computational difficulty and more widespread traffic LLC Logical Link Control The higher of the two data link layer sublayers defined by the IEEE Synonymous with IEEE 802 2 local loop A line from the premises of a telephone subscriber to the telephone company CO packet 58
210. re 14 4 RIP and IGRP Metrics Compared RIP Regardless of Bandwidth JE a eS en ER a S P r gt J Z Bandwidth 1544 So pa A 64 kbps B 1 Subnet 10 1 1 0 Routing Table Subnet Subnet Output Interface 10 1 1 0 So Bandwidth 1544 IGRP 7 FL Fe z Bandwidth 64 soj lt y A 64 kbps B j 2 Subnet 10 1 1 0 Routing Table Subnet Subnet Output Interface 10 1 1 0 S1 As shown in the figure Router B s route to 10 1 1 0 points through Router A because that route has a lower hop count 1 than the route through Router C 2 However Router B will 416 Chapter 14 Introduction to Dynamic Routing Protocols choose the two hop route through Router C when using IGRP because the bandwidths of the two links in the route are much higher than that of the single hop route In the top trio of routers the engineer let the bandwidth command default to 1544 on each link because RIP does not consider the bandwidth On the bottom trio the engineer correctly configured bandwidth to match the actual link speeds thereby allowing IGRP to choose the faster route The bandwidth interface subcommand does not change the actual physical speed of the interface it just tells the IOS what speed to assume the interface is using IGRP and RIP 1 were the main options for routing protocols back in the early 1990s RIP 2 came later but only after two better alternatives OSPF and EIGRP had become be
211. re 15 15 Cable TV Terminology Andy s PC Ethernet wef Cable Modem L L L i z F connectors L L A seme Head end a E 5 Andy s House AA E al P j 1 Distribution Cables Mayberry CATV i E Drop Cable Essentially the CATV signal is broadcast over the rest of the cable plant being amplified along the way A drop cable taps into the distibution cable that runs near your house and then enters your home and connects to the back of a wall plate near your TV You just need to run the short coax cable from the back of your TV to the wall plug and the cabling is complete Because most people will want to watch TV as well possibly multiple TVs the drop cable must be split Splitting does not mean literally taking the wire out of the cable and cutting it in half instead it means that you use a small device that passively lets the signal coming in from the street pass through to other cables in your house You can use the same kind of line splitter when using a cable modem that you use when you connect two TVs to the cable TV line at the same time In the figure the splitter connects to the drop cable as well as the two cables connecting to the cable modem and the TV The splitter just takes the incoming signal 462 Chapter 15 Remote Access Technologies Layer from the drop cable and passes it out both of the other lines Note that the connector the round connector common on most CATV cabling is c
212. ream 18 000 feet IDSL 2B1Q and downstream speed Symmetric DSL None 2B1Q 768 kbps for both upstream 22 000 feet SDSL and downstream speed High data rate ITU G 991 1 2B1Q 1 544 or 2 048 Mbps for 12 000 feet DSL HDSL ANSI TR 28 both upstream and downstream speed G SHDSL ITU G 991 2 Trellis coded pulse 192 kbps to 2 360 Mbps for 28 000 feet A wide variety of standards bodies and vendor consortiums helped develop these standards As you might imagine with so many standards many different organizations pushed for standards that best met their needs Over time the number of differing standards will stabilize The following organizations are among the key players in the development of DSL m American National Standards Institute ANSI m Institute of Electrical and Electronics Engineers IEEE m International Telecommunications Union ITU m European Telecommunications Standards Institute ETSI m DSL Forum 457 458 Chapter 15 Remote Access Technologies DSL Protocols DSL itself provides a Layer 1 transmission path between two endpoints in some ways like the Layer 1 service that analog modems and ISDN modems provide However DSL uses some additional protocols to support data transfer For instance DSL uses ATM as the Layer 2 protocol between the DSL router or DSL modem in the home and the ISP router Additionally DSL uses a protocol called PPP over ATM PPPoA PPP and ATM are both data link protocols but t
213. removing the need to be compatible with the entirety of the core of the PSTN DSL can be defined to provide some nice services and better transmission speeds DSUs basic services have some similarities as well as differences when compared to analog modems and ISDN lines Some of the key features are as follows m DSL allows analog voice signals and digital data signals to be sent over the same local loop wiring Digital Subscriber Line 455 m Similar to ISDN the local loop must be connected to something besides a traditional voice switch at the local CO a device called a DSL access multiplexer DSLAM m DSL allows for a concurrent voice call to be up at the same time as the data connection m Unlike modems and ISDN DSUs data component is always on in other words you don t have to signal to set up a data circuit DSL really does provide some great benefits you can use the same old phones that you already have you can keep the same phone number and you can just sit down at your PC at home and start using the Internet Figure 15 13 shows some of the details of a typical DSL connection Figure 15 13 DSL Connection from the Home IP Network Owned by ISP Andy s PC IP Traffic Split to ISP Ethernet Digital Router Signals gt 4000 Hz Local Loop DSL Router Modem Y Analog Voice Split to Voice Switch DTMF Tones Analog Voice Andy s 0 4000 Hz Analog phone Voic
214. rent No Yes Yes Yes voice and data Always on No No Yes Yes Local loop distance No No Yes distance No Foundation Summary 467 Foundation Summary The Foundation Summary section of each chapter lists the most important facts from the chapter Although this section does not list every fact from the chapter that will be on your CCNA exam a well prepared CCNA candidate should know at a minimum all the details in each Foundation Summary section before going to take the exam Figure 15 17 depicts the PSTN and how it supports analog voice through a digital T1 core Figure 15 17 Analog Voice Calls Through a Digital PSTN Andy s phone Local Loop Analog Table 15 9 lists some of the key modem standards PCM Codec Converts Analog lt gt Digital Telco Voice Switch Mayberry CO Table 15 9 Modem Standards Standard Speed PSTN PCM Codec Converts Analog lt gt Digital Digital T1 Line 24 separate 64Kbps DSO a Channels P gt Telco Voice Switch Raleigh CO Comments Barney s phone L Local Loop Analog V 22 1200 bps 600 baud Mainly used outside the United States V 22bis 2400 bps 600 baud First widely deployed worldwide standard V 32 4800 9600 2400 baud Adjusts speed based on line quality V 32bis 14 4kbps 2400 baud Backward compatible with V 32 continues
215. resses of the name servers are shown in the ip name server command Up to six DNSs can be listed they are searched for each request sequentially based on the order in the command Finally the ip domain lookup command enables IOS to ask a name server IP domain lookup is the default no ip domain lookup disables the DNS client function For names that do not include the full domain name the ip domain name command defines the domain name that should be assumed by the router The show ip host command lists the static entries in addition to any entries learned from a DNS request Only the three static entries were in the table in this case The term perm in the output implies that the entry is static Also note that when short names are used in other words the name does not include the DNS domain name the router adds the domain name of gileadfoundation org as configured in the ip domain name gileadfoundation org command Table 13 7 summarizes the key naming commands in IOS Table 13 7 IP Naming Commands Function Command Options Tell IOS to use a DNS __ Configure the ip domain lookup global configuration command Configure IP Configure the ip name server svr1 svr2 global configuration addresses of name command servers Configure static host Use the ip host name address command names List current hostname Use the show hosts exec command information IP Troubleshooting Features 389 Telnet and S
216. riali ip address 163 1 13 201 255 255 255 128 EthernetO ip address 163 1 1 201 255 255 255 128 l router rip network 163 1 0 0 Scenario Part A Planning 487 16 2 R2 Configuration hostname R2 interface Seriald ip address 163 1 12 202 255 255 255 128 l interface Seriali encapsulation ppp ip address 163 1 23 202 255 255 255 128 l EthernetO ip address 163 1 2 202 255 255 255 128 router rip network 163 1 0 0 the following 2 commands configure RIP 16 3 R3 Configuration hostname R3 l interface Seriald ip address 163 1 13 203 255 255 255 128 l interface Seriali encapsulation ppp ip address 163 1 23 203 255 255 255 128 l EthernetO ip address 163 1 3 203 255 255 255 128 router rip network 163 1 0 0 488 Chapter 16 Final Preparation Example 16 4 SW3 Configuration Switch gt enable Switch configure terminal Enter configuration commands one per line End with CNTL Z Switch config hostname SW3 SW3 config enable secret cisco SW3 config line vty 0 15 SW3 config line password cisco SW3 config line login SW3 config line line con 0 SW3 config line login Login disabled on line until password is set SW3 config line password cisco SW3 config line interface vlan 1 SW3 config if ip address 163 1 1 213 255 255 255 128 SW3 config if no shutdown SW3 config if exit SW3 config ip default gateway 163 1 1 201 SW3 config int
