Troubleshooting IP Connectivity
Contents
1. e show access lists e show interfaces Global Knowledge Training LLC L6 15 Lab 6 Troubleshooting IP Connectivity e show ip interfaces e show ip route e ping destination e telnet destination e trace destination Note Do not pass this point until you have verified that the configuration issues have been corrected Save the configurations 30 Save all of your pod devices running configs to NVRAM PxRl copy running config startup config PxR2 copy running config startup config PxSWHcopy running config startup config Lab Complete L6 16 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity Completed Configuration The resulting router and switch configurations for this lab are the same as the previous lab PCI and PC2 now have Server in their local hosts file Global Knowledge Training LLC L6 17 Lab 6 Troubleshooting IP Connectivity L6 18 Global Knowledge Training LLC2. doubts reset to this lab as described in Lab 0 Introduction and Connecting to and Using the Remote Lab Environment Note The Appendix Troubleshooting Scenarios provides information about each of the troubleshooting files refer to this appendix if you need assistance during this lab Verify initial configuration 1 Connect to your PxR1 Ping from your PxR1 to the TFTP server 172 16 1 1 The ping should be successful If not troubleshoot your configurations PxR1l ping 172 16 1 1 Type escape sequence to abort Sending 5 100 byte ICMP Echos to 172 16 1 1 timeout is 2 seconds Success rate is 100 percent 5 5 round trip min avg max 1 1 4 ms PxR1 2 Connect to your PxR2 Ping from your PxR2 to the TFTP server 172 16 1 1 The ping should be successful If not troubleshoot your configurations PxR2 ping 172 16 1 1 Type escape sequence to abort Sending 5 100 byte ICMP Echos to 172 16 1 1 timeout is 2 seconds Success rate is 80 percent 4 5 round trip min avg max 1 1 4 ms PxR2 3 From PxR2 trace to the TFTP server 172 16 1 1 PxR2 traceroute 172 16 1 1 Type escape sequence to abort Tracing the route to 172 16 1 1 VRF info vrf in name id vrf out name id 1 10 3 x 1 0 msec 0 msec 4 msec 2 192 168 xx 3 0 msec 0 msec 0 msec 3 172 16 1 1 0 msec 0 msec 0 msec PxR2 Global Knowledge Training LLC L6 5 Lab 6 Troubleshooting IP Connectivity The trace should be successful The packet
3. it doesn t work giving you no idea where to start Therefore instead of show run we might approach things by using some commands in an attempt to localize the problem In this first IP connectivity troubleshooting exercise you ll be led by the hand to get a feel for the process 16 As an aid to troubleshooting ask yourself the following questions 16 1 Did it ever work 16 2 Was anything changed 16 3 What are the symptoms 16 4 What could reasonably cause these symptoms Global Knowledge Training LLC L6 11 Lab 6 Troubleshooting IP Connectivity 17 In this case the ping was unsuccessful From the dots in the output you can see that the ping timed out The following table describes meanings of the possible output characters from ping Character Description Reply received Timeout while waiting for a reply U Destination unreachable error PDU was received Q Source quench M Could not fragment Unknown packet type amp Packet lifetime exceeded I User interrupted test 18 Let s test a couple of other things From the switch trace to the TFTP server 172 16 1 1 PxSWHtraceroute 172 16 1 1 Type escape sequence to abort Tracing the route to router 172 16 1 1 1 2 3 4 PxSW Note You can interrupt the traceroute by using the escape sequence which is the Ctrl or Ctrl Shift 6 key sequence 19 The traceroute
4. 1 bytes 32 time ims TTL 62 Ping statistics for 172 16 1 1 Packets Sent 4 Received 4 Lost z loss Approximate round trip times in milli seconds Minimum ims Maximum ims Average ims C Users adom gt _ L6 6 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity Troubleshoot PC issue In this section you will troubleshoot an issue on PCI and PC2 There is no DNS server in the lab network so if users on the PCs want to use names instead of addresses they will have to use local name mapping 6 Ping from your PCI and PC2 to the name Server The pings should not be successful Here s one of the PCs pinging Server C Users adom gt ping