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Cisco Systems BC-109 User's Manual

1. Command Purpose netbios access list host name permit deny pattern Assign the name of an access list to a station or set of stations on the network When filtering by station name you can choose to filter either incoming or outgoing messages on the interface To specify the direction use one of the following commands in interface configuration mode Command Purpose netbios input access filter host name Define an access list filter for incoming messages netbios output access filter host name Define an access list filter for outgoing messages Configure NetBIOS Access Filters Using a Byte Offset BC 134 To configure access filters you must do the following Step 1 Assign a byte offset access list name Step 2 Specify the direction of the message to be filtered on the interface Keep the following notes in mind while configuring access filters using a byte offset When an access list entry has an offset plus the length of the pattern that is larger than the packet s length the entry will not make a match for that packet Because these access lists allow arbitrary byte offsets into packets these access filters can have a significant impact on the amount of packets per second transiting across the bridge They should be used only when situations absolutely dictate their use The NetBIOS byte offset access list contains a series of offsets and hexadecimal patterns with which to match byte offsets in Ne
2. In addition to the EXEC mode commands to maintain the SRB network you can use the following command in global configuration mode Command Purpose source bridge tcp queue max number Limit the size of the backup queue for RSRB to control the number of packets that can wait for transmission to a remote ring before they start being thrown away SRB Configuration Examples The following sections provide SRB configuration examples Basic SRB with Spanning Tree Explorers Example SRB with Automatic Spanning Tree Function Configuration Example Optimized Explorer Processing Configuration Example SRB Only Example SRB and Routing Certain Protocols Example Multiport SRB Example SRB with Multiple Virtual Ring Groups Example SRB over FDDI Configuration Examples SRB over FDDI Fast Switching Example SRB over Frame Relay Configuration Example Adding a Static RIF Cache Entry Example Adding a Static RIF Cache Entry for a Two Hop Path Example SR TLB for a Simple Network Example SR TLB with Access Filtering Example Configuring Source Route Bridging BC 145 SRB Configuration Examples NetBIOS Support with a Static NetBIOS Cache Entry Example LNM for a Simple Network Example LNM for a More Complex Network Example NetBIOS Access Filters Example Filtering Bridged Token Ring Packets to IBM Machines Example Administrative Access Filters Filtering SNAP Frames on Output Example Creati
3. Command Purpose mac address iece address Reset the MAC address of the Token Ring interface to a value that provides a workaround to a problem in Texas Instruments Token Ring MAC firmware Configuring Source Route Bridging BC 143 Monitor and Maintain the SRB Network Report Spurious Frame Copied Errors An IBM 3174 cluster controller can be configured to report frame copied errors to IBM LAN Network Manager software These errors indicate that another host is responding to the MAC address of the 3174 cluster controller Both the 3174 cluster controller and the IBM LAN Network Manager software can be configured to ignore frame copied errors Monitor and Maintain the SRB Network You can display a variety of information about the SRB network To display the information you require use one or more of the following commands in EXEC mode Command Purpose show access expression begin exclude include Display the defined input and output access list expressions show controllers token Display internal state information about the Token Ring interfaces in the system show interfaces token Provide high level statistics for a particular interface show interfaces Provide high level statistics about the state of source bridging for a particular interface show Inm bridge Display all currently configured bridges and all parameters that are related to the bridge as a whole and not to o
4. Command Purpose Inm disabled Disable LNM functionality Configuring Source Route Bridging BC 129 Configure LNM Support The command can be used to terminate all LNM server input and reporting links In normal circumstances this command should not be necessary because it is a superset of the functions normally performed on individual interfaces by the no Inm rem and no Inm rps commands Disable Automatic Report Path Trace Function Under some circumstances such as when new hardware has been introduced into the network and is causing problems the automatic report path trace function can be disabled The new hardware may be setting bit fields B1 or B2 or both of the routing control field in the routing information field embedded in a source route bridged frame This condition may cause the network to be flooded by report path trace frames if the condition is persistent The Inm pathtrace disabled command along with its options allows you to alleviate network congestion that may be occurring by disabling all or part of the automatic report path trace function within LNM To disable the automatic report path trace function use the following command in global configuration mode Command Purpose Inm pathtrace disabled all origin Disable LNM automatic report path trace function Prevent LNM Stations from Modifying Cisco IOS Software Parameters Because there is now more than one way to remotely change parameters in a ro
5. Configuring Source Route Bridging This chapter describes source route bridging SRB configuration tasks For a discussion of remote source route bridging RSRB configuration tasks refer to the Configuring Remote Source Route Bridging chapter in this publication For a complete description of the SRB commands mentioned in this chapter refer to the Source Route Bridging Commands chapter in the Bridging and IBM Networking Command Reference To locate documentation of other commands that appear in this chapter use the command reference master index or search online SRB Configuration Task List Perform the tasks in the following sections to configure SRB Configure Source Route Bridging Configure Bridging of Routed Protocols Configure Translation between SRB and Transparent Bridging Environments Configure NetBIOS Support Configure LNM Support Secure the SRB Network Tune the SRB Network Establish SRB Interoperability with Specific Token Ring Implementations Monitor and Maintain the SRB Network See the end of this chapter for SRB Configuration Examples Warning The Cisco IOS software issues a warning if a duplicate bridge definition exists in a router You must remove an old bridge definition before adding a new bridge definition to a router configuration Configuring Source Route Bridging BC 109 Configure Source Route Bridging Configure Source Route Bridging Our implementa
6. Ring T1 Token T2 i o E TO Token Ring t Ring T3 Token Ring To configure multiple dual port source route bridges use the following command in interface configuration mode for each Token Ring interface that is part of a dual port bridge 2323 Command Purpose source bridge local ring bridge number target ring Enable local source route bridging on a Token Ring interface If you want your network to use only SRB you can connect as many routers as you need via Token Rings Remember source route bridging requires you to bridge only Token Ring media Configure a Multiport Bridge Using a Virtual Ring A better solution for overcoming the two ring number limitation of IBM Token Ring chips is to configure a multiport bridge using a virtual ring A virtual ring on a multiport bridge allows the router to interconnect three or more LANs with any to any connectivity that is connectivity between any of the routers on each of the three LANs is allowed A virtual ring creates a logical Token Ring internal to the Cisco IOS software which causes all the Token Rings connected to the router to be treated as if they are all on the same Token Ring The virtual ring is called a ring group Figure 47 shows a multiport bridge using a virtual ring Configuring Source Route Bridging BC 111 Configure Source Route Bridging Figure 47 Multiport Bridge Using a Virtual Ring To take advantage of this virtual ring feature each Token Ri
7. netbios name cache name len length Specify the number of characters of the NetBIOS type name to cache Enable NetBIOS Proxying The Cisco IOS software can act as a proxy and send NetBIOS datagram type frames To enable this capability use the following global configuration command Command Purpose netbios name cache proxy datagram seconds Enable NetBIOS proxying To define the validation time when the software is acting as a proxy for NetBIOS NAME_QUERY command or for explorer frames use the following global configuration command Command Purpose rif validate age seconds Define validation time Create Static Entries in the NetBIOS Name Cache If the router communicates with one or more NetBIOS stations on a regular basis adding static entries to the NetBIOS name cache for these stations can reduce network traffic and overhead You can define a static NetBIOS name cache entry that associates the server with the NetBIOS name and the MAC address If the router acts as a NetBIOS server you can specify that the static NetBIOS name cache is available locally through a particular interface If a remote router acts as the NetBIOS server you can specify that the NetBIOS name cache is available remotely To do this use one of the following commands in global configuration mode Command Purpose netbios name cache mac address netbios name Define a static NetBIOS name cache entry interface name and specify that it is a
8. Function Prevent LNM Stations from Modifying Cisco IOS Software Parameters Enable Other LRMs to Change Router Parameters Apply a Password to an LNM Reporting Link Enable LNM Servers Change Reporting Thresholds Change an LNM Reporting Interval Enable the RPS Express Buffer Function Monitor LNM Operation Configure LNM Software on the Management Stations to Communicate with the Router Because configuring an LNM station is a fairly simple task and is well covered in the LNM documentation it is not covered in depth here However it is important to mention that you must enter the MAC addresses of the interfaces comprising the ports of the bridges as adapter addresses When you configure the router as a multiport bridge configuring an LNM station is complicated by the virtual ring that is involved The basic problem extends from the fact that LNM is designed to only understand the concept of a two port bridge and the router with a virtual ring is a multiport bridge The solution is to configure a virtual ring into the LNM Manager station as a series of dual port bridges Disable LNM Functionality Under some circumstances you can disable all LNM server functions on the router without having to determine whether to disable a specific server such as the ring parameter server or the ring error monitor on a given interface To disable LNM functionality use the following command in global configuration mode
9. NetBIOS access filters administrative filters and access expressions that can be combined with administrative filters In addition these features can be used to increase network performance because they reduce the number of packets that traverse the backbone network Configure NetBIOS Access Filters NetBIOS packets can be filtered when transmitted across a Token Ring bridge Two types of filters can be configured Host access list Used for source and destination station names Byte offset access list Used for arbitrary byte patterns in the packet itself As you configure NetBIOS access filters keep the following issues in mind The access lists that apply filters to an interface are scanned in the order they are entered There is no way to put a new access list entry in the middle of an access list All new additions to existing NetBIOS access lists are placed at the end of the existing list Access list arguments are case sensitive The software makes a literal translation so that a lowercase a is different from an uppercase A Most nodes are named in uppercase letters A host NetBIOS access list and byte NetBIOS access list can each use the same name The two lists are identified as unique and bear no relationship to each other The station names included in the access lists are compared with the source name field for NetBIOS commands 00 and 01 ADD_GROUP_NAME_QUERY and ADD_NAME_ QUERY as well as th