217. ric word to describe a single byte Each IP address is 4 bytes or four octets long 11 Describe the differences between a routed protocol and a routing protocol Answer The routed protocol defines the addressing and Layer 3 header in the packet that actually is forwarded by a router The routing protocol defines the process of routers exchanging topology data so that the routers know how to forward the data A router uses the routing table created by the routing protocol when choosing where to route a packet 12 Name at least three routed protocols Answer TCP IP IP Novell IPX OSI CLNP DECnet CLNP AppleTalk DDP and VINES are some examples of routed protocols 13 Name at least three IP routing protocols Answer IP RIP IP IGRP IP IPX AppleTalk EIGRP IP OSPF OSI NLSP and OSI IS IS are some examples of routing protocols 14 15 16 17 18 19 20 21 Chapter5 513 Imagine an IP host on an Ethernet with a single router attached to the same segment In which cases does an IP host choose to send a packet to this router instead of directly to the destination host and how does this IP host know about that single router Answer Typically an IP host knows to what router to send a packet based on its configured default router If the destination of the packet is in another subnet the host sends the packet to the default router Otherwise the host sends the packet directly to the destination hos
218. rlier in this chapter you read about how to configure IP addresses and how to perform some basic troubleshooting For troubleshooting you have seen how to look at the routing table with the show ip route command how to look at interface status with several options on the show interfaces command and how to use standard and extended ping commands for basic troubleshooting TCP IP includes a protocol specifically to help manage and control the operation of a TCP IP network called the Internet Control Message Protocol ICMP The ICMP protocol provides a wide variety of information about the health and operational status of a network Control Message is the most descriptive part of the name ICMP defines messages that helps control and manage the work of IP and therefore is considered to be part of TCP IP s network layer Because ICMP helps control IP it can provide useful troubleshooting information In fact the ICMP messages sit inside an IP packet with no transport layer header at all so it is truly just an extension of the TCP IP network layer RFC 792 defines ICMP and includes the following excerpt which describes the protocol well Occasionally a gateway router or destination host will communicate with a source host for example to report an error in datagram processing For such purposes this protocol the Internet Control Message Protocol ICMP is used ICMP uses the basic support of IP as if it were a higher level protocol howe
219. rough the labs and their solutions if your time is limited but you might want to at least try to write down the solution before looking at the answer Listing of the Hands on Exercises To best use NetSim you should first pick a particular lab or scenario You might even want to print a copy if the lab or scenario is in one of the CD only appendixes Then you can bring up NetSim and select the corresponding NetSim lab topology that matches the lab or scenario NetSim creates a simulated network that matches the lab or scenario so all you have to do is start entering commands just as if it were a real network with real gear The scenarios and labs are located in a couple different places First Chapter 18 Final Preparation includes one scenario It covers a lot of different topics from the book The CD contains a scenarios appendix CD only Appendix B Scenarios and a lab appendix CD only Appendix C Hands on Lab Exercises These scenarios and labs focus on a more specific set of topics If you plan to use NetSim frequently you should probably print the CD only Appendixes B and C In CD only Appendix B the scenarios are numbered in a way to help remind you of the corresponding chapter in the book For instance Scenario 1 reinforces topics covered in Chapter 7 Operating Cisco Routers and Scenario 3 covers the same commands covered in Chapter 8 Operating Cisco LAN Switches Table C 1 lists the different
220. routing protocols covered in this chapter use distance vector logic Which interior IP routing protocols covered in this chapter are considered to converge quickly Compare distance vector and link state protocols in terms of what information is sent in routing updates List three similarities between EIGRP s balanced hybrid logic and link state logic Explain the basic concept behind why some routing protocols support VLSM and some do not Explain the difference between interior and exterior routing protocols Explain the difference between full and partial routing updates Define the term balanced hybrid in relation to the terms distance vector and link state Compare and contrast the types of information sent in distance vector routing updates versus link state routing updates What term describes the underlying logic behind the OSPF routing protocol Cisco Published INTRO Exam Topics Covered in This Part 9 Describe and install the hardware and software required to be able to communicate via a network 13 Define and describe the structure and technologies of computer networks 14 Describe the hardware and software required to be able to communicate via a network 17 Identify the key characteristics of common wide area networking WAN configurations and technologies and differentiate between these and common LAN technologies 19 Describe the role of a router in a WAN Always re check www cisco com for the latest posted
221. rs Noticing that a collision has occurred in an upstream cable channel is much more difficult than with an Ethernet Cables inside the CATV cable plant might be miles long which means that a device would have to wait longer for the electrical signal from a collision to return So the CSMA CD algorithm used by Ethernet does not work well on the upstream channel Instead MCNS defines the use of a multiplexing method called time division multiple access TDMA in which each home user is granted regular time periods during which to send upstream data These time slots happen multiple times per second By using TDMA most collisions can be avoided 464 Chapter 15 Remote Access Technologies The upstream channel uses the same data link protocols as the downstream channel with MAC addressing but it uses different modulation schemes The upstream channel uses quaternary phase shift keying QPSK or QAM 16 QPSK modulates the signal using phase shifts while QAM uses amplitude modulation Both the downstream and upstream channels compete with other users for the use of the channel So as more subscribers are added the actual throughput of the connection actually can slow down Table 15 7 summarizes some of the key points about the upstream data channel Table 15 7 Upstream Data over Cable Interesting Facts Downstream Rate OSI Layer 1 QPSK and QAM 16 OSI Layer 2 MCNS MAC and IEEE 802 2 LLC Multiplexing used Time division m
222. rs and they both use cable modems Describe the type of traffic that they could generate that could cause collisions and tell what is done to help prevent those collisions Answer Downstream data never can cause a collision with upstream data because the two are sent in different frequency ranges Because only the head end sends downstream data no collisions can occur Upstream data from all subscribers uses the same frequency range so data sent to the head end by Andy and Barney could collide Cable standards use a feature called time division multiple access TDMA to assign time slots to each subscriber This prevents most collisions so no collisions should occur 16 Name the four different Layer 1 encoding methods defined for use by cable modems For each one list whether it is used for upstream data downstream data or both Answer QAM 64 and QAM 256 are both available for use as downstream encoding methods QAM 16 and QPSK are both available for upstream encoding 17 Which of the four different remote access technologies support IP TCP UDP and the rest of the higher layer TCP IP protocols Answer All of them 18 19 20 Chapter 15 563 Compare and contrast the cabling used by an analog modem and a DSL router modem when connecting to the local phone company line Identify the purpose of each pin on the connector Answer Both use a cable with two wires using an RJ 11 connector Pin 3 is used for transmit pin 4
223. ry for the purpose of NVRAM but Cisco would not ask such trivia on the test What is the intended purpose of RAM in a Cisco 2950 switch Answer RAM is used as IOS working memory storing such things as MAC address tables and frames and for IOS code storage What command sets the password that would be required after typing the enable command Is that password encrypted by default Answer enable password or enable secret The password in the enable command is not encrypted by default The enable secret password is encrypted using MDS 528 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 14 Is the password required at the console the same one that is required when Telnet is used to access a switch Answer No The Telnet virtual terminal password is not the same password although many installations use the same value 15 Name two commands used to view the configuration to be used at the next reload of a 2950 switch Which one is a more recent addition to IOS Answer show config and show startup config show startup config is the newer one and hopefully is easier to remember 16 Name two commands used to view the configuration that is currently used in a 2950 switch Which one is a more recent addition to IOS Answer write terminal and show running config show running config is the newer command and hopefully is easier to remember Chapter 9 Do Know This Already Quiz
224. s FDDI address and burned in address are all synonymous with MAC address All of these names are used casually and in formal documents and they refer to the same 6 byte MAC address concept as defined by IEEE 5 What portion of a MAC address encodes an identifier representing the manufacturer of the card Answer The first 3 bytes called the Organizationally Unique Identified OUI comprise the portion of a MAC address that encodes an identifier representing the manufacturer of the card 6 Are MAC addresses defined by a Layer 2 or Layer 3 protocol Answer MAC addresses are defined by a Layer 2 protocol Ethernet and Token Ring MAC addresses are defined in the 802 3 and 802 5 specifications 7 How many bits are present in a MAC address Answer MAC addresses have 48 bits The first 24 bits for burned in addresses represent a code that identifies the manufacturer 8 Name the two main parts of a MAC address Which part identifies which group this address is a member of Answer There are no parts and nothing defines a grouping concept in a MAC address This is a trick question Although you might have guessed that the MAC address has two parts the first part dictated to the manufacturer and the second part made up by the manufacturer there is no grouping concept 9 What OSI layer typically encapsulates using both a header and a trailer Answer The data link layer typically encapsulates using both a header and a trai