Server Ping request could not find host Server Please check the name and try again C Users adom gt _ 7 On PCI and PC2 do the following From the Start menu choose All Programs gt Windows Accessories Right click on Notepad and chose Run as administrator amp Internet Explorer 3CDaemon Administrative Tools D HiliSoft MIB Browser P Maintenance P Scrutinizer NetFlow amp sFlow Analyzer d StartMenu8 d Startup B VMuvare di Windows Accessories fal Calculator A Math Input Panel Notepad GX Paint Open HS Remote Open file location Q Snippin Pin to Start Sound Runas administrator ime Steps R Pin to Taskbar Sticky N D System Ji Tablet Cut Send to A WordP4 Copy az
5. 4 Back Create shortcut Delete Search progra Properties Global Knowledge Training LLC Favorites Computer Network Control Panel Default Progra Switch to Metre L6 7 Lab 6 Troubleshooting IP Connectivity 8 Within the Notepad application click on File gt Open and browse to the C Windows System32 Drivers etc directory In the dropdown menu on the lower right side of the Open dialog box select All Files You should see some files listed including the hosts file Untitled Notepad Oo File Edit Format View Help gt T Local Disk C Windows Systemm32 Drivers gt etc Organize New folder B A wr Favorites Name Date modified Type E Desktop L hosts 7 26 2012 12 17 AM File M Downloads _ Imhosts sam 7 26 2012 2 52 AM SAM File E Recent places _ networks 7 26 2012 12 17 AM File _ protocol 7 26 2012 12 17AM File C3 Libraries services 7 26 2012 12 17AM File L Documents Music Pictures E videos 2 Computer G Network GS File name Encoding ANSI L6 8 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity 9 Click on the hosts file and then click on the Open button The hosts file contains a mapping of IP addresses to names Enter a mapping of the IP address 172 16 1 1 to the name Server File Edit Format View Help Copyright c 1993 2009 Microsoft Corp 4 This is a sample HOSTS file used by Mi
6. 6 1 1 IP R1 c txt Loading IP R1 c txt from 172 16 1 1 via GigabitEthernet0 1 OK 257 bytes 257 bytes copied in 2 028 secs 127 bytes sec PxR1 28 Perform some tests to determine what the symptoms of the problem are The following are some suggested tests and expected results Make sure that you use the correct target addresses passwords and file names Test Expected Your Result Result Ping from PC1 or PC2 to TFTP server 172 16 1 1 Yes Telnet from PC1 or PC2 to core router 192 168 xx 3 No Ping from PxSW to TFTP server 172 16 1 1 Yes Trace from PxSW to TFTP server 172 16 1 1 Yes Telnet from PxSW to core router 192 168 xx 3 Yes Ping from PxR1 to TFTP server 172 16 1 1 Yes Copy the file tftp txt from the TFTP server 172 16 1 1 to Yes PxR1 or PxSW running config Note that the tftp txt file just contains comments it will not change the configuration when it is merged into the running config Ping from PxR2 to TFTP server 172 16 1 1 Yes Trace from PxR2 to TFTP server 172 16 1 1 Yes Note Recall that PxR1 is configured with an ACL to deny PC1 and PC2 from being able to telnet to the core router 29 If your results don t match the expected results you have some troubleshooting to do After you fix the problem run the tests again to verify the results You may find these commands helpful e copy tftp running config using the tftp txt file
7. Global Knowledge Training LLC E column followed by the corresponding host name L6 9 Lab 6 Troubleshooting IP Connectivity 11 Ping from your PCI and PC2 to the name Server again The pings should be successful Here s one of the PCs pinging Server C Users adom gt ping Server Pinging Server 172 16 1 1 with 32 bytes of data Reply from 16 2 6 1 Destination net unreachable Reply from 18 2 6 1 Destination net unreachable Reply from 16 2 6 1 Destination net unreachable Reply from 18 2 6 1 Destination net unreachable Ping statistics for 172 16 1 1 Packets Sent 4 Received 4 loss C Users adom gt _ This time the ping was successful Troubleshoot PxSW issue In this section you will troubleshoot an issue on PxSW by downloading a file into its running config 12 Download the file IP SW a txt from the TFTP server 172 16 1 1 into PxSW s running config don t forget the suffix of txt PxSWHcopy tftp run Address or name of remote host 172 16 1 1 Source filename IP SW a txt Destination filename running config Accessing tftp 172 16 1 1 IP SW a txt Loading IP SW a txt from 172 16 1 1 via Vlani OK 223 bytes 223 bytes copied in 8 044 secs 28 bytes sec PxSWH If the copy was successful you will receive the OK followed by the file size and some statistics regarding the time and transfer rate If the copy was unsuccessful you will se