10. TLB the two Token Ring interfaces were communicating with two port local source route bridging after SR TLB these two interfaces must be reconfigured to communicate through a virtual ring as follows source bridge ring group 10 interface tokenring 0 source bridge 1 1 10 I interface tokenring 1 source bridge 2 1 10 interface ethernet 0 bridge group 1 1 interface ethernet 1 bridge group 1 1 bridge 1 protocol dec Now you are ready to determine two things A ring number for the pseudo ring that is unique throughout the source route bridged network For the preceding example configuration use the number 3 A bridge number for the path to the pseudo ring For the preceding example configuration use the number 1 BC 154 Bridging and IBM Networking Configuration Guide SR TLB with Access Filtering Example Once you have determined the ring number and the bridge number you can add the source bridge transparent command to the file including these two values as parameters for the command The following partial configuration includes this source bridge transparent entry l source bridge ring group 10 source bridge transparent 10 3 1 1 l interface tokenring 0 source bridge 1 1 10 interface tokenring 1 source bridge 2 1 10 interface ethernet 0 bridge group 1 l interface ethernet 1 bridge group 1 bridge 1 protocol dec SR TLB with Access Filtering Example In the example shown in Figure 63
11. TRUE lsap 201 amp dmac 701 smac 702 Referring to the earlier example An Example Using NetBIOS Access Filters we had the phrase Pass the frame if it is NetBIOS or if it is an SNA frame destined to address 0110 2222 3333 This phrase was converted to the simpler form of Pass if NetBIOS or SNA and destined to 0110 2222 3333 So for the following configuration Access list 201 passes NetBIOS frames command or response access list 201 permit OxFOFO 0x0001 l access list 202 permit 0x0404 0x0001 Permits SNA frames command or response access list 202 permit 0x0004 0x0001 Permits SNA Explorers with NULL DSAP l Access list 701 will permit the FEP MAC address of 0110 2222 3333 access list 701 permit 0110 2222 3333 The following access expression would result access expression in lsap 201 lsap 202 amp dmac 701 Bridging and IBM Networking Configuration Guide Access Filters Example Access Filters Example Figure 69 shows two routers connecting two Token Rings to an FDDI backbone Figure 69 Network Configuration Using NetBIOS Access Filters NetBIOS server NetBIOS clients FILESVR3 r Z n Y Token sg DSDL Z r Ring Router A Router B IBM FEP 3174 3174 1112a address 0110 2222 3333 Suppose you want to permit the IBM 3174 cluster controllers to access the FEP at address 0110 2222 3333 and also want the NetBIOS clients to access the NetBIOS
12. broadcast indicator set in the routing information field Port identifiers consist of ring numbers and bridge numbers associated with the ports The spanning tree algorithm for SRB does not support Topology Change Notification bridge protocol data unit BDPU Note Although the automatic spanning tree function can be configured with source route translational bridging SR TLB the SRB domain and transparent bridging domain have separate spanning trees Each Token Ring interface can belong to only one spanning tree Only one bridge group can run the automatic spanning tree function at a time Configuring Source Route Bridging BC 115 Configure Source Route Bridging To create a bridge group that runs an automatic spanning tree function compatible with the IBM SRB spanning tree implementation use the following command in global configuration mode Command Purpose bridge bridge group protocol ibm Create a bridge group that runs the automatic spanning tree function To enable the automatic spanning tree function for a specified group of bridged interfaces use the following command in interface configuration mode Command Purpose source bridge spanning bridge group Enable the automatic spanning tree function on a group of bridged interfaces To assign a path cost for a specified interface use the following command in interface configuration mode Command Purpose source bridge spanning bridge group path
13. cost path cost Assign a path cost for a specified group of bridged interfaces Note Ports running IEEE and IBM protocols form a spanning tree together on the LAN but they do not mix in the router itself Make sure the configurations are correct and that each LAN runs only one protocol See the end of this chapter for an example of source route bridging with the automatic spanning tree function enabled Limit the Maximum SRB Hops You can minimize explorer storms if you limit the maximum number of source route bridge hops For example if the largest number of hops in the best route between two end stations is six it might be appropriate to limit the maximum source route bridging hops to six to eliminate unnecessary traffic This setting affects spanning tree explorers and all routes explorers sent from source devices To limit the number of SRB hops use one of the following commands in interface configuration mode Command Purpose source bridge max hops count Control the forwarding or blocking of all routes explorer frames received on this interface source bridge max in hops count Control the forwarding or blocking of spanning tree explorer frames received on this interface source bridge max out hops count Control the forwarding or blocking of spanning tree explorer frames sent from this interface Bridging and IBM Networking Configuration Guide Configure Bridging of Routed Protocols Configure Brid
14. different ring groups if for example you plan to administer them as interfaces in separate domains To define or remove a ring group use one of the following commands in global configuration mode Command Purpose source bridge ring group ring group Define a ring group virtual mac address no source bridge ring group ring group Remove a ring group virtual mac address Bridging and IBM Networking Configuration Guide Configure SRB over FDDI Enable SRB and Assign a Ring Group to an Interface After you have defined a ring group you must assign that ring group to those interfaces you plan to include in that ring group An interface can only be assigned to one ring group To enable any to any connectivity among the end stations connected through this multiport bridge you must assign the same target ring number to all Token Ring interfaces on the router To enable SRB and assign a ring group to an interface use the following command in interface configuration mode Command Purpose source bridge local ring bridge number target ring Enable source route bridging and assign a ring group to a Token Ring interface Configure SRB over FDDI Cisco s implementation of SRB expands the basic functionality to allow autonomous switching of SRB network traffic for FDDI interfaces adding counters to SRB accounting statistics and implementing process level switching of SRB over FDDI This functionality provides a
15. it back to LNM In this manner the bridge program becomes a proxy for information about its local Token Ring Without this ability you would require direct access to a device on every Token Ring in the network This process would make managing an SRB environment awkward and cumbersome Figure 51 shows some Token Rings attached through a cloud and one LNM linking to a source route bridge on each local ring Bridging and IBM Networking Configuration Guide Configure LNM Support Figure 51 LNM Linking to a Source Route Bridge on Each Local Ring Token Ring PC running Token Ring If LNM requires information about a station somewhere on a Token Ring it uses a proprietary IBM protocol to query to one of the source route bridges connected to that ring If the bridge can provide the requested information it simply responds directly to LNM If the bridge does not have the necessary information it queries the station using a protocol published in the IEEE 802 5 specification In either case the bridge uses the proprietary protocol to send a valid response back to LNM using the proprietary protocol 1113a As an analogy consider a language translator who sits between a French speaking diplomat and a German speaking diplomat If the French diplomat asks the translator a question in French for the German diplomat and the translator knows the answer he or she simply responds without translating the original question into German If
16. not be included in this statement because the question mark must match some specific character in the name netbios access list host marketing permit W Y The following command illustrates how to combine wildcard characters netbios access list host marketing deny AC The command specifies that the marketing list deny any name beginning with AC that is at least three characters in length the question mark would match any third character The string ACBD and ACB would match but the string AC would not The following command removes the entire marketing NetBIOS access list no netbios access list host marketing To remove single entries from the list use a command such as the following no netbios access list host marketing deny AC This example removes only the list that filters station names with the letters AC at the beginning of the name Configuring Source Route Bridging BC 159 SRB Configuration Examples Access lists are scanned in order In the following example the first list denies all entries beginning with the letters ABC including one named ABCD This voids the second command because the entry permitting a name with ABCD comes after the entry denying it netbios access list host marketing deny ABC netbios access list host marketing permit ABCD Filtering Bridged Token Ring Packets to IBM Machines Example The example in Figure 67 disallows the bridging of Token Ring packets to all IBM workstations on
17. of the following tasks Enable 0x80d5 Processing Enable Standard Token Ring LLC2 to Ethernet LLC2 Conversion Enable 0x80d5 Processing You can change the Cisco IOS software s default translation behavior of translating Token Ring LLC to Ethernet 802 3 LLC to translate Token Ring LLC2 frames into Ethernet 0x80d5 format frames To enable this nonstandard conversion use the following command in global configuration mode Command Purpose source bridge enable 80d5 Change the Ethernet Token Ring translation behavior to translate Token Ring LLC2 frames into Ethernet 0x80d5 format frames Enable Standard Token Ring LLC2 to Ethernet LLC2 Conversion After you change the translation behavior to perform Token Ring LLC2 frames into Ethernet 0x80d5 format frames some of the non IBM hosts in your network topology might use the standard Token Ring conversion of Token Ring LLC2 to 802 3 LLC2 frames If this is the case you can change the translation method of those hosts to use the standard translation method on a per DSAP basis The translation method for all the IBM hosts would still remain as Token Ring LLC2 to Ethernet 0x80d5 translation To define non IBM hosts in your network topology to use the standard translation method while the IBM hosts use the nonstandard method use the following command in global configuration mode Command Purpose source bridge sap 80d5 dsap Allow some other devices to use normal LLC2 IEEE 802 3 t