225. s You can improve your hands on skills whether you perform these exercises using real gear perform them using NetSim or just read through the exercises Scenarios In this Cisco Press Exam Certification Guide series scenarios include some form of a problem statement asking you to solve the problem Then a suggested solution is shown with an explanation of some of the pitfalls you might have encountered with your answer Many of these scenarios include configuration and EXEC commands but some do not These scenarios are designed so that if you don t have access to real hardware you can still learn more about the commands on routers and switches These same scenarios can also be performed using NetSim Labs Hands on Exercises Available with NetSim 573 This book also includes lab exercises which follow a format typical of labs used in networking courses These labs give you more guidance than do the scenarios For instance the scenarios simply state a goal such as Configure these three routers to support a full mesh of PVCs whereas a lab gives you instructions for each step you need to take to configure the network You simply read the lab instructions and the lab guides you through the steps required to configure a network based on a stated set of requirements As with the scenarios you can perform these labs on real gear or using the special NetSim build included with the CD that comes with this book You can also just read th
226. s Fred the ICMP Destination Unreachable message with the code protocol unreachable in response to Fred s packet destined for 10 1 2 14 IP Troubleshooting Features 387 m Port unreachable The final code field value is more likely today If the server is up but the web server software is not running the packet can get to the server but cannot be delivered to the web server software The web server host sends Fred the ICMP Destination Unreachable message with the code port unreachable in response to Fred s packet destined for 10 1 2 14 One key to troubleshooting with the ping command is understanding the various codes the command uses to signify the various responses it can receive Table 13 6 lists the various codes that the Cisco IOS software ping command can supply Table 13 6 Codes That the ping Command Receives in Response to Its ICMP Echo Request ping Command Code Description ICMP Echo Reply received Nothing was received before the ping command timed out ICMP unreachable destination received ICMP unreachable network received ICMP unreachable port received ICMP source quench received ZIO TV ZIS ICMP Can t Fragment message received u Unknown packet received IP Naming Commands When using the IOS CLI you will want to refer to names instead of IP addresses Particularly for the trace ping and telnet commands the IP address or host name must be s
227. s and switches existed all devices were cabled to the same shared Ethernet The CSMA CD algorithm was used to determine who got to send across the Ethernet As the amount of traffic increased collisions and waiting because of CSMA CD increased so frames took longer to send Switches separated the network into multiple collision domains typically one per port reducing collisions and allowing devices on opposite sides of the bridge to send concurrently What are two key differences between a 10 Mbps NIC and a 10 100 NIC Answer The obvious benefit is that the 10 100 NIC can run at 100 Mbps The other benefit is that 10 100 NICs can autonegotiate both speed and duplex between themselves and the device that they are cabled to typically a LAN switch Assume that a building has 100 devices attached to the same Ethernet These users then are migrated onto two separate shared Ethernet segments each with 50 devices with a transparent bridge between them List two benefits that would be derived for a typical user Answer Fewer collisions due to having two collision domains Also less waiting should occur because twice as much capacity exists Assume that a building has 100 devices attached to the same Ethernet These devices are migrated to two different shared Ethernet segments each with 50 devices The two segments are connected to a Cisco LAN switch to allow communication between the two sets of users List two benefits that would be deri
228. s the configuration in RAM for normal operations 4 What type of router memory is used to store the operating system used for low level debugging and not for normal operation Answer B The ROMMON operating system is stored in ROM 5 What command copies the configuration from RAM into NVRAM Answer F The first parameter identifies the source of the config and the last parameter identifies the destination Q amp A 10 Chapter7 519 What mode prompts the user for basic configuration information Answer D Which of the following could cause a router to change the IOS that is loaded when the router boots Answer D and F The boot command is a configuration command that identifies the source and possibly the name of the IOS to load The configuration register tells the router the source from which to find the file containing the IOS Which of the following hexadecimal values in the last nibble of the configuration register would cause a router to not look in Flash memory Answer A and B A 0 makes the router load ROMMON code a 1 makes the router load the RXBOOT IOS image Imagine that you have configured the enable secret command followed by the enable password command from the console You log out of the router and log back in at the console Which command defines the password that you had to type to access the router again from the console Answer C The password subcommand under the line console 0 command sets
229. se services are always on List some of the pros and cons regarding the use of analog modems for remote access Answer Modems have the great advantage of being the most pervasively available remote access technology The history of modems is long with modems growing to be a very reliable choice for remote access Speeds have improved over the years with compression technology increasing the effective throughput to beyond 100 kbps The biggest negatives about using modems include their relatively low speed and the fact that you cannot use the phone at the same time as you send data List some of the pros and cons regarding the use of ISDN for remote access Answer ISDN s advantages include the capability to support voice calls concurrently with a data call Also ISDN can be used over the local telco loop with no significant distance limitations And it provides more bandwidth than do modems particularly with both B channels dialed to the same remote site ISDN does have a few disadvantages with the biggest disadvantage being the lower speeds than DSL or cable List some of the pros and cons regarding the use of DSL for remote access Answer DSL provides high speed Internet access to the home exceeding downstream speeds of 1 Mbps It supports concurrent voice and data with the data service always being turned on no dialing is required And the service speed does not degrade when more users are added to the network However
230. sound waves using a speaker that is inside the part of the phone that you put next to your ear The analog electrical signals used to represent sound can be shown on a graph as in Figure 15 1 436 Chapter 15 Remote Access Technologies Figure 15 1 Analog Electrical Signal Frequency Amplitude and Phase Voltage Amplitude Wavelength 3 Wavelengths in Second 3 Hz Frequency The graph represents the three main components of the signal m Frequency Frequency is defined as how many times the signal would repeat itself from peak to peak in 1 second assuming that the sound didn t change for a whole second The figure shows a frequency of 3 Hertz Hz The greater the frequency of the electrical signal is the higher the pitch is of the sound being represented m Amplitude The amplitude represents how strong the signal is a higher amplitude peak represents a louder sound m Phase Phase refers to where the signal is at a point in time at the top going down at the bottom going up and so on The goal of the original PSTN was to create a circuit between any two phones Each circuit consisted of an electrical path between two phones which in turn supported the sending of an analog electrical signal in each direction allowing the people on the circuit to have a conversation Remember the original PSTN built by Alexander Graham Bell s new company predated the first vacuum tube computers so the concept of support d
231. st addresses namely 200 1 1 129 to 200 1 1 158 14 Given the IP address 220 8 7 100 and the mask 255 255 255 240 what are the assignable IP addresses in this subnet Answer The subnet number is 220 8 7 96 and the subnet broadcast address is 220 8 7 111 The assignable addresses are all the addresses between the subnet and broadcast addresses namely 220 8 7 97 to 220 8 7 110 15 Given the IP address 134 141 7 7 and the mask 255 255 255 0 what are all the subnet numbers if the same static mask is used for all subnets in this network Answer The answer is 134 141 1 0 134 141 2 0 134 141 3 0 and so on up to 134 141 254 0 134 141 0 0 is the zero subnet and 134 141 255 0 is the broadcast subnet 16 17 Chapter 12 547 Given the IP address 220 8 7 100 and the mask 255 255 255 240 what are all the subnet numbers if the same static mask is used for all subnets in this network Answer The answer is not as obvious in this question The Class C network number is 220 8 7 0 The mask implies that bits 25 through 28 which are the first 4 bits in the fourth octet comprise the subnet field The answer is 220 8 7 16 220 8 7 32 220 8 7 48 and so on through 220 8 7 224 220 8 7 0 is the zero subnet and 220 8 7 240 is the broadcast subnet The following table outlines the easy decimal algorithm to figure out the subnet numbers Octet 1 2 3 Comments Network number 220 8 7 Mask