8. L6 Troubleshooting IP Connectivity Global Knowledge Training LLC L6 1 Lab 6 Troubleshooting IP Connectivity Objectives In this lab you will first diagnose and correct an IP connectivity issue on PCI and PC2 You will then download a config file into PxSW to introduce an IP connectivity problem within your pod which you will then diagnose and correct You will download a config file into PxR2 to introduce IP connectivity problems within your pod which you will then diagnose and correct You will repeat the process with a file loaded into PxR1 L6 2 The objectives for this lab are Diagnose and correct an IP connectivity issue on PCI and PC2 Load a configuration file into PxSW that causes IP connectivity problems diagnose and correct the problem Load a configuration file into PxR2 that causes IP connectivity problems diagnose and correct the problem Load a configuration file into PxR1 that causes IP connectivity problems diagnose and correct the problem Important Substitute your pod number for x and the router number for y in all instructions and commands The passwords configured on the devices at this point are Console and vty access username cena password cisco enable secret sanfran Global Knowledge Training LLC Lab Topology Lab 6 Troubleshooting IP Connectivity The following diagram illustrates the logical topology used in this lab along with the IP addresses configured Comman
9. bout interfaces show ip route Displays the IP routing table show running config include Displays the portions of the running expression configuration that include the specified expression config if no shutdown Without the no keyword enables the interface With the no keyword disables the interface telnet address Establishes a Telnet connection to the specified IP address The telnet keyword can be omitted just entering an IP address will open a Telnet connection traceroute address Traces the route that packets take to the specified address Windows Commands Used In This Lab Command Description ping address Causes an ICMP echo message to be sent to the destination which should cause an ICMP echo reply message to be returned tracert address Traces the route that packets take to the specified address L6 4 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity Procedure In this lab you will first diagnose and correct an IP connectivity issue on PCI and PC2 You will then download a config file into PxSW to introduce an IP connectivity problem within your pod which you will then diagnose and correct You will download a config file into PxR2 to introduce IP connectivity problems within your pod which you will then diagnose and correct You will repeat the process with a file loaded into PxR1 Note This lab requires that the previous lab was completed correctly If you have any
10. crosoft TCP IP for Windows This file contains the mappings of IP addresses to host names Each entry should be kept on an individual line The IP address should be placed in the first column followed by the corresponding host name The IP address and the host name should be separated by at least one space Additionally comments such as these may be inserted on individual lines or following the machine name denoted by a symbol For example 162 54 94 97 rhino acme com source server 38 25 63 16 x acme com x client host localhost name resolution is handled within DNS itself 1278 80 21 localhost ned localhost 172 16 1 1 Server 10 Save the file and exit from notepad File Edit Format View Help New Ctrl N 39 Microsoft Corp Open R Ctrl 0 Save Ctrl S Save As 5 file used by Microsoft TCP IP for Windows mappings of IP addresses to host names Each Page Setup pn an individual line The IP address should us CiP L host name should be separated by at least one Exit Additionally comments such as these may be inserted on individual lines or following the machine name denoted by a symbol For example 102 54 94 97 rhino acme com source server 38 25 63 19 X acme com x client host Ei localhost name resolution is handled within DNS itself 127 6 0 1 localhost real localhost 72 16 1 1 Server be Ft dt tt