18. or later To enable NetBIOS name caching you must perform the tasks in the following sections Enable the Proxy Explorers Feature on the Appropriate Interface Specify Timeout and Enable NetBIOS Name Caching In addition you can configure NetBIOS name caching as described in the following sections Configure the NetBIOS Cache Name Length Enable NetBIOS Proxying Configuring Source Route Bridging BC 123 Configure NetBIOS Support Create Static Entries in the NetBIOS Name Cache Specify Dead Time Intervals for NetBIOS Packets Enable the Proxy Explorers Feature on the Appropriate Interface In order to enable NetBIOS name caching on an interface the proxy explorers feature must first be enabled on that interface This feature must either be enabled for response to all explorer packets or for response to NetBIOS packets only To determine whether the proxy explorers feature has been enabled use the following command in EXEC mode Command Purpose show startup config Determine whether or not the proxy explorers feature has been enabled To determine whether proxy explorers has been configured for response to all explorer packets look in the configuration file for the source bridge proxy explorer entry for the appropriate interface For example if the appropriate interface is Token Ring 0 look for an entry similar to the following interface tokenring 0 source bridge proxy explorer If that entry d
19. seconds Specify a dead time interval during which the Cisco IOS software drops any broadcast NetBIOS ADD_NAME_QUERY ADD_GROUP_NAME or STATUS_QUERY frames if they are duplicate frames sent by the same host netbios name cache recognized timeout seconds Specify a dead time interval during which the software drops FIND_NAME and NAME_RECOGNIZED frames if they are duplicate frames sent by the same host Configure LNM Support BC 126 LAN Network Manager LNM formerly called LAN Manager is an IBM product for managing a collection of source route bridges Using either a proprietary protocol or the Simple Network Management Protocol SNMP LNM allows you to monitor the entire collection of Token Rings that comprise your source route bridged network You can use LNM to manage the configuration of source route bridges monitor Token Ring errors and gather information from Token Ring parameter servers Note LNM is supported on the 4 16 Mb Token Ring cards that can be configured for either 4 or 16 Mb transmission speeds LNM support is not provided on CSC R16M cards with SBEMON 2 0 LNM is not limited to managing locally attached Token Ring networks it also can manage any other Token Rings in your source route bridged network that are connected through non Token Ring media To accomplish this task LNM works in conjunction with the IBM Bridge Program The IBM Bridge Program gathers data about the local Token Ring network and relays
20. significant increase in performance for Token Rings interconnected across an FDDI backbone see Figure 48 SRB over FDDI is supported on the Cisco 4000 M Cisco 4500 M Cisco 4700 M Cisco 7000 series Cisco 7200 series and Cisco 7500 routers Figure 48 Autonomous FDDI SRB Virtual ring us To configure autonomous FDDI SRB use the following commands beginning in global configuration mode 83227 Step Command Purpose 1 interface fddi slot port Configure an FDDI interface 2 source bridge local ring bridge number Enable source route bridging target ring 3 source bridge route cache cbus Enable autonomous switching Configuring Source Route Bridging BC 113 Configure Source Route Bridging Configure Fast Switching SRB over FDDI Fast Switching SRB over FDDI enhances performance For example if you want to use access lists fast switching SRB over FDDI provides fast performance and access list filters capability To configure fast switching SRB over FDDI use the following commands beginning in global configuration mode Step Command Purpose 1 interface fddi slot port Configure an FDDI interface 2 source bridge local ring bridge number Enable source route bridging target ring 3 source bridge spanning Enable source bridge spanning 4 source bridge route cache Enable fast switching 5 multiring protocol keyword Enable the collection and use of RIF information Configure SR
21. switching of source route bridging frames Enable or Disable the Source Route Autonomous Switching Cache BC 140 Autonomous switching is a feature that enables the Cisco IOS software to transmit packets from the input ciscoBus card to the output ciscoBus card without any involvement on the part of the router processor Autonomous switching is available for local SRB between ciscoBus Token Ring CTR cards in the same router Autonomous switching provides higher switching rates than does fast switching between 4 16 Mb Token Ring cards Autonomous switching works for both two port bridges and multiport bridges that use ciscoBus Token Ring cards In a virtual ring that includes both ciscoBus Token Ring and 4 16 Mb Token Ring interfaces frames that flow from one CTR interface to another are autonomously switched and the remainder of the frames are fast switched The switching that occurs on the CTR interface takes advantage of the high speed ciscoBus controller processor To enable or disable source route autonomous switching use one of the following commands in interface configuration mode Command Purpose source bridge route cache cbus Enable autonomous switching no source bridge route cache cbus Disable autonomous switching Note Using either NetBIOS Byte Offset access filters or access expressions that combine access filters disables the autonomous switching of SRB frames Bridging and IBM Networking Configuratio
22. the French diplomat asks a question the translator does not know how to answer the translator must first translate the question to German wait for the German diplomat to answer and then translate the answer back to French Similarly if LNM queries a source route bridge in the proprietary protocol and the bridge knows the answer it responds directly using the same protocol If the bridge does not know the answer it must first translate the question to the IEEE 802 5 protocol query the station on the ring and then translate the response back to the proprietary protocol to send to LNM Figure 52 illustrates requests from the LNM originating in an IBM proprietary protocol and then translated into IEEE 802 5 MAC level frames Configuring Source Route Bridging BC 127 Configure LNM Support Figure 52 LAN Network Manager Monitoring and Translating LAN Network Manager Station A ge i Ring i Query to Station A lt _ gt Proprietary protocol i IEEE 802 5 on LLC2 Query about Station A p Token Ring 1114a Notice that the proprietary protocol LNM uses to communicate with the source route bridge is an LLC2 connection Although its protocol cannot be routed LNM can monitor or manage anything within the SRB network How a Router Works with LNM BC 128 As of Software Release 9 0 Cisco routers using 4 16 Mbps Token Ring interfaces configured for SRB support the proprietary protocol tha
23. the address of Host E on the Token Ring is not 0110 2222 3333 but rather 8008 4444 cccc resulting in the following configuration The following configuration is better This example shows that access lists for Token Ring and Ethernet should be kept completely separate from each other interface tokenring 0 source bridge input address list 702 interface ethernet 0 bridge group 1 input address list 701 l access list 701 permit 0110 2222 3333 li access list 702 permit 0110 1234 5678 NetBIOS Support with a Static NetBIOS Cache Entry Example BC 156 Figure 64 shows a NetBIOS client on a Token Ring connected through a cloud to a NetBIOS server on another Token Ring Figure 64 Specifying a Static Entry i Server DEF Client ABC 0110 222 333 Ring group 2 In Figure 64 a static entry is created in the router attached to ring 1 on the client side of the ring group The static entry is to the server DEF which is reached through the router attached to ring 3 If server DEF has the MAC address 0110 2222 3333 the configuration for the static entry on the client side is as follows rif 0110 2222 3333 0630 0021 0030 ring group 2 netbios name cache 0110 2222 3333 DEF ring group 2 Bridging and IBM Networking Configuration Guide LNM for a Simple Network Example LNM for a Simple Network Example Figure 65 shows a router with two Token Rings configured as a local source route bridge Figure 65 Router with Two Token Rings Con
24. the left as follows rif 1000 5A12 3456 0630 0081 0090 Adding a Static RIF Cache Entry for a Two Hop Path Example In Figure 61 assume that a datagram was sent from a router on ring 21 15 hexadecimal across Bridge 5 to ring 256 100 hexadecimal and then across Bridge 10 A hexadecimal to ring 1365 555 hexadecimal for delivery to a destination host on that ring Figure 61 Assigning a RIF to a Two Hop Path Om me Oe Bridge 5 Bridge 10 IBM PC 1000 5A01 0203 1101a The RIF in the router on the left describing this two hop path is 0830 0155 100a 5550 and is entered as follows rif 1000 5A01 0203 0830 0155 100a 5550 SR TLB for a Simple Network Example In the simple example illustrated in Figure 62 a four port router with two Ethernets and two Token Rings is used to connect transparent bridging on the Ethernets to SRB on the Token Rings Figure 62 Example of a Simple SR TLB Configuration 1274a Configuring Source Route Bridging BC 153 SRB Configuration Examples Assume that the following configuration for SRB and transparent bridging existed before you wanted to enable SR TLB interface tokenring 0 source bridge 1 1 2 l interface tokenring 1 source bridge 2 1 1 I interface ethernet 0 bridge group 1 l interface ethernet 0 bridge group 1 bridge 1 protocol dec To enable SR TLB one aspect of this configuration must change immediately a third ring must be configured Before SR
25. to point frame relay interface dlci 30 ietf source bridge 200 1 100 conserve ring source bridge spanning l interface Seriall 2 point to point frame relay interface dlci 31 ietf source bridge 300 1 100 conserve ring source bridge spanning interface TokenRing0O source bridge 500 1 100 Configuration on Router B source bridge ring group 200 l interface Serialo encapsulation frame relay l interface Serial0 30 point to point frame relay interface dlci 30 ietf source bridge 100 1 200 conserve ring source bridge spanning l interface TokenRing0 source bridge 600 1 200 Configuration on Router C source bridge ring group 300 interface Serial0 encapsulation frame relay l interface Serial0 31 point to point frame relay interface dlci 31 ietf source bridge 100 1 300 conserve ring source bridge spanning interface TokenRing0O source bridge 900 1 300 Adding a Static RIF Cache Entry Example In the example configuration in Figure 60 the path between rings 8 and 9 connected via Bridge 1 is described by the route descriptor 0081 0090 A full RIF including the route control field would be 0630 0081 0090 BC 152 Bridging and IBM Networking Configuration Guide Adding a Static RIF Cache Entry for a Two Hop Path Example Assigning a RIF to a Source Route Bridge Figure 60 r ss Token Token Cy Ring 8 Ring 9 oO Bridge 1 IBM PC S 1000 5A12 3456 5 The static RIF entry would be submitted to the router on
26. to set the express buffer bit to ensure priority service for frames required for ring station initiation When this function is enabled the router sets the express buffer bit in its initialize ring station response This allows Token Ring devices to insert into the ring during bursty conditions To enable LNM to use the RPS express buffer function use the following command in interface configuration mode Command Purpose Inm express buffer Enable the RPS express buffer function Monitor LNM Operation BC 132 Once LNM support is enabled you can monitor LNM operation To observe the configuration of the LNM bridge and its operating parameters use the following commands in the EXEC mode Step Command Purpose 1 show Inm bridge Display all configured bridges and their global parameters 2 show Inm config Display the logical configuration of all bridges configured in the router 3 show Inm interface type number Display LNM information for an interface or all interfaces of the router 4 show Inm ring ring number Display LNM information about a Token Ring or all Token Rings on the network 5 show Inm station address Display LNM information about a station or all stations on the network Bridging and IBM Networking Configuration Guide Secure the SRB Network Secure the SRB Network This section describes how to configure three features that are used primarily to provide network security