232. state 534 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 21 Name the three interface states that the Spanning Tree Protocol uses other than forwarding Which of these states is transitory Answer Blocking Layer 2 listening and learning Blocking is the only stable state the other two are transitory between blocking and forwarding Chapter 10 Do Know This Already Quiz 1 1 In a LAN which of the following terms best equates to the term VLAN Answer B By definition a VLAN includes all devices in the same LAN broadcast domain Imagine a switch with three configured VLANs How many IP subnets would be required assuming that all hosts in all VLANs want to use TCP IP Answer D The hosts in each VLAN must be in different subnets Which of the following fully encapsulates the original Ethernet frame in a trunking header Answer B ISL fully encapsulates the original frame whereas 802 1q simply adds an additional header inside the original Ethernet frame Which of the following allows a spanning tree instance per VLAN Answer D Imagine a Layer 2 switch with three configured VLANs using an external router for inter VLAN traffic What is the least number of router Fast Ethernet interfaces required to forward traffic between VLANs Answer B You can use one Fast Ethernet interface and use trunking between the router and the switch A router is required to forward traf
233. subcommand logging synchronous Line subcommand Configuring IP Addresses 369 Table 13 3 IP EXEC Commands Command Function show hosts Lists all host names and corresponding IP addresses show interfaces type number Lists interface statistics including IP address show ip interface type number Provides a detailed view of IP parameter settings per interface show ip interface brief Provides a summary of all interfaces and their IP addresses show ip route ip address mask longer prefixes protocol Shows entire routing process id table or a subset if other parameters are entered show ip arp ip address host name mac address type number Displays IP ARP cache debug ip packet Issues log messages for each IP packet terminal ip netmask format bitcount decimal hexadecimal Sets type of display for subnet masks in show commands ping protocol tag host name system address Sends and receives ICMP echo messages to verify connectivity trace protocol destination Sends a series of UDP packets with increasing TTL values to verify the current route to a host Most of the examples in this chapter refer to the routers in Figure 13 1 The figure shows a simple network with three routers with each pair of routers having a serial link to the other two routers and a local Ethernet 370 Chapter 13 Basic Router Configuration and Operation
234. t because it is in the same subnet and by definition must be on the same data link Name three items in an entry in any routing table Answer A number that identifies a group of addresses the interface out which to forward the packet and the Layer 3 address of the next router to send this packet to are three items that you will always find in a routing table entry For instance IP routes contain subnet numbers the outgoing interface and the IP address of the next hop router Name the parts of an IP address when subnetting is used Answer Network subnet and host are the three parts of an IP address However many people commonly treat the network and subnet parts of an address as a single part leaving only two parts the subnet and host parts On the exam the multiple choice format should provide extra clues as to which terminology is used How many valid IP addresses exist in a Class A network You may refer to the formula if you do not know the exact number Answer 16 777 214 derived by the formula O78 2D How many valid IP addresses exist in a Class B network You may refer to the formula if you do not know the exact number Answer 65 534 derived by the formula G9 How many valid IP addresses exist in a Class C network You may refer to the formula if you do not know the exact number Answer 254 derived by the formula 28 2 What values can a Class A network have in the first octet Answer 1 through 1
235. t bits to use to represent that single sample So PCM sampling at 8000 times per second finds the best match of frequency amplitude phase in the table finds the matching 8 bit code and sends those 8 bits as a digital signal The PCM codec converts from digital to analog by reversing the process The decoding process re creates the analog signal but not quite exactly For instance if the original 440 Chapter 15 Remote Access Technologies frequency was 2139 3 the decoded frequency might be 2140 For normal speech the quality is great If you were trying to listen to DVD quality sounds over the telephone it probably wouldn t sound as good as it would if you were actually there but it s pretty close If you do the math you will notice that a single voice call requires 64 kbps of bandwidth in the digital part of the PSTN PCM says that you need to sample the analog signal 8000 times per second and each sample needs 8 bits to represent it A bright fellow at Bell Labs Nyquist did some research that showed this sampling rate was needed for digitized voice He noticed that the human voice could create sounds between 300 Hz and 3300 Hz and that the sampling rate needed to be twice that of the highest frequency So to overcome some other physics problems Nyquist and the team at Bell Labs decided to round that range of frequencies for the human voice to 0 Hz to 4000 Hz So because Nyquist s theorem states that you need twice the number of s
236. t has the DCE cable plugged into it In this case Seville was supplying clocking on both serial interfaces If no cable has been plugged in the IOS accepts the command If a DTE cable has been plugged in IOS rejects the command If you do not know which router has the DCE cable in it you can find out by using the show controllers command as shown at the end of the example In the example you can see that the output identifies the type of serial cable Also notice the bandwidth 128 command on serial 1 The bandwidth command tells IOS the speed of the link in kilobits per second regardless of whether the router is supplying IP Troubleshooting Features 381 clocking The bandwidth setting does not change anything that the router does at Layer 1 instead this setting is used by IOS software for other purposes For instance IGRP and EIGRP both use bandwidth to calculate a metric for routing protocols they use the bandwidth setting on the interfaces bandwidth defaults to T1 speed on serial interfaces There is no default for clock rate even with a DCE cable plugged in it must be configured IP Troubleshooting Features Cisco includes coverage of basic troubleshooting commands and concepts on the CCNA exams These commands are contained in several places in this book as well as in the CCNA ICND Exam Certification Guide This section covers some of the tools and commands specific to troubleshooting IP Internet Control Message Protocol Ea
237. t uses 10 1 1 200 and the web server uses 10 1 1 201 Mask 255 255 255 192 is used in all cases Is anything wrong with this network What is the easiest thing that could be done to fix it You can assume any working interior routing protocol Figure A 1 Example Network for Subnetting Questions 21 22 Chapter12 549 Answer Router A s Ethernet interface and Fred s Ethernet should be in the same subnet but they are not Fred s configuration implies a subnet with IP addresses ranging from 10 1 1 1 through 10 1 1 62 Router A s Ethernet configuration implies a subnet with addresses between 10 1 1 65 and 10 1 1 126 Also Router A s two interfaces must be in different subnets as configured they would be in the same subnet So the solution is to change Router A s Ethernet IP address to something between 10 1 1 1 and 10 1 1 62 making it be in the same subnet as Fred Referring to Figure A 1 Fred has been configured with IP address 10 1 1 1 mask 255 255 255 0 Router A s Ethernet has been configured with 10 1 1 100 mask 255 255 255 224 Router A s serial interface uses 10 1 1 129 mask 255 255 255 252 Router B s serial uses 10 1 1 130 mask 255 255 255 252 Router B s Ethernet uses 10 1 1 200 mask 255 255 255 224 and the web server uses 10 1 1 201 mask 255 255 255 224 Is anything wrong with this network What is the easiest thing that could be done to fix it You can assume any working interior routing protocol
238. t were created about 20 years ago when the processor in a routing device was probably less powerful than the processor in your cell phone today It had to be simple so as not to overburden the router s processor and also not to overload the network with overhead traffic The following list formalizes the basic distance vector logic and introduces a few important concepts that are explained over the next several pages Routers add directly connected subnets to their routing tables even without a routing protocol Routers send routing updates out their interfaces to advertise the routes that this router already knows These routes include directly connected routes as well as routes learned from other routers Routers listen for routing updates from their neighbors so that they can learn new routes The routing information includes the subnet number and a metric The metric defines how good the route is lower metric routes are considered better routes m When possible routers use broadcasts or multicasts to send routing updates By using a broadcast or multicast packet all neighbors on a LAN can receive the same routing information in a single update m fa router learns multiple routes to the same subnet the router chooses the best route based on the metric If the metrics tie there are a variety of options which are described in Chapter 6 OSPF and EIGRP Concepts and Configuration of the CCNA ICND Exam Certification Guide