11. d List 192 168 xx 1 24 Gi0 1 The following table lists the commands used in this lab in alphabetical order Command clear ip arp address Cisco IOS Commands Used In This Lab Description Clears the specified entry in the ARP cache ona switch configure terminal Enters global configuration mode copy running config startup config Saves the running config to NVRAM copy tftp running config Copies a file from TFTP server to running config gt enable Enters the EXEC privileged mode config end Terminates configuration mode exit Exit the current mode and go up one level config interface type number Enters configuration mode for the interface config ip access list type name Global Knowledge Training LLC Enters configuration mode for a named ACL L6 3 Lab 6 Troubleshooting IP Connectivity config ip default gateway Configures the specified IP address as the address default gateway for the switch config ext nacl no permit Creates an entry within a named ACL With the deny condition no parameter deletes the entry ping address Sends an echo request to the specified address show access lists Displays ACLs show interfaces type number Displays info about interfaces show interfaces type number Displays trunking info about an interface trunk show ip interfaces Displays IP info a
12. e a message similar to this Error opening tftp 172 16 1 1 IP SW a txt cause of error condition If an error message occurs troubleshoot your configuration and then retry the download Note Do not pass this point until you have successfully downloaded the problem file from the TFTP server into PxSW s running config L6 10 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity Examine connectivity 13 Clear PxSW s IP ARP entry for the TFTP server 172 16 1 1 PxSWHclear ip arp 172 16 1 1 14 Attempt to ping from your PxSW to the TFTP server 172 16 1 1 The ping should be successful If not you have a problem to solve PxSWHping 172 16 1 1 Type escape sequence to abort Sending 5 100 byte ICMP Echos to 172 16 1 1 timeout is 2 seconds Success rate is 0 percent 0 5 PxSW In this case the ping does not work Diagnose the problem 15 In this case because of the TFTP transfer we know that the problem is with PxSW s running config Because the running config is relatively small two pages or so a reasonable approach to troubleshooting might be to simply view the running config show run and look for problems This approach is not scalable in general because in the real world the problem usually isn t caused by downloading a file for the specific purpose of breaking the config Instead you could be faced with configs that are ten or more pages long and a trouble ticket that says
13. ormation about each of the troubleshooting files If after a few minutes you cannot discover the problem we suggest looking at this appendix for assistance 27 Download the IP PxR2 b txt substituting x with your pod number problem file into PxR2 s running config then troubleshoot and correct the problem When you have corrected that problem you can download the IP R1 c txt problem file into PxRl s running config then troubleshoot and correct that problem Only download one file at a time When downloading don t forget the txt suffix Here is an example of downloading the file for the example Pod 6 into P6R2 P6R2 copy tftp run Address or name of remote host 172 16 1 1 Source filename IP P6R2 b txt Destination filename running config Accessing tftp 172 16 1 1 IP P6R2 b txt Loading IP P6R2 b txt from 172 16 1 1 via GigabitEthernet0 0 OK 234 bytes 234 bytes copied in 2 024 secs 116 bytes sec P6R2 Important Make sure you are downloading into the correct device and substitute your pod number for x in the file name L6 14 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity Here is an example of downloading the file for PxR1 remember to only do this after you have corrected the problem in PxR2 PxRl copy tftp run Address or name of remote host 172 16 1 1 Source filename IP Rl c txt Destination filename running config Accessing tftp 172 1