27. y a T T2 Token Token f Ring 1 Ring 2 g D Configuration for Router A source bridge ring group 100 interface tokenring 0 source bridge 3 4 100 source bridge spanning l interface tokenring 1 source bridge 1 4 100 source bridge spanning Configuring Source Route Bridging BC 149 SRB Configuration Examples Configuration for Router B source bridge ring group 200 l interface tokenring 0 source bridge 3 1 200 source bridge spanning l interface tokenring 2 source bridge 2 1 200 source bridge spanning SRB over FDDI Configuration Examples The following examples show the configuration for SRB over FDDI as illustrated in Figure 58 Router A dlsw local peer peer id 132 11 11 2 dlsw remote peer 0 tcp 132 11 11 3 interface Fddi0 no ip address multiring all source bridge 26 1 10 source bridge spanning Router B dlsw local peer peer id 132 11 11 2 dlsw remote peer 0 tcp 132 11 11 3 interface TokenRing0O no ip address ring speed 16 multiring all source bridge 25 1 10 source bridge spanning Figure 58 SRB over FDDI Configuration a FS a Cy Z aa Token a 3 O Router A Router B a on End station 2 SRB over FDDI Fast Switching Example The following example shows SRB over FDDI fast switching interface fddi 2 0 source bridge 1 10 2 source bridge spanning source bridge route cache multiring ip BC 150 Bridging and IBM Networking Configuration Guide SRB over Frame Relay Configuration E
28. you want to connect only a single machine Host E on an Ethernet to a single machine Host R on the Token Ring Figure 63 Example of a Bit Swapped Address Transparent Source route bridging domain bridged domain gt 5s Router Host E running SR TLB MAC Addr 0110 2222 3333 I fe a J 1110a MAC Addr 0110 1234 5678 You want to allow only these two machines to communicate across the router Therefore you might create the following configuration to restrict the access However this configuration will not work as explained in the paragraph following the sample configuration file Note For readability the commands that control bridging are not shown here just the commands that control the filtering interface tokenring 0 access expression output smac 701 l interface ethernet 0 bridge group 1 input address list 701 l access list 701 permit 0110 2222 3333 Configuring Source Route Bridging BC 155 SRB Configuration Examples The command for the Token Ring interface specifies that the access list 701 be applied on the source address of frames going out to the Token Ring and the command for the Ethernet interface specifies that this access list be applied on the source address frames entering the interface from Ethernet This would work if both interfaces used the same bit ordering but Token Rings and Ethernets use opposite swapped bit orderings in their addresses in relationship to each other Therefore
29. B over Frame Relay Cisco IOS software offers the ability to encapsulate source route bridging traffic using RFC 1490 Bridged 802 5 encapsulation This provides SRB over Frame Relay functionality that is interoperable with other vendors implementations of SRB over Frame Relay and with some vendors implementations of FRAS BAN Note In the initial release SRB over Frame Relay does not support the Cisco IOS software proxy explorer automatic spanning tree or LAN Network Manager functions To configure SRB over Frame Relay use the following commands in interface configuration mode Step Command Purpose 1 interface serial number Specify the serial port 2 encapsulation frame relay Enable Frame Relay encapsulation 3 interface serial slot port subinterface number Configure a Frame Relay point to point point to point subinterface 4 frame relay interface dlci dici ietf Configure a DLCI number for the point to point subinterface 5 source bridge source ring number bridge number Assign a ring number to the Frame target ring number conserve ring Relay permanent virtual circuit Enable the Forwarding and Blocking of Spanning Tree Explorers BC 114 When trying to determine the location of remote destinations on a source route bridge the source device will need to send explorer packets Explorer packets are used to collect routing information field RIF information The source device can send spanning tree explorer
30. BIOS Access Filters Example The show Inm config command displays the logical configuration of this bridge including all the pertinent information for configuring this router into LNM Wayfarer show lnm config Bridge s currently configured From ring 001 address 0000 0028 abcd Across bridge 001 To ring 008 address 4000 0028 abcd From ring 002 address 0000 3000 abc4 Across bridge 002 To ring 008 address 4000 3000 abc4 From ring 003 address 0000 3000 5735 Across bridge 003 To ring 008 address 4000 3000 5735 In this example six station definitions must be entered at the LNM Station one for each of the MAC addresses listed in this sample show Inm config display NetBIOS Access Filters Example The following command permits packets that include the station name ABCD to pass through the router but denies passage to packets that do not include the station name ABCD netbios access list host marketing permit ABCD The following command specifies a prefix where the pattern matches any name beginning with the characters DEFG Note that the string DEFG itself is included in this condition netbios access list host marketing deny DEFG The following command permits any station name with the letter W as the first character and the letter Y as the third character in the name The second and fourth letters in the name can be any character This example would allow stations named WXYZ and WAYB however stations named WY and WXY would
31. Cisco IOS software Note An access expression type filter cannot exist with a source bridge type filter on the same interface The two types of filters are mutually exclusive Alter Access Lists Used in Access Expressions Because access expressions are composed of access lists special care must be taken when deleting and adding access lists that are referenced in these access expressions If an access list that is referenced in an access expression is deleted the access expression merely ignores the deleted access list However if you want to redefine an access list you can create a new access list with the appropriate definition and use the same name as the old access list The newly defined access list replaces the old one of the same name For example if you want to redefine the NetBIOS access list named MIS that was used in the preceding example you would use the following sequence of configuration commands Replace the NetBIOS access list interface tokenring 0 access expression in smac 701 amp netbios host accept no netbios access list host accept permit CISCO Tune the SRB Network The following sections describe how to configure features that enhance network performance by reducing the number of packets that traverse the backbone network Enable or Disable the Source Route Fast Switching Cache Enable or Disable the Source Route Autonomous Switching Cache Enable or Disable the SSE Esta
32. Configure Translation between SRB and Transparent Bridging Environments Source route translational bridging SR TLB is a Cisco IOS software feature that allows you to combine SRB and transparent bridging networks without the need to convert all of your existing source route bridges to source route transparent SRT nodes As such it provides a cost effective connectivity path between Ethernets and Token Rings for example When a router is configured for SR TLB the router operates in fast switching mode by default causing packets to be processed in the interrupt handler when the packets first arrive rather than queuing them for scheduled processing You can also use the no source bridge transparent fastswitch command to disable fast switched SR TLB causing the router to handle packets by process switching For more information on disabling fast switched SR TLB refer to the Disable Fast Switched SR TLB section in this chapter Note When you are translationally bridging you will have to route routed protocols and translationally bridge all others such as local area transport LAT Overview of SR TLB You can bridge packets between an SRB domain and a transparent bridging domain Using this feature a software bridge is created between a specified virtual ring group and a transparent bridge group To the source route station this bridge looks like a standard source route bridge There is a ring number and a bridge number as
33. Note For any given interface an access expression cannot be used if an access list has been defined for a given direction For example if an input access list is defined for MAC addresses on an interface no access expression can be specified for the input side of that interface In Figure 53 two routers each connect a Token Ring to an FDDI backbone On both Token Rings SNA and NetBIOS bridging support is required On Token Ring A NetBIOS clients must communicate with any NetBIOS server off Token Ring B or any other unpictured router However the two 3174 cluster controllers off Token Ring A must only communicate with the one FEP off of Token Ring B located at MAC address 0110 2222 3333 Without access expressions this scenario cannot be achieved A filter on Router A that restricted access to only the FEP would also restrict access of the NetBIOS clients to the FEP What is needed is an access expression that would state If it is a NetBIOS frame pass through but if it is an SNA frame only allow access to address 0110 2222 3333 Figure 53 Access Expression Example NetBIOS clients NetBIOS servers Jg aya F D p ia cy Router A Router B address 3174 3174 0110 2222 3333 2 Note Using access expressions that combine access filters disables the autonomous or fast switching of source route bridging frames Configuring Source Route Bridging BC 137 Secure the SRB Network Configure Access Exp
34. OS software can forward broadcast requests sent by clients to find servers and by servers in reply to their clients directly to their needed destinations rather than forwarding them for broadcast across the entire bridged network The software will time out the entries in the NetBIOS name cache after a specific interval of their initial storage The timeout value is a user configurable value You can configure the timeout value for a particular Token Ring if the NetBIOS name cache is enabled on the interface connecting to that Token Ring In addition you can configure static name cache entries that never time out for frequently accessed servers whose locations or paths typically do not change Static RIF entries are also specified for such hosts Generally NetBIOS name caching is most useful when a large amount of NetBIOS broadcast traffic creates bottlenecks on WAN media connecting distant locations and the WAN media is overwhelmed with this traffic However when two high speed LAN segments are directly interconnected the packet savings of NetBIOS name caching is probably not worth the processor overhead associated with it Note NetBIOS name caching is not recommended to be turned on in backbone routers particularly if you have it enabled in all the routers connected to the backbone NetBIOS caching should be distributed among multiple routers NetBIOS name caching can be used only between Cisco routers that are running Software Release 9 1
35. Token Ring 1 Figure 67 Router Filtering Bridged Token Ring Packets to IBM Machines 3174 3174 eS Token y T1 Ring 1 Z T2 3174 Token Z amp Ring 2 Z NI N This example assumes that all hosts on Token Ring 1 have Token Ring addresses with the vendor code 1000 5A00 0000 The first line of the access list denies access to all IBM workstations while the second line permits everything else The access list is assigned to the input side of Token Ring 1 deny access to all IBM workstations access list 700 deny 1000 5A00 0000 8000 00FF FFFF permit all other traffic access list 700 permit 0000 0000 0000 FFFF FFFF FFFF 1 interface token ring 1 apply access list 700 to the input side of Token Ring 1 source bridge input address list 700 BC 160 Bridging and IBM Networking Configuration Guide Administrative Access Filters Filtering SNAP Frames on Output Example Administrative Access Filters Filtering SNAP Frames on Output Example Figure 68 shows a router connecting four Token Rings Figure 68 Router Filtering SNAP Frames on Output The following example allows only AppleTalk Phase 2 packets to be source route bridged between Token Rings 0 and 1 and allows Novell packets only to be source route bridged between Token Rings 2 and 3 source bridge ring group 5 I interface tokenring 0 ip address 131 108 1 1 255 255 255 0 source bridge 1000 1 5 source bridge spanning source bridge input type list 202 I int