239. tatus up and down is when the router does not receive keepalive messages on a regular basis Cisco routers send and expect to receive proprietary keepalive messages on each interface The purpose of the keepalives is to know whether the interface is usable For instance on a point to point link between Albuquerque and Yosemite each router sends a keepalive every 10 seconds As long as they each receive a keepalive every 10 seconds they think the link is up and up If Yosemite did not hear a keepalive for three times the keepalive interval default 10 second interval for a total of 30 seconds Yosemite would put the interface into an up and down status You can disable keepalives with the no keepalive interface subcommand or you can change the timer with the keepalive interval interface subcommand Those comments aside as long as an interface status is up and up the router believes that the interface is usable so the router can add the associated connected IP route to the routing table Configuring IP Addresses 379 In some cases you want an interface to be down for administrative reasons but you do not want to have to unconfigure it or pull out the cable to keep the interface from being up and up To bring down an interface for administrative reasons and as a side effect remove the connected route from the routing table you can use the shutdown interface subcommand as shown in Example 13 6 Example 13 6 Using the shutdown Command
240. ted by the data link network and transport layers respectively Answer Frame packet and segment respectively Explain the meaning of the term LSPDU Answer PDU stands for protocol data unit A PDU is the entity that includes the headers and trailers created by a particular networking layer plus any encapsulated data For instance an LSPDU includes Layer 5 headers and the encapsulated data Explain how Layer x on one computer communicates with Layer x on another computer Answer Each layer of a networking model works with the same layer on another computer with which it wants to communicate The protocol defined by each layer uses a header that is transmitted between the computers to communicate what each computer wants to do List the terms behind the acronym TCP IP Answer Transmission Control Protocol and Internet Protocol List the terms behind the acronym OSI Answer Open Systems Interconnection Chapter 3 Do Know This Already Quiz 1 Which of the following best describes the main function of OSI Layer 1 protocols Answer B 10 Q amp A Chapter3 503 Which of the following are part of the functions of OSI Layer 2 protocols Answer A Which of the following is true about Ethernet crossover cables Answer B Which of the following are true about the format of Ethernet addresses Answer B C and E Which of the following is true about the Ethernet FCS field Answer C Which
241. ted to hubs 6 What is the acronym and complete name of Cisco s proprietary trunking protocol over Ethernet Answer Inter Switch Link ISL 7 Consider the phrase A VLAN is a broadcast domain is an IP subnet Do you agree or disagree State your reasons Answer From one perspective the statement is false because an IP subnet is a Layer 3 protocol concept and a broadcast domain and VLAN are Layer 2 concepts However the devices in one broadcast domain comprise the exact same set of devices that would be in the same VLAN and in the same IP subnet 8 What fields are added or changed in an Ethernet header when using 802 1q Where is the VLAN ID in those fields Answer A new 4 byte 802 1q header which includes the VLAN ID is added after the source MAC address field The original FCS field in the Ethernet trailer is modified because the value must be recalculated as a result of changing the header 9 Compare and contrast the use of a Layer 3 switch versus an external router connected to a Layer 2 switch using a trunk for forwarding between VLANs Answer Functionally the end result of each process is identical However L3 switches optimize the internal processing of the switch using a very fast forwarding path typically using ASICs The end result is that L3 switches forward traffic between VLANs at much higher speeds than do externally attached routers 10 Chapter 11 537 Compare and contrast a Layer 3 switch wit
242. ter you now want to issue the show ip arp command What steps would you take to execute this command by using command recall keystrokes Answer Press the up arrow press Backspace five times and type arp The up arrow key retrieves the show ip route command Backspace moves the cursor backward and erases the character Typing inserts the characters into the line 10 11 12 13 14 Chapter 7 521 After typing show ip route 128 1 1 0 you now want to issue the command show ip route 128 1 4 0 What steps would you take to do so using command recall and command editing keystrokes Answer Press the up arrow or Ctrl p then press Ctrl b or the left arrow twice and press Backspace once and type 4 The Ctrl b and left arrow keys back up one character in the line without deleting the character The Backspace key deletes the 1 in this case And newly typed characters appear where the cursor sits in the command line What configuration command causes the router to require a password from a user at the console What configuration mode context must you be in That is what command s must be typed before this command after entering configuration mode List the commands in the order in which they must be typed while in config mode line console login Answer The line console 0 command is a context setting command it adds no information to the configuration The command can be typed from any part of configuration mode The l
243. testing IP connectivity from Albuquerque to Yosemite Figure 13 2 precedes the example as a reminder of the topology and IP addresses in the network IP Troubleshooting Features Figure 13 2 Sample Network Used for ping Example Bugs Daffy g g 10 1 1 0 ho 1 251 5 y on Albuquerque s1 10 1 130 251 10 1 128 251 i sO 10 1 128 252 sO 10 1 130 253 s0 ae 10 1 129 0 7 rel s J Sevill osemite 10 1 129 252 si ON ET 10 1 129 253 10 1 3 253 10 1 2 0 10 1 3 0 Sam Emma Elmer Red Example 13 8 Example with One Working ping and One Failing ping 383 Albuquerque show ip route Codes C connected S static I IGRP R RIP M mobile B BGP D EIGRP EX EIGRP external O OSPF IA OSPF inter area N1 OSPF NSSA external type 1 N2 OSPF NSSA external type 2 E1 OSPF external type 1 E2 OSPF external type 2 E EGP candidate default U per user static route o ODR P periodic downloaded static route Gateway of last resort is not set 10 0 0 0 24 is subnetted 3 subnets Cc 10 1 1 0 is directly connected EthernetO 0 10 1 130 0 is directly connected Seriali Cc 10 1 128 0 is directly connected SerialO Albuquerque ping 10 1 128 252 Type escape sequence to abort i IS IS L1 IS IS level 1 L2 IS IS level 2 ia IS IS inter area continues 384 Chapter 13 Basic Router Configuration and Operation Example 13 8 Example with One
244. the console password Imagine that you have configured the enable secret command followed by the enable password command from the console You log out of the router and log back in at the console Which command defines the password that you had to type to access privileged mode Answer B If both are configured the enable secret password is required to gain access to privileged mode What are the two names for the same CLI mode in a router that when accessed enables you to issue exec commands that could be disruptive to router operations Answer Enable mode and privileged mode Both names are commonly used and are found in Cisco documentation What are three methods of logging on to a router Answer Console auxiliary port and Telnet All three cause the user to enter user exec mode 520 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 3 What is the name of the user interface mode of operation used in which you cannot issue disruptive commands Answer User exec mode 4 Can the auxiliary port be used for anything besides remote modem user access to a router If so what other purpose can it serve Answer Yes For direct attachment of a terminal and dial for the purpose of routing packets Although it originally was created to support remote administration access many customers use an auxiliary port for dial backup particularly when analog lines are desired or when that is all that
245. the hop count Router B s metrics for its locally attached subnets are both 0 because there are no routers between B and those subnets Similarly Router A s metric for 162 11 8 0 is 0 Because Router B separates Router A from subnet 162 11 7 0 Router A s metric for subnet 162 11 7 0 is 1 Finally Router C s metric for subnet 162 11 7 0 is 2 because two routers separate it from that subnet You will learn much more about RIP and the underlying distance vector logic used by RIP as you prepare for the ICND exam For now this short list of RIP 1 features can help you compare RIP 1 to some of the other IP routing protocols covered in this overview m Based on distance vector Logic m Uses hop count for the metric m Sends periodic full routing updates every 30 seconds m Converges slowly often taking 3 to 5 minutes Does not support VLSM also making it a classful routing protocol 414 Chapter 14 Introduction to Dynamic Routing Protocols RIP Version 2 RIP Version 2 RIP 2 as currently defined in RFC 2453 defines several enhancements to the original RIP protocol RIP 2 uses distance vector logic uses hop count for the metric sends full periodic updates and still converges relatively slowly RIP 2 does add support for VLSM as compared with RIP 1 making it a classless routing protocol with RIP 2 including the subnet mask for each subnet in the routing updates Table 14 3 outlines the improvements made to RIP with the creation of