14. s should take the path via PxR1 10 3 x 1 to the core router 192 168 xx 3 and then to the TFTP server If not troubleshoot your configurations 4 Connect to your PxSW Ping from your PxSW to the TFTP server 172 16 1 1 The ping should be successful If not troubleshoot your configurations PxSWHping 172 16 1 1 Type escape sequence to abort Sending 5 100 byte ICMP Echos to 172 16 1 1 timeout is 2 seconds Success rate is 100 percent 5 5 round trip min avg max 1 4 9 ms PxSW 5 Connect to your PCI and PC2 Ping from your PCI and PC2 to the TFTP server 172 16 1 1 The pings should be successful If not troubleshoot your configurations Here s PCI pinging the TFTP server C Users adom gt ping 172 16 1 1 Pinging 172 16 1 1 with 32 bytes of data Reply from 172 16 1 1 bytes 32 time 4ms TTL 62 Reply from 172 16 1 1 bytes 32 time 3ms TTL 62 Reply from 172 16 1 1 bytes 32 time ims TTL 62 Reply from 172 16 1 1 bytes 32 time ims TTL 62 Ping statistics for 172 16 1 1 Packets Sent 4 Received 4 Lost z loss Approximate round trip times in milli seconds Minimum ims Maximum 4ms Average 2ms C Users adom gt _ Here s PC2 pinging the TFTP server C Users adom gt ping 172 16 1 1 Pinging 172 16 1 1 with 32 bytes of data Reply from 172 16 1 1 bytes 32 time ims TTL 62 Reply from 172 16 1 1 bytes 32 time ims TTL 62 Reply from 172 16 1 1 bytes 32 time ims TTL 62 Reply from 172 16 1
15. should be successful but it s not From the s in the output you can see that the probe timed out The following table describes meanings of the possible output characters from traceroute Character Description nn msec For each node the round trip time in milliseconds for the specified number of probes The probe timed out Unknown packet type A Administratively unreachable Usually this output indicates that an access list is blocking traffic H Host unreachable Network unreachable P Protocol unreachable L6 12 Global Knowledge Training LLC Lab 6 Troubleshooting IP Connectivity Q Source quench U Port unreachable User interrupted test 20 Since the ping and traceroute are timing out it appears that PxSW is not getting to a router Recall that PxR1 is the default gateway and it is on the switch s FastEthernet 0 1 interface Confirm that the interface is up PxSW show interfaces fa0 1 FastEthernet0 1 is up line protocol is up connected Hardware is Fast Ethernet address is 2401 c70f 4d81 bia 2401 c70f 4d81 The interface is up up 21 Confirm that the FastEthernet 0 1 interface is trunking PxSW show interface fa0 1 trunk Port Mode Encapsulation Status Native vlan Fa0 1 on 802 1q trunking 1 Port Vlans allowed on trunk Fa0 1 1 1x 2x 3x Port Vlans allowed and active in management domain Fa0 1 1 1x 2x 3x Port Vlans in spanning tree forwarding sta
16. te and not pruned Fa0 1 1 1x 2x 3x The interface is trunking 22 Since the interface is ok check the line in the running configuration that defines the switch s default gateway PxSW show run include ip default gateway ip default gateway 10 10 7 1 The IP default gateway should be 10 10 x 1 but it is not Correct the problem 23 To correct the problem put the correct default gateway back on PxSW PxSW configure terminal PxSW config ip default gateway 10 10 x 1 PxSW config end 24 Check the line in the running configuration that defines the switch s default gateway PxSWH show run include ip default gateway ip default gateway 10 10 x 1 The IP default gateway is now correct Global Knowledge Training LLC L6 13 Lab 6 Troubleshooting IP Connectivity Verify connectivity 25 Attempt to ping from your PxSW to the TFTP server 172 16 1 1 The ping should be successful PxSW ping 172 16 1 1 This time the ping does work Download additional problem files to PxR2 and to PxR1 26 There are additional IP connectivity problem files The first file is to download to PxR2 and the second file is to download into PxR1 they are not for PxSW e JP PxR2 b txt where x is your pod number For example if you are on pod 5 use the file IP P5R2 b txt e IP Rl c txt Important You may not have time to do all of the troubleshooting files in class Important The Appendix Troubleshooting Scenarios provides inf
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