36. access list you specify is the one you created that includes the protocol type codes Configuring Source Route Bridging BC 135 Secure the SRB Network To enable filtering on input or output use one of the following commands in interface configuration mode Command Purpose source bridge input Isap list access list number Enable filtering of IEEE 802 encapsulated packets on input by type code source bridge output lsap list access list number Enable filtering of IEEE 802 encapsulated packets on output by type code You can filter SNAP encapsulated packets on either input or output The access list you specify is the one you created that includes the protocol type codes To enable filtering on input or output use one of the following commands in interface configuration mode Command Purpose source bridge input type list access list number Filter SNAP encapsulated packets on input by type code source bridge output type list access list number Filter SNAP encapsulated frames on output by type code Filter Frames by Vendor Code To configure administrative filters by vendor code or address define access lists that look for Token Ring addresses or for particular vendor codes for administrative filtering To do so use the following command in global configuration mode Purpose Command access list access list number permit deny address Configure vendor code access lists mask Filter Sourc
37. ace configuration mode Command Purpose Inm alternate number Enable a LRM other than that connected through link 0 to change router parameters Apply a Password to an LNM Reporting Link Each reporting link has its own password that is used not only to prevent unauthorized access from an LRM to a bridge but to control access to the different reporting links This is important because it is possible to change parameters through some reporting links To apply a password to an LNM reporting link use the following command in interface configuration mode Command Purpose Inm password number string Apply a password to an LNM reporting link Enable LNM Servers As in an IBM bridge the router provides several functions that gather information from a local Token Ring All of these functions are enabled by default but also can be disabled The LNM servers are explained in the section How a Router Works with LNM earlier in this chapter To enable LNM servers use one or more of the following commands in interface configuration mode Command Purpose Inm crs Enable the LNM Configuration Report Server CRS Inm rem Enable the LNM Ring Error Monitor REM Inm rps Enable the LNM Ring Parameter Server RPS Change Reporting Thresholds The Cisco IOS software sends a message to all attached LNMs whenever it begins to drop frames The threshold at which this report is generated is based on a perce
38. ansparent bridging domain are not passed between the SRB domain and the transparent bridging domain Therefore you must not set up multiple paths between the SRB and transparent bridging domains The following notes and caveats apply to all uses of SR TLB Multiple paths cannot exist between the source route bridged domain and the transparent bridged domain Such paths can lead to data loops in the network because the spanning tree packets used to avoid these loops in transparent bridging networks do not traverse the SRB network Some devices notably PS 2s under certain configurations running OS 2 Extended Edition Version 1 3 do not correctly implement the largest frame processing on RIFs received from remote source route bridged hosts The maximum Ethernet frame size is smaller than that allowed for Token Ring As such bridges allowing for communication between Ethernet and Token Ring will tell the Token Ring hosts through the RIF on frames destined to the Token Ring that hosts on the Ethernet cannot receive frames larger than a specified maximum typically 1472 bytes Some machines ignore this run time limit specification and send frames larger than the Ethernet can accept The router and any other Token Ring Ethernet bridge has no choice but to drop these frames To allow such hosts to successfully communicate across or to an Ethernet you must configure their maximum frame sizes manually For the PS 2 this can be done through Com
39. blish the Connection Timeout Interval Optimize Explorer Processing Configure Proxy Explorers Note In some situations you might discover that default settings for LLC2 configurations are not acceptable In such a case you can configure LLC2 for optimal use The chapter Configuring LLC2 and SDLC Parameters in this publication describes how you can use them to optimize your network performance Configuring Source Route Bridging BC 139 Tune the SRB Network Enable or Disable the Source Route Fast Switching Cache Rather than processing packets at the process level the fast switching feature enables the Cisco IOS software to process packets at the interrupt level Each packet is transferred from the input interface to the output interface without copying the entire packet to main system memory Fast switching allows for faster implementations of local SRB between 4 16 MB Token Ring cards in the same router or between two routers using the 4 16 Mb Token Ring cards and direct encapsulation By default fast switching software is enabled when SRB is enabled To enable or disable source route fast switching use one of the following commands in interface configuration mode Command Purpose source bridge route cache Enable fast switching no source bridge route cache Disable fast switching Note Using either NetBIOS Byte Offset access filters or access expressions that combine access filters disables the fast
40. bridge spanning multiring all E interface tokenring 1 ip address 131 108 130 2 255 255 255 0 xns network 130 novell network 130 source bridge 130 1 129 source bridge spanning multiring all I interface ethernet 0 ip address 131 108 2 68 255 255 255 0 xns network 2 novell network 2 Multiport SRB Example Figure 56 shows an example configuration of a four port Token Ring source route bridge Rings 1000 1001 1002 and 1003 are all source route bridged to each other across ring group 7 Figure 56 Four Port Source Route Bridge Ring 1001 T1 Aa Ring ce Fa TO Ring 1002 1000 T3 Ring Group 7 Ring 1003 1103a BC 148 Bridging and IBM Networking Configuration Guide SRB with Multiple Virtual Ring Groups Example The following is a sample configuration file source bridge ring group 7 l interface tokenring 0 source bridge 1000 1 7 source bridge spanning l interface tokenring 1 source bridge 1001 1 7 source bridge spanning interface tokenring 2 source bridge 1002 1 7 source bridge spanning l interface tokenring 3 source bridge 1003 1 7 source bridge spanning SRB with Multiple Virtual Ring Groups Example Two virtual ring groups can only be connected through an actual Token Ring Figure 57 shows Virtual Rings 100 and 200 connected through Token Ring 3 Figure 57 Two Virtual Rings Connected by an Actual Token Ring Virtual ring 100 Virtual ring 200 Router A a fone SO So
41. e Addresses To configure filtering on IEEE 802 source addresses assign an access list to a particular input interface for filtering the Token Ring or IEEE 802 source addresses To do so use the following command in interface configuration mode Command Purpose source bridge input address list access list number Enable filtering on IEEE 802 source addresses Filter Destination Addresses To configure filtering on IEEE 802 destination addresses assign an access list to a particular output interface To do so use the following command in interface configuration mode Command Purpose source bridge output address list access list number Enable filtering on IEEE 802 destination addresses BC 136 Bridging and IBM Networking Configuration Guide Configure Access Expressions that Combine Administrative Filters Configure Access Expressions that Combine Administrative Filters You can use access expressions to combine access filters to establish complex conditions under which bridged frames can enter or leave an interface Using access expressions you can achieve levels of control on the forwarding of frames that otherwise would be impossible when using only simple access filters Access expressions are constructed from individual access lists that define administrative filters for the following fields in packets LSAP and SNAP type codes MAC addresses NetBIOS station names NetBIOS arbitrary byte values
42. e destination name field for NetBIOS commands 08 OA and OE DATAGRAM NAME_QUERY and NAME_RECOGNIZED If an access list does not contain a particular station name the default action is to deny the access to that station To minimize any performance degradation NetBIOS access filters do not examine all packets Rather they examine certain packets that are used to establish and maintain NetBIOS client server connections thereby effectively stopping new access and load across the router However applying a new access filter does not terminate existing sessions immediately All new sessions will be filtered but existing sessions could continue for some time There are two ways you can configure NetBIOS access filters Configure NetBIOS Access Filters Using Station Names Configure NetBIOS Access Filters Using a Byte Offset Configure NetBIOS Access Filters Using Station Names To configure access filters using station names you must do the following Step 1 Assign the station access list name Step 2 Specify the direction of the message to be filtered on the interface Configuring Source Route Bridging BC 133 Secure the SRB Network The NetBIOS station access list contains the station name to match along with a permit or deny condition You must assign the name of the access list to a station or set of stations on the network To assign a station access list name use the following command in global configuration mode
43. e the SRB and Routing Certain Protocols Example section later in this chapter Configure a Static RIF Entry If a Token Ring host does not support the use of IEEE 802 2 TEST or XID datagrams as explorer packets you might need to add static information to the RIF cache of the router To configure a static RIF entry use the following command in global configuration mode Command Purpose rif mac address rif string interface name ring group Enter static source route information ring into the RIF cache Configure the RIF Timeout Interval RIF information that can be used to bridge routed protocols is maintained in a cache whose entries are aged Note The rif validate enable commands have no effect on remote entries learned over RSRB To configure the number of minutes an inactive RIF entry is kept in the cache use the following commands in global configuration mode Step Command Purpose 1 rif timeout minutes Specify the number of minutes an inactive RIF entry is kept 2 rif validate enable Enable RIF validation for entries learned on an interface Token Ring or FDDI 3 rif validate enable age Enable RIF validation on an SRB that is malfunctioning 4 rif validate enable route cache Enable synchronization of the RIF cache with the protocol route cache BC 118 Bridging and IBM Networking Configuration Guide Configure Translation between SRB and Transparent Bridging Environments