246. the source of the config and the last parameter identifies the destination What mode prompts the user for basic configuration information Answer D Imagine that you had configured the enable secret command followed by the enable password command from the console You log out of the switch and log back in at the console Which command defined the password that you had to type to access privileged mode again from the console Answer B When both are configured the enable secret password takes precedence over the enable password In what LED mode does the switch use the per port LEDs to show information about the current load on the switch Answer B Which of the following is not true of both a 2950 switch and Cisco routers Answer A 2950 switches do not have auxiliary ports What are the two names for the switch s mode of operation that when accessed enables you to issue commands that could be disruptive to switch operations Answer Enable mode and privileged mode Both names are commonly used and found in Cisco documentation 526 Appendix A Answers to the Do I Know This Already Quizzes and O amp A Sections 2 What are two methods of logging on to a switch Answer Console and Telnet Both cause the user to enter user exec mode 3 What is the name of the user interface mode of operation used when you cannot issue disruptive commands Answer User exec mode 4 What command would you use to receive
247. these subnets Following the show ip route command the example contains three commands that list information about the interfaces in the router The show ip interfaces brief command lists one line per interface with IP address information and interface status Next the show interfaces serial 0 command lists more details about a single interface with most of those details about the interface itself Finally the show ip interfaces serial 1 command shows detailed information about the IP protocol running over interface serial 1 IOS adds connected routes to the routing table that meet the following requirements m The interface has been configured with a valid IP address m The interface is in an up and up status according to the various interface oriented show commands All three of the show commands in Example 13 5 that list interface status information use two designations of up and up The first status keyword the first of the two ups in this case generally refers to OSI Layer 1 status For instance if there is no cable plugged in the first status word would be down instead of up The second status word generally refers to the status of OSI Layer 2 For instance if Seville defaulted to use HDLC on serial 0 but Albuquerque configured PPP as the data link protocol on its serial 1 interface on the other end of the link the interface status on each end would show up and down Another instance in which a router might put an interface in s
248. thoroughly When you move on to the next question you can t go back Some questions require that you drag and drop the answers into the correct slots in an answer area Exam question writers like to use this type of question for lists or sequences in particular Like all questions you can answer and then change the answer as long as you have not moved on to the next question yet For drag and drop questions many people benefit from moving the answers they are confident about into the presumably correct place and then they fit in the others in a lot of times that helps complete the answers correctly Just don t forget when you move on to the next question you can t go back m For simulated lab questions you should go back and confirm that any new configurations are working For instance if the question asks that you configure RIP but you do not see any routes when you use a show ip route command then you have not finished the question correctly The simulator used on the exam does work so that the show commands reflect what should actually be happening Many of the simulated lab questions require that you configure something but it will also be helpful if you know the pertinent show commands to verify the correct operation Also just for good measure save your configuration unless the question tells you not to That s a long list but hopefully it will help you prepare for taking the exam The most important tip is to simply relax
249. ting of IP packets in a Cisco router Tables 13 2 and 13 3 summarize many of the most common commands used for IP configuration and verification You can refer to other sources for more information about basic IP configuration on Cisco routers The Cisco IOS documentation is an excellent reference for additional IP commands see www cisco com univercd home home htm Also the Cisco Press book Interconnecting Cisco Network Devices is an excellent reference particularly if you are not able to attend the instructor led version of the class This chapter focuses on the most common commands the ones most likely to be on the CCNA exams Table 13 2 IP Configuration Commands Command Configuration Mode ip address ip address mask secondary Interface mode ip host name tcp port number address1 Global address2 address8 ip route network number network mask ip address Global interface distance name name ip name server server address1 server address2 server Global address6 ip domain lookup Global ip routing Global hostname name Global login Line configuration mode password value Line configuration mode enable password level level password encryption type encrypted password Global enable secret level level password encryption type encrypted password Global keepalive seconds Interface subcommand exec timeout minutes seconds Line
250. tion 2 Inthe previous question what would be the IP subnet of the link attached to serial 0 If another user wanted to answer the same question but did not have the enable password what command s might provide this router s addresses and subnets Answer The attached subnet is 8 0 2 0 255 255 255 0 The show interface show ip interface and show ip interface brief commands would supply this information as would show ip route The show ip route command would show the actual subnet number instead of the address of the interface 3 What must be done to make the output of the show ip route command list subnet masks in decimal format instead of prefixes In what mode would you use the command Answer You must use the terminal ip netmask format decimal command in enable mode 4 What are the differences between the clock rate and bandwidth commands Answer clock rate sets the physical Layer 1 actual transmission rate in bits per second and only when a DCE cable has been plugged into that interface The bandwidth command with units of kbps does not affect Layer 1 transmission rates Instead it is used by Cisco IOS Software as its understanding of the Layer 1 rate for purposes such as calculation of routing protocol metrics 5 Compare and contrast the commands used to set the enable console and telnet passwords on a router Answer The password command sets the console and telnet password When used as a line console 0 subc
251. to their hubs but put a bridge between the two hubs Barney wants to remove the hubs and connect all ten PCs to the same switch Comparing Fred and Barney s solutions which of the following is true Answer A B and D Imagine a network with three switches each with an Ethernet segment connecting it to the other two switches Each switch has some PCs attached to it as well Which of the following frames would cause loops if the Spanning Tree Protocol were not running Answer A and C Without STP any frame that a switch would forward out all ports would loop for an indefinitely long period of time Switches always forward broadcasts out all ports Likewise unicast frames to MAC addresses that are not in the MAC address table are flooded out all ports Which of the following interface states could a switch interface settle into after STP has completed building a spanning tree Answer B and C 530 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections Q amp A Name two of the methods of internal switching on typical switches today Which provides less latency for an individual frame Answer Store and forward cut through and Fragment Free switching Cut through switching has less latency per frame but does not check for bit errors in the frame including errors caused by collisions Store and forward switching stores the entire received frame verifies that the FCS is correct and then sends the frame
252. topology database using an algorithm called the Dijkstra Shortest Path First SPF algorithm This detailed topology information along with the Dijkstra algorithm helps link state protocols avoid loops and converge quickly Routing Protocol Overview 417 Link state protocols prevent loops from occurring easily because each router essentially has a complete map of the network If you take a trip in your car and you have a map you are a lot less likely to get lost than someone else who is just reading the signs by the side of the road Likewise the detailed topological information helps link state protocols easily avoid loops As you will read later the main reasons that distance vector protocols converge slowly are related to the loop avoidance features With link state protocols those same loop avoidance features are not needed allowing for fast convergence often in less than 10 seconds Open Shortest Path First OSPF is the most popular link state IP routing protocol today and is likely to be the most popular one for some time It works well is widely deployed and includes a wide variety of features that have been added over the years to accommodate new requirements The basic operation of OSPF differs from that of the distance vector protocols For the ICND exam you will need to know a few more details of course but for now a brief look at how OSPF works will help you compare it with distance vector protocols One difference relates
253. ts of the world Figure 15 8 shows the required ISDN hardware for a typical connection Figure 15 8 ISDN Local Loops and Equipment Andy s a PSTN _ No PCM Needed on Andy s Digital Local Loop RS 232 Cable Local Loop M Ta 09a BRD No PCM Needed No Analog Signal Telco ISDN a 5 a Switch Digital T1 Line 1 DSO Channel Local Loop Used Digital PRI Er Mayberry CO A R3 Telco ISDN Internal Switch ISDN Card Raleigh CO Notice that both the home PCs and the router at the ISP use ISDN gear Routers often use ISDN cards that can be connected directly to the ISDN circuit supplied by the telco PCs typically use an ISDN device called an ISDN terminal adapter TA which often is called an ISDN modem Because ISDN uses digital signals across the local loop it does not actually do any modulation or demodulation However the term ISDN modem emerged because it was cabled and installed similarly to an external analog modem So for the consumer marketplace the marketing people started calling TAs by the technically wrong but easy to understand term ISDN modem Note that the local loop from the home and the CO now connects to a device called an ISDN switch Local phone lines typically connect to a voice switch in the CO ISDN uses digitial signals so the telco actually must terminate the line from your house in a telco switch that expects digitial signals that conform to ISDN specifications Integrated Services D
254. tter options for most networks Table 14 4 summarizes some of the key comparison points between these three protocols Table 14 4 Distance Vector Protocols Compared Feature RIP 1 RIP 2 IGRP Update timer for full 30 seconds 30 seconds 90 seconds routing updates Metric Hop count Hop count Function of bandwidth and delay the default Can include reliability load and MTU Supports VLSM No Yes No Infinite metric value 16 16 4 294 967 295 Convergence Slow Slow Slow Link State Protocols OSPF and Integrated IS IS Link state and distance vectors share a common goal to fill the routing tables with the current best routes They differ significantly in how they each accomplish the task The largest difference between the two is that distance vector protocols advertise sparse information in fact distance vector protocols know only that other routers exist if the other router broadcasts a routing update to them When a distance vector protocol in a router hears a routing update the update says nothing about the routers beyond that neighboring router that sent the update Conversely link state protocols advertise a large amount of topological information about the network and the routers perform some CPU intensive computation on the topological data They even discover their neighbors before bothering to exchange routing information To figure out the current best routes a router processes the link state
255. two modems creates a physical network that has a lot of similarities with a leased point to point circuit Also analog modems typically transmit traffic asynchronously PPP supports both synchronous communication as typically is done over leased point to point lines as well as asynchronous communication which typically is done over dialed circuits using modems So PPP is the logical choice for a data link protocol when using modems today PPP includes some features that are important when using modems to dial into an ISP PPP includes the capability of dynamically assigning an IP address to a device on the other end of the PPP link So when you dial into an ISP the ISP dynamically assigns an IP address to your computer Also PPP supports that Challenge Handshake Authentication Protocol CHAP which popularly is used to allow the dial in user to supply a username and password to gain access to the ISP network CHAP is covered in the CCNA ICND Exam Certification Guide Analog Modems 445 Modem Installation and Cabling PC modems can be located internally or externally Internal modems are placed inside the PC itself whereas external modems are external to the PC Laptops might come with a modem built in or simply might use a convenient type of internal modem called a PCMCIA card or simply PC card PC cards are roughly the size of a credit card and easily can be inserted and removed from a PC Most PC hardware comes with either a serial comm
256. u should cover up portions of summary tables with a piece of paper forcing yourself to try to remember the details instead of just glancing at them Answer all the questions from inside the book again You should strive to master these questions so that you can answer the questions quickly If you are still slow in answering subnetting questions practice until you can find the subnet number and broadcast address when the mask is difficult within 1 minute You can use the CD based chapter with 25 subnetting practice questions for this exercise Before using the CD for general questions use the mode that lets you perform a simulated exam This will help you prepare for the exam experience Repeat answering all the questions on the CD until you can answer most of them almost automatically 480 Chapter 16 Final Preparation m Using a real set of routers and switches or using a simulation product such as Netsim which is included on the accompanying CD practice these basic skills Accessing a switch and a router Configuring basic administrative settings passwords host name IP addresses Practice configuring IP static routes and RIP Refer to Appendix C for a list of labs from this book that can be performed using the NetSim simulator that is included on the accompanying CD Preparing for the Actual Exam Experience For some of you either the INTRO exam or the CCNA exam will be your first experience
257. ultiple access TDMA Speed 320 kbps to 10 Mbps Cable Modem Summary Like DSL cable modems bring high speed remote access capabilities to the home The speeds might seem astounding 30 to 40 Mbps downstream is indeed impressive In fact I had a cable modem a few years ago and was one of the first people in my neighborhood to get it I surfed the web much faster from home than I did from the local Cisco Systems office The data service is always on even when someone is watching TV Because it doesn t use the telephone line at all you also can use the phone at the same time Cable modems do have a few drawbacks The per user data rates degrade as more users are added to the network Also because the network broadcasts all downstream traffic anyone can put a network analysis tool in their home and get a copy of what their neighbor is receiving Comparison of Remote Access Technologies This chapter scratches the surface of how modems ISDN cable and DSL work Consumers choose between these options for Internet access all the time and network engineers choose between these options for supporting their work at home users as well So it seems appropriate to close the chapter by listing some of the key comparison points for these options Comparison of Remote Access Technologies 465 The remote access technologies in this chapter provide services at Layer 1 and possibly Layer 2 of the OSI reference model TCP IP and all the assoc
258. unications port called a COM port or a Universal Serial Bus USB port Both USB and COM ports are intended to support external devices that communicate using a serial bit stream So External modems can be connected to a PC using either a COM port or a USB port Figure 15 7 depicts the typical topology Figure 15 7 Modem Installation Options and Concepts Phone Line Phone Line Phone Line Phone Line COMX gt E H Modem PC Card COM ports usually consist of either a female RS 232 connector which is a D shell connector with 25 pins or a DB 9 connector which uses 9 pins USB ports are rectangular female 446 Chapter 15 Remote Access Technologies connectors about one quarter inch by 1 inch long In either case the computer sends a serial bit stream to the external modem over the cable expecting the modem to send the data At the same time the modem forwards bits received from the phone line back to the PC Internal modems do not require the use of an RS 232 DB 9 or USB cable they simply connect directly to the phone line In the United States that means using the same type of cable that is used to connect to an analog phone with an RJ 11 connector However the installation of an internal modem still uses the logical concept of a COM port That is true of internal modems that are installed in an expansion card slot and of PCMCIA modems that simply can be inserted into the convenient PC card slot
259. upplied This section describes the use of host names on an IOS based device Along the way some nuances of the use of Telnet are covered IOS can use statically configured names as well as refer to one or more DNSs Example 13 9 shows some names statically configured with configuration pointing to two different DNSs Example 13 9 IP Naming Configuration and show host Command hostname Cooperstown l ip host Mays 10 1 1 1 ip host Aaron 10 2 2 2 ip host Mantle 10 3 3 3 l ip domain name gileadfoundation org ip name server 10 1 1 200 10 2 2 200 ip domain lookup continues 388 Chapter 13 Basic Router Configuration and Operation Example 13 9 IP Naming Configuration and show host Command Continued Cooperstown show hosts Default domain is gileadoundation org Name address lookup uses static mappings Host Flags Age Type Address es Mays perm OK 0 IP 10 1 1 1 Aaron perm OK 0 IP 10 2 2 2 Mantle perm OK 0 IP 10 3 3 3 Cooperstown Router Cooperstown will use any of the three statically configured host name to IP address mappings Three names are configured statically in this case Mays Aaron and Mantle Any command referring to Mays Aaron or Mantle will resolve into the IP addresses shown in the ip host command Router Cooperstown also will ask a DNS for name resolution if it does not know the name and IP address already The DNS configuration is shown toward the end of the configuration The IP add
260. ur wire circuit as seen in this chapter Describe the role of the devices in relation to clocking and synchronization Answer The routers receive clocking from their respective CSU DSUs One of the two CSU DSUs is configured as the master The other CSU DSU as the slave adjusts its clock to match the speed of the master CSU DSU 11 Imagine a drawing with two routers each connected to an external CSU DSU which each is connected with a four wire circuit as seen in this chapter List the words behind the acronyms DTE and DCE and describe which devices in this imagined network are DTE and which are DCE Answer DTE stands for data terminal equipment and DCE stands for data communications equipment The routers are DTEs and the CSU DSUs are DCEs 12 Imagine a drawing with two routers each connected to a Frame Relay switch over a local access link Describe which devices in this imagined network are Frame Relay DTEs and which are Frame Relay DCEs Answer The routers are DTEs and the Frame Relay switches are DCEs Chapter5 509 13 Do HDLC and PPP as implemented by Cisco routers support protocol type fields and error detection Explain your answer Answer Both protocols support a protocol type field and an FCS field to perform error detection PPP has both fields based on the protocol specification Cisco added the protocol type field to the standard HDLC header 14 Imagine a point to point leased line between two rout
261. uspend The telnet IOS exec command enables you to Telnet from one Cisco device to another in practical use it is typically to another Cisco device One of the most important features of the telnet command is the suspend feature To understand the suspend function you should to refer to the network diagram in Figure 13 4 Bench Figure 13 4 Telnet Suspension SO 2 Cincy Frame peers Milwaukee ss z s New York 1 1_ CI CI o In the figure the router administrator is using Bench to Telnet into the Cincy router When in Cincy the user Telnets to Milwaukee When in Milwaukee the user suspends the Telnet by pressing Ctrl Shift 6 followed by pressing the letter x The user then Telnets to New York and again suspends the connection The example begins with Bench already logged into Cincy Example 13 10 shows example output with annotations to the side Uecker Example 13 10 Telnet Suspensions Cincy telnet milwaukee User issues command to Telnet to Milwaukee Trying Milwaukee 10 1 4 252 Open User Access Verification Password User plugs in password can type commands at Milwaukee continues 390 Chapter 13 Basic Router Configuration and Operation Example 13 10 Telnet Suspensions Continued Milwaukee gt Milwaukee gt Milwaukee gt Note User pressed Ctrl Shift 6 and then x Cincy telnet NewYork User back at Cincy because Telnet was suspended Trying NewYork 10 1 6 253
262. utes in network and build routing tables 28 True or false Routing protocols are required to learn routes of directly connected subnets Answer False Routers add routes to directly connected subnets when the interfaces initialize No routing protocols are needed 29 Which IP routing protocols are Cisco proprietary Answer IGRP and EIGRP 30 Chapter6 515 List the similarities and differences between RARP and BOOTP Answer Both protocols send broadcasts looking for a server and they hope to have the server assign them an IP address BOOTP also can be used to assign other parameters such as the subnet mask default gateway DNS address and filenames for downloading an operating system 31 List the similarities and differences between DHCP and BOOTP Answer Both protocols send broadcasts looking for a server and they hope to have the server assign them an IP address Both can be used to assign a large variety of parameters such as the subnet mask default gateway DNS address and filenames for downloading an operating system DHCP does not require that the server be preconfigured with the MAC addresses of all the DHCP client PCs making it much more scalable 32 List the similarities and differences between ARP and DNS Answer Both protocols send messages with one bit of information hoping to learn another bit of information The similarities do not go beyond that fact DNS requests are unicast IP packets sent specif
263. uting table with a route to all subnets in the network m If more than one route to a subnet is available to place the best route in the routing table m To notice when routes in the table are no longer valid and to remove those routes from the routing table m Ifa route is removed from the routing table and another route through another neighboring router is available to add the route to the routing table Many people view this goal and the preceding one as a single goal m To add new routes or to replace lost routes with the best currently available route as quickly as possible The time between losing the route and finding a working replacement route is called convergence time m To prevent routing loops So all routing protocols have the same general goals Cisco IOS Software supports a large variety of IP routing protocols IP s long history and continued popularity have resulted in the specification and creation of several different competing routing protocol options So classifying IP routing protocols based on their differences is useful Comparing and Contrasting IP Routing Protocols Routing protocols can be categorized in several ways One distinction is whether the protocol is more useful between two companies or inside a single company Only one IP routing protocol that is popular today the Border Gateway Protocol BGP is designed specifically for use between two different organizations In fact BGP distributes routing
264. ved for a typical user Answer Two switch ports are used which reduces the possibility of collisions Also each segment has its own 10 or 100 Mbps capacity allowing more throughput and reducing the likelihood of collisions Furthermore some Cisco switches can reduce the flow of multicasts using the Cisco Group Message Protocol CGMP and IGMP snooping 532 Appendix A Answers to the Do Know This Already Quizzes and O amp A Sections 12 How fast is Fast Ethernet Answer 100 million bits per second 100 Mbps 13 How does a transparent bridge build its address table Answer The bridge listens for incoming frames and examines the source MAC address If it is not in the table the source address is added along with the port interface by which the frame entered the bridge The bridge also marks an entry for freshness so that entries can be removed after a period of disuse This reduces table size and allows for easier table changes in case a spanning tree change forces more significant changes in the bridge address table 14 How many bytes long is a MAC address Answer 6 bytes long or 48 bits 15 Does a bridge or switch examine just the incoming frame s source MAC the destination MAC or both Why does it examine the one s that it examines Answer The bridge or switch examines both MAC addresses The source is examined so that entries can be added to the bridge address table The destination address is exami
265. ver ICMP is actually an integral part of IP and must be implemented by every IP module ICMP uses messages to accomplish its tasks Many of these messages are used in even the smallest IP network Table 13 4 lists several ICMP messages 382 Chapter 13 Basic Router Configuration and Operation Table 13 4 ICMP Message Types Message Purpose Destination unreachable _ This tells the source host that there is a problem delivering a packet Time exceeded The time that it takes a packet to be delivered has expired the packet has been discarded Redirect The router sending this message has received some packet for which another router would have had a better route the message tells the sender to use the better route Echo This is used by the ping command to verify connectivity ICMP Echo Request and Echo Reply The ICMP echo request and echo reply messages are sent and received by the ping command In fact when people say that they sent a ping packet they really mean that they sent an ICMP echo request These two messages are very self explanatory The echo request simply means that the host to which it is addressed should reply to the packet The echo reply is the ICMP message type that should be used in the reply The echo request includes some data that can be specified by the ping command whatever data is sent in the echo request is sent back in the echo reply Example 13 8 shows two ping commands
266. would not ask such trivia on the test 16 What is the intended purpose of RAM in a Cisco router Answer RAM is used as IOS working memory storing such things as routing tables or packets and for IOS code storage In some router models not all IOS is copied into RAM Some of IOS is left in Flash memory so that more RAM is available for working memory It also holds the currently in use configuration file called running config 17 What is the main purpose of ROM in a Cisco router Answer To store a small limited function version of IOS and to store bootstrap code Typically this type of IOS is used only during maintenance or emergencies 18 What configuration command would be needed to cause a router to use an IOS image named c2500 j 1 112 14 bin on TFTP server 128 1 1 1 when the router is reloaded If you forgot the first parameter of this command what steps must you take to learn the correct parameters and add the command to the configuration Assume that you are not logged in to the router when you start boot system tftp c2500 j 1 112 14 bin 128 1 1 1 Answer As for the second part of the question Log in from con aux telnet type the enable command type the enable password type the configure terminal command and type boot Help appears for the first parameter of the boot command 19 What command sets the password that would be required after typing the enable command Is that password encrypted by default Answer
267. y the microprocessor routed protocol A protocol that can be routed by a router A router must be capable of interpreting the logical internetwork as specified by that routed protocol Examples of routed protocols include AppleTalk DECnet and IP routing protocol A protocol that accomplishes routing through the implementation of a specific routing algorithm Examples of routing protocols include the Interior Gateway Routing Protocol IGRP the Open Shortest Path First OSPF protocol and the Routing Information Protocol RIP segment A term used in the TCP specification to describe a single transport layer unit of information Can instead be called an L4 PDU segmentation The process of breaking a large piece of data from an application into pieces appropriate in size to be sent through the network single mode A type of fiber optic cabling with a narrow core that allows light to enter only at a single angle Such cabling has a higher bandwidth than multimode fiber but requires a light source with a narrow spectral width such as a laser 588 socket socket A software structure operating as a communications endpoint within a network device SONET Synchronous Optical Network A standard format for transporting a wide range of digital telecommunications services over optical fiber SONET is characterized by standard line rates optical interfaces and signal formats SONET is a high speed up to 2 5 Gbps synchronous network specifi

a. no shutdown b. shutdown c. enable e. no

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