44. erface tokenring 1 ip address 131 108 11 1 255 255 255 0 source bridge 1001 1 5 source bridge spanning source bridge input type list 202 I interface tokenring 2 ip address 131 108 101 1 255 255 255 0 source bridge 1002 1 5 source bridge spanning source bridge input lsap list 203 I interface tokenring 3 ip address 131 108 111 1 255 255 255 0 source bridge 1003 1 5 source bridge spanning source bridge input lsap list 203 SNAP type code filtering permit ATp2 data 0x809B permit ATp2 AARP 0x80F3 access list 202 permit 0x809B 0x0000 access list 202 permit 0x80F3 0x0000 access list 202 deny 0x0000 OxFFFF I LSAP filtering permit IPX 0xEOEO Configuring Source Route Bridging BC 161 SRB Configuration Examples access list 203 permit OxEOEO 0x0101 access list 203 deny 0x0000 OxFFFF Note that it is not necessary to check for an LSAP of OxAAAA when filtering SNAP encapsulated AppleTalk packets because for source route bridging the use of type filters implies SNAP encapsulation Creating Access Filters Example BC 162 In math you have the following 3 x 4 2 14 but 3 x 4 2 18 Similarly the following access expressions would return TRUE if lsap 201 and dmac 701 returned TRUE or if smac 702 returned TRUE lsap 201 amp dmac 701 smac 702 However the following access expression would return TRUE only if lsap 201 returned TRUE and either of dmac 701 or smac 702 returned
45. figured as a Local Source Route Bridge Physical configuration Token ma 1 Token Ring 1 TO i y Ring 3 Logical configuration S1115a The associated configuration file follows interface tokenring 0 source bridge 1 2 3 l interface tokenring 1 source bridge 3 2 1 The show Inm config command displays the logical configuration of this bridge including the LNM configuration information that needs to be entered at the LNM Station A sample show Inm config display follows Wayfarer show lnm config Bridge s currently configured From ring 001 address 0000 3000 abc4 Across bridge 002 To ring 003 address 0000 3000 5735 In this example the MAC addresses 0000 3000 abc4 and 000 3000 5735 must be configured as Adapter Addresses at the LNM Station Configuring Source Route Bridging BC 157 SRB Configuration Examples LNM for a More Complex Network Example Figure 66 shows a router with three Token Rings configured as a multiport bridge thus employing the concept of the virtual ring Figure 66 Router with Three Token Rings Configured as a Multiport Bridge Token Ring 2 Physical configuration Token Ring 1 Logical configuration The associated configuration file follows source bridge ring group 8 l interface tokenring 0 source bridge 1 1 8 interface tokenring 1 source bridge 2 2 8 l interface tokenring 2 source bridge 3 3 8 BC 158 Bridging and IBM Networking Configuration Guide Net
46. ging of Routed Protocols Source route bridges use Media Access Control MAC information specifically the information contained in the RIF to bridge packets A RIF contains a series of ring and bridge numbers that represent the possible paths the source node might use to send packets to the destination Each ring number in the RIF represents a single Token Ring in the source route bridged network and is designated by a unique 12 bit ring number Each bridge number represents a bridge that is between two Token Rings in the SRB network and is designated by a unique 4 bit bridge number The information in a RIF is derived from explorer packets traversing the source route bridged network Without the RIF information a packet could not be bridged across a source route bridged network Unlike source route bridges Level 3 routers use protocol specific information for example Novell Internetwork Packet Exchange IPX or Xerox Network Systems XNS headers rather than MAC information to route datagrams As a result the Cisco IOS software default for routed protocols is to not collect RIF information and to not be able to bridge routed protocols However if you want the software to bridge routed protocols across a source route bridged network the software must be able to collect and use RIF information to bridge packets across a source route bridged network You can configure the software to append RIF information to routed protocols so that routed protocol
47. ing interfaces that connect to the two Token Rings To enable source route bridging use the following command in interface configuration mode for each of the Token Ring interfaces Command Purpose source bridge local ring bridge number target ring Enable local source route bridging on a Token Ring interface Note Ring numbers need to be unique across interfaces and networks so that when you enable source route bridging over an interface the local and target rings are defined Each node on the network will know if it is the target of explorer packets sent on the network Bridging and IBM Networking Configuration Guide Configure a Multiport Bridge Using a Virtual Ring A dual port bridge is a limitation imposed by IBM Token Ring chips the chips can process only two ring numbers If you have a router with two or more Token Ring interfaces you can work around the two ring number limitation You can configure your router as multiple dual port bridges or as a multiport bridge using a virtual ring You can define several separate dual port bridges in the same router However the routers on the LANs cannot have any to any connectivity that is they cannot connect to every other router on the bridged LANs Only the routers connected to the dual port bridge can communicate with one another Figure 46 shows two separate dual port bridges TO T2 and T1 T3 configured on the same router Figure 46 Multiple Dual Port Bridges Token
48. is to only the nodes on the spanning tree not to all nodes in the network You must manually configure the spanning tree topology over which the spanning tree explorers are sent You do this by configuring which interfaces on the routers will forward spanning tree explorers and which interfaces will block them To enable forwarding of spanning tree explorers on an outgoing interface use the following command in interface configuration mode Command Purpose source bridge spanning Enable the forwarding of spanning tree explorer packets on an interface Note While enabling the forwarding of spanning tree explorer packets is not an absolute requirement it is strongly recommended in complex topologies Configuring an interface to block or forward spanning tree explorers has no effect on how that interface handles all routes explorer packets All routes explorers can always traverse the network To block forwarding of spanning tree explorers on an outgoing interface use the following command in interface configuration mode Command Purpose no source bridge spanning Block spanning tree explorer packets on an interface Enable the Automatic Spanning Tree Function The automatic spanning tree function supports automatic resolution of spanning trees in SRB networks which provides a single path for spanning explorer frames to traverse from a given node in the network to another Spanning explorer frames have a single route
49. m byte rate of explorers per ring You must also disable explorer fast switching which is by default enabled To disable explorer fast switching use the following command in global configuration mode Command Purpose no source bridge explorer fastswitch Disable explorer fast switching To enable explorer fast switching after it has been disabled use the following command in global configuration mode Command Purpose source bridge explorer fastswitch Enable explorer fast switching Bridging and IBM Networking Configuration Guide Configure Proxy Explorers Configure Proxy Explorers You can use the proxy explorers feature to limit the amount of explorer traffic propagating through the source bridge network To configure proxy explorers use the following command in interface configuration mode Command Purpose source bridge proxy explorer Enable the interface to respond to any explorer packets that meet certain conditions necessary for a proxy response to occur The Cisco IOS software does not propagate proxy responses for a station Instead the software obtains the RIF path from the RIF cache changes the explorer to a specific frame and forwards this frame to the destination If a response is not received before the validation timer expires the RIF entry is marked as invalid The invalid RIF entry is flushed from the cache table when another explorer for this station is received and an ex
50. mand and response frames to pass equally To apply the access expression to the appropriate interface enter the following command in interface configuration mode Command Purpose access expression in out expression Define a per interface access expression Optimize Access Expressions BC 138 It is possible to combine access expressions Suppose you wanted to transmit SNA traffic through to a single address but allow other traffic through the router without restriction The phrase could be written as follows Allow access if the frame is not an SNA frame or if it is going to host 0110 2222 3333 More tersely this would be Not SNA or destined to 0110 2222 3333 Bridging and IBM Networking Configuration Guide Tune the SRB Network The access lists defined in the previous section create the following configuration interface tokenring 0 access expression in lsap 202 dmac 701 l access list 202 permit 0x0404 0x0001 Permits SNA frames command or response access list 202 permit 0x0004 0x0001 Permits SNA Explorers with NULL DSAP Access list 701 will permit the FEP MAC address Lof 0110 22223333 access list 701 permit 0110 2222 3333 This is a better and simpler access list than the one originally introduced and will probably result in better run time execution as a result Therefore it is best to simplify your access expressions as much as possible before configuring them into the
51. municate with LNM and to provide the functionality of the IBM Bridge Program our device appears as part of the IBM network You therefore gain from the interconnectivity of our products without having to learn a new management product or interface Bridging and IBM Networking Configuration Guide Configure LNM Software on the Management Stations to Communicate with the Router When SRB is enabled on the router configuring the Cisco IOS software to perform the functions of an IBM Bridge for communication with LNM occurs automatically Therefore if SRB has been enabled you do not need to perform any tasks to enable LNM support However the LNM software residing on a management station on a Token Ring on the network should be configured to properly communicate with the router There are several options for modifying LNM parameters in the Cisco IOS software but none are required for basic functionality For example because users can now modify the operation of the Cisco IOS software through SNMP as well as through LNM there is an option to exclude a user from modifying the Cisco IOS software configuration through LNM You also can specify which of the three LNM services CRS REM RPS the source route bridge will perform To configure LNM support perform the tasks in the following sections Configure LNM Software on the Management Stations to Communicate with the Router Disable LNM Functionality Disable Automatic Report Path Trace
52. munications Manager Any access filters applied on any frames apply to the frames as they appear on the media to which the interface with the access filter applies This is important because in the most common use of SR TLB Ethernet and Token Ring connectivity the bit ordering of the MAC addresses in the frame is swapped Refer to the SR TLB examples in the SRB Configuration Examples section of this chapter Caution Bridging between dissimilar media presents several problems that can prevent communication A from occurring These problems include bit order translation or usage of MAC addresses as data maximum transmission unit MTU differences frame status differences and multicast address usage Some or all of these problems might be present in a multimedia bridged LAN and prevent communication from taking place Because of differences in the way end nodes implement Token Ring these problems are most prevalent when bridging between Token Rings and Ethernets or between Token Ring and FDDI LANs Bridging and IBM Networking Configuration Guide Enable Bridging between Transparent Bridging and SRB We currently know that problems occur with the following protocols when bridged between Token Ring and other media Novell IPX DECnet Phase IV AppleTalk VINES XNS and IP Further problems can occur with the Novell IPX and XNS protocols when bridged between FDDI and other media We recommend that these protocols be routed whenever po
53. n Guide Enable or Disable the SSE Enable or Disable the SSE The Silicon Switch Engine SSE acts as a programmable cache to speed the switching of packets To enable or disable the SSE use one of the following commands in interface configuration mode Command Purpose source bridge route cache sse Enable the SSE function no source bridge route cache sse Disable the SSE function Establish the Connection Timeout Interval It may be necessary to adjust timeout intervals in a complex topology such as a large multihop WAN with virtual rings or satellite links The timeout interval is used when a connection to a remote peer is attempted If the timeout interval expires before a response is received the connection attempt is aborted To set the connection timeout interval use the following command in global configuration mode Command Purpose source bridge connection timeout seconds Set the connection timeout interval Optimize Explorer Processing Efficient explorer processing is vital to the operation of SRB The default configuration is satisfactory for most situations However there might be circumstances that create unexpected broadcast storms You can optimize the handling of explorer frames thus reducing processor overhead and increasing explorer packet throughput Optimizing explorer processing enables the router to perform substantially better during explorer broadcast storms In networks with redunda
54. ne of its interfaces show Inm config Display the logical multiport bridge configuration of the Cisco IOS software show Inm interface type number Display all LNM relevant information about a specific interface show Inm ring ring number Display all LNM relevant information about a specific ring number show Inm station address Display all LNM relevant information about a specific station or about all known stations on the ring show local ack Show the current state of any current local acknowledgment for both LLC2 and SDLLC connections show netbios cache Display the contents of the NetBIOS cache show rif Display the contents of the RIF cache show source bridge interface Bridging and IBM Networking Configuration Guide Display the current source bridge configuration and miscellaneous statistics SRB Configuration Examples Command Purpose show span Display the spanning tree topology for the router show sse summary Display a summary of Silicon Switch Processor SSP statistics To maintain the SRB network use any of the following commands in privileged EXEC mode Command Purpose clear netbios cache Clear the entries of all dynamically learned NetBIOS names clear rif cache Clear the entire RIF cache clear source bridge Clear the SRB statistical counters clear sse Reinitialize the SSP on the Cisco 7000 series
55. ng Access Filters Example Access Filters Example Fast Switching Example Autonomous Switching Example Basic SRB with Spanning Tree Explorers Example BC 146 Token TO E Figure 55 illustrates a simple two port bridge configuration Token Rings 129 and 130 are connected through the router Figure 55 Dual Port Source Route Bridge Configuration Ring 129 S1102a The example that follows routes IP but source route bridges all other protocols using spanning tree explorers interface tokenring 0 ip address 131 108 129 2 255 255 255 0 source bridge 129 1 130 source bridge spanning multiring all 1 interface tokenring 1 ip address 131 108 130 2 255 255 255 0 source bridge 130 1 129 source bridge spanning use RIFs as necessary with IP routing software multiring all Bridging and IBM Networking Configuration Guide SRB with Automatic Spanning Tree Function Configuration Example SRB with Automatic Spanning Tree Function Configuration Example The following example of a Cisco series 7000 router configuration illustrates how to enable the automatic spanning tree function on an SRB network source bridge ring group 100 interface tokenring 0 0 no ip address ring speed 16 multiring all source bridge active 1 10 100 source bridge spanning 1 I interface tokenring 0 1 no ip address ring speed 16 multiring all source bridge active 2 10 100 source bridge spanning 1 I bridge 1 protocol ibm Optimized E
56. ng interface on the router must be configured to belong to the same ring group For information about configuring a multiport bridge using a virtual ring see the Configure a Multiport Bridge Using a Virtual Ring section later in this chapter To configure a source route bridge to have more than two network interfaces you must perform the following tasks Step 1 Define a ring group Step 2 Enable source route bridging and assign a ring group to a Token Ring interface Once you have completed these tasks the router acts as a multiport bridge not as a dual port bridge Note Ring numbers need to be unique across interfaces and networks Define a Ring Group in SRB Context BC 112 Because all IBM Token Ring chips can process only two ring numbers we have implemented the concept of a ring group or virtual ring A ring group is a collection of Token Ring interfaces in one or more routers that share the same ring number This ring number is used just like a physical ring number showing up in any route descriptors contained in packets being bridged Within the context of a multiport bridge that uses SRB rather than RSRB the ring group resides in the same router See the Configuring Remote Source Route Bridging chapter to compare ring groups in the SRB and RSRB context A ring group must be assigned a ring number that is unique throughout the network It is possible to assign different Token Ring interfaces on the same router to
57. nt topologies two or more routers connected to the same set of Token Rings and doing source route bridging a station on one Token Ring trying to get to a station on another Token Ring may choose a less than optimal route through unnecessary routers causing explorer storms due to excessive forwarding of explorer frames For example in the redundant topology example shown in Figure 54 if Station X on Token Ring 1 attempts to get to Station Z on Token Ring 4 by going through Router A Token Ring 2 and Router B a less than optimal route excessive forwarding of explorer frames may cause explorer storms Configuring Source Route Bridging BC 141 Tune the SRB Network BC 142 Figure 54 Controlling Explorer Storms in Redundant Network Topologies Token Ring 1 Token Ring 2 7 um cre i a J Router A i a Hf Router B Token Ring 3 Token Ring 4 BODDU 5002 The source bridge explorer dup A RE filter command can be used to reduce explorer traffic by filtering explorer frames To optimize explorer processing use one or more of the following commands in global configuration mode Command Purpose source bridge explorerq depth depth Set the maximum explorer queue depth source bridge explorer dup ARE filter Prevent explorer storms in redundant network topologies by filtering explorers that have already been forwarded once source bridge explorer maxrate maxrate Set the maximu
58. ntage of frames dropped compared with those forwarded This threshold is configurable and defaults to a value of 0 10 percent You can configure the threshold by entering a single number expressing the percentage loss rate in hundredths of a percent The valid range is 0 to 9999 To change reporting thresholds use the following command in interface configuration mode Command Purpose Inm loss threshold number Change the threshold at which the Cisco IOS software reports the frames lost percentage to LNM Configuring Source Route Bridging BC 131 Configure LNM Support Change an LNM Reporting Interval All stations on a Token Ring notify the Ring Error Monitor REM when they detect errors on the ring In order to prevent excessive messages error reports are not sent immediately but are accumulated for a short interval and then reported A station learns the duration of this interval from a router configured as a source route bridge when it first enters the ring This value is expressed in tens of milliseconds between error messages The default is 200 or 2 seconds The valid range is 0 to 65535 To change an LNM reporting interval use the following command in interface configuration mode Command Purpose Inm softerr milliseconds Set the time interval during which stations report ring errors to the Ring Error Monitor REM Enable the RPS Express Buffer Function The RPS express buffer function allows the router
59. nterfaces 0 or 1 will be autonomously switched to the other interface global command to apply interface configuration commands to the ring group source bridge ring group 2 1 commands that follow apply to interface token 0 interface tokenring 0 enable srb between local ring 1 bridge 1 and target ring 2 source bridge 1 1 2 enable autonomous switching for interface token 0 source bridge route cache cbus I interface tokenring 1 enable srb between local ring 2 bridge 1 and target ring 1 source bridge 2 1 1 source bridge route cache cbus BC 164 Bridging and IBM Networking Configuration Guide
60. oes not exist look for the source bridge proxy netbios only entry for the appropriate interface If neither entry exists proxy explorers has not yet been enabled for the appropriate interface To enable proxy explorers for response to all explorer packets refer to the section Configure Proxy Explorers later in this chapter Otherwise enable proxy explorers only for the NetBIOS name caching function by using the following command in global configuration mode Command Purpose source bridge proxy netbios only Enable use of proxy explorers only for the NetBIOS name caching function and not for their general local response to explorers Specify Timeout and Enable NetBIOS Name Caching BC 124 After you have ensured that the proxy explorers feature has been enabled for the appropriate interface you can specify a cache timeout and enable NetBIOS name caching To do this use the following commands Step Command Purpose 1 netbios name cache timeout minutes Specify the timeout for entries in the NetBIOS name cache 2 netbios enable name cache Enable NetBIOS name caching for the appropriate interfaces Bridging and IBM Networking Configuration Guide Configure the NetBIOS Cache Name Length Configure the NetBIOS Cache Name Length To specify how many characters of the NetBIOS type name that the name cache will validate enter the following command in global configuration mode Command Purpose
61. plorer is forwarded to discover a path to this station Establish SRB Interoperability with Specific Token Ring Implementations This section describes how you can establish interoperability between routers and specific Token Ring implementations It includes the following sections Establish SRB Interoperability with TI MAC Firmware Report Spurious Frame Copied Errors Establish SRB Interoperability with TI MAC Firmware You can use a workaround to establish interoperability with Texas Instruments MAC firmware There is a known defect in earlier versions of the Texas Instruments Token Ring MAC firmware This implementation is used by Proteon Apollo and IBM RTs A host using a MAC address whose first two bytes are zeros such as a Cisco router will not properly communicate with hosts using that version of Texas Instruments firmware There are two solutions The first involves installing a static RIF entry for every faulty node with which the router communicates If there are many such nodes on the ring this may not be practical You also can set the MAC address of our Token Ring to a value that works around the problem Resetting the MAC address forces the use of a different MAC address on the specified interface thereby avoiding the TI MAC firmware problem However you must ensure that no other host on the network is using that MAC address To reset the MAC address use the following command in interface configuration mode
62. ransit oui 90 compatible standard cisco Move data between IBM 8209 Ethernet Token Ring bridges and routers running translational bridging software Configuring Source Route Bridging BC 121 Configure Translation between SRB and Transparent Bridging Environments Enable Token Ring LLC2 to Ethernet Conversion The Cisco IOS software supports the following types of Token Ring to Ethernet frame conversions using Logical Link Control type 2 LLC2 Protocol Token Ring LLC2 to Ethernet Type II 0x80d5 processing Token Ring LLC2 to Ethernet 802 3 LLC2 standard For most non IBM hosts Token Ring LLC2 frames can be translated in a straightforward manner into Ethernet 802 3 LLC2 frames This is the default conversion in the Cisco IOS software However many Ethernet attached IBM devices use nonstandard encapsulation of LLC2 on Ethernet Such IBM devices including PS 2s running OS 2 Extended Edition and RT PCs do not place their LLC2 data inside an 802 3 format frame but rather place it into an Ethernet Type 2 frame whose type is specified as 0x80d5 This nonstandard format is called 0x80d5 named after the type of frame This format is also sometimes called RT PC Ethernet format because these frames were first widely seen on the RT PC Hosts using this nonstandard 0x80d5 format cannot read the standard Token Ring LLC2 to Ethernet 802 2 LLC frames To enable Token Ring LLC2 to Ethernet LLC2 conversion you can perform one or both
63. ranslation on a per DSAP basis BC 122 Bridging and IBM Networking Configuration Guide Configure NetBIOS Support Configure NetBIOS Support NetBIOS is a nonroutable protocol that was originally designed to transmit messages between stations typically IBM PCs on a Token Ring network NetBIOS allows messages to be exchanged between the stations using a name rather than a station address Each station knows its name and is responsible for knowing the names of other stations on the network Note In addition to this type of NetBIOS which runs over LLC2 we have implemented another type of NetBIOS that runs over IPX For information on the IPX type of NetBIOS refer to the chapter Configuring Novell IPX in the Network Protocols Configuration Guide Part 2 NetBIOS name caching allows the Cisco IOS software to maintain a cache of NetBIOS names which avoids the high overhead of transmitting many of the broadcasts used between client and server NetBIOS PCs IBM PCs or PS 2s in an SRB environment When NetBIOS name caching is enabled the software performs the following actions Notices when any hosts send a series of duplicated query frames and reduces them to one frame per period The time period is configurable Keeps a cache of mappings between NetBIOS server and client names and their MAC addresses By watching NAME_QUERY and NAME_RECOGNIZED request and response traffic between clients and servers the Cisco I
64. ressions To configure an access expression perform the following tasks Design the access expression Configure the access lists used by the expression Configure the access expression into the router When designing an access expression you must create some phrase that indicates in its entirety all the frames that will pass the access expression This access expression is designed to apply on frames coming from the Token Ring interface on Router A in Figure 53 Pass the frame if it is a NetBIOS frame or if it is an SNA frame destined to address 0110 2222 3333 In Boolean form this phrase can be written as follows Pass if NetBIOS or SNA and destined to 0110 2222 3333 The preceding statement requires three access lists to be configured An access list that passes a frame if it is a NetBIOS frame SAP OxFOFO An access list that passes a frame if it is an SNA frame SAP 0x0404 An access list that passes a MAC address of 0110 2222 3333 The following configuration allows for all these conditions Access list 201 passes NetBIOS frames command or response access list 201 permit OxFOFO 0x0001 l access list 202 permit 0x0404 0x0001 Permits SNA frames command or response access list 202 permit 0x0004 0x0001 Permits SNA Explorers with NULL DSAP Access list 701 will permit the FEP MAC address i of 0110 2222 3333 access list 701 permit 0110 2222 3333 The 0x0001 mask allows com
65. rotocol type IEEE 802 or Subnetwork Access Protocol SNAP Token Ring vendor code Source address Destination address Whereas filtering by Token Ring address or vendor code causes no significant performance penalty filtering by protocol type significantly affects performance A list of SNAP Ethernet type codes is provided in the Ethernet Type Codes appendix in the Bridging and IBM Networking Command Reference Filter Frames by Protocol Type You can configure administrative filters by protocol type by specifying protocol type codes in an access list You then apply that access list to either IEEE 802 2 encapsulated packets or to SNAP encapsulated packets on the appropriate interface The order in which you specify these elements affects the order in which the access conditions are checked Each condition is tested in succession A matching condition is then used to execute a permit or deny decision If no conditions match a deny decision is reached Note Ifa single condition is to be denied there must be an access list command that permits everything as well or all access is denied To filter frames by protocol type use the following command in global configuration mode Command Purpose access list access list number permit deny type code Create an access list for filtering wild mask address mask frames by protocol type You can filter IEEE 802 encapsulated packets on either input or output The
66. s can be bridged Figure 49 shows a network topology in which you would want to use this feature Figure 49 Topology for Bridging Routed Protocols across a Source Route Bridged Network Cisco routed network Cisco routed network Source route bridged Token Ring network 2328 To configure the Cisco IOS software to bridge routed protocols you must perform the task in the first section and optionally one or both of the tasks in the other sections as follows Enable Use of the RIF Configure a Static RIF Entry Configure the RIF Timeout Interval Enable Use of the RIF You can configure the Cisco IOS software so that it will append RIF information to the routed protocols This allows routed protocols to be bridged across a source route bridged network The routed protocols that you can bridge are as follows Apollo Domain AppleTalk ISO Connectionless Network Service CLNS DECnet JP IPX Configuring Source Route Bridging BC 117 Configure Bridging of Routed Protocols VINES XNS Enable use of the RIF only on Token Ring interfaces on the router To configure the Cisco IOS software to append RIF information use the following command in interface configuration mode Command Purpose multiring protocol keyword all routes spanning all Enable collection and use of RIF other information For an example of how to configure the software to bridge routed protocols se
67. s or all routes explorers Note that some older IBM devices generate only all routes explorer packets but many newer IBM devices are capable of generating spanning tree explorer packets A spanning tree explorer packet is an explorer packet that is sent to a defined group of nodes that comprise a statically configured spanning tree in the network In contrast an all routes explorer packet is an explorer packet that is sent to every node in the network on every path Bridging and IBM Networking Configuration Guide Enable the Automatic Spanning Tree Function Forwarding all routes explorer packets is the default However in complicated source route bridging topologies using this default can generate an exponentially large number of explorers that are traversing the network The number of explorer packets becomes quite large because duplicate explorer packets are sent across the network to every node on every path Eventually each explorer packet will reach the destination device The destination device will respond to each of these explorer packets It is from these responses that the source device will collect the RIF and determine which route it will use to communicate with the destination device Usually the route contained in the first returned response will be used The number of explorer packets traversing the network can be reduced by sending spanning tree explorer packets Spanning tree explorer packets are sent to specific nodes that
68. server named FILESVR3 The following set of router configuration commands would meet this need netbios access list host MIS permit FILESVR3 netbios access list host MIS deny l access list 202 permit 0x0404 0x0001 Permits SNA frames command or response access list 202 permit 0x0004 0x0001 Permits SNA Explorers with NULL DSAP l access list 701 permit 0110 2222 3333 l interface tokenring 0 access expression in lsap 202 amp dmac 701 netbios host MIS Fast Switching Example The following example disables fast switching between two Token Ring interfaces in the same router Frames entering Token Ring interfaces 0 or 1 will not be fast switched to the other interface global command establishing the ring group for the interface configuration commands source bridge ring group 2 1 commands that follow apply to interface token 0 interface tokenring 0 enable srb between local ring 1 bridge 1 and target ring 2 source bridge 1 1 2 disable source route fast switching cache on interface token 0 no source bridge route cache I interface token 1 enable srb between local ring 2 bridge 1 and target ring 1 source bridge 2 1 1 no source bridge route cache Configuring Source Route Bridging BC 163 SRB Configuration Examples Autonomous Switching Example The following example enables use of autonomous switching between two ciscoBus Token Ring interfaces in the same router Frames entering Token Ring i
69. sociated with a ring that actually represents the entire transparent bridging domain To the transparent bridging station the bridge represents just another port in the bridge group When bridging from the SRB typically Token Ring domain to the transparent bridging typically Ethernet domain the source route fields of the frames are removed The RIFs are cached for use by subsequent return traffic When bridging from the transparent bridging domain to the SRB domain the router checks the packet to see if it has a multicast or broadcast destination or a unicast single host destination If it is multicast the packet is sent as a spanning tree explorer If it is a unicast destination the router looks up the path to the destination in the RIF cache If a path is found it will be used otherwise the router will send the packet as a spanning tree explorer An example of a simple SR TLB topology is shown in Figure 50 Configuring Source Route Bridging BC 119 Configure Translation between SRB and Transparent Bridging Environments BC 120 Figure 50 Example of a Simple SR TLB Topology Transparent bridging ring Transparent s Source route Router running bridging domain bridged domain SR TLB 1 1 1 Token Lo Ring y s Frames lose RIFs in this direction a Frames gain RIFs in this direction 1108a lt Note The Spanning Tree Protocol messages used to prevent loops in the tr
70. ssible To enable SR TLB you must perform the task in the following section Enable Bridging between Transparent Bridging and SRB In addition you can also perform the tasks in the following sections Disable Fast Switched SR TLB Enable Translation Compatibility with IBM 8209 Bridges Enable Token Ring LLC2 to Ethernet Conversion Enable Bridging between Transparent Bridging and SRB Before enabling bridging you must have completely configured your router using multiport SRB and transparent bridging Once you have done this establish bridging between transparent bridging and source route bridging by using the following command in global configuration mode Command Purpose source bridge transparent ring group pseudo ring Enable bridging between transparent bridge number tb group oui bridging and SRB Disable Fast Switched SR TLB To disable fast switched SR TLB and cause the router to handle packets by process switching use the following command in global configuration mode Command Purpose no source bridge transparent ring group fastswitch Disable fast switched SR TLB Enable Translation Compatibility with IBM 8209 Bridges To transfer data between IBM 8209 Ethernet Token Ring bridges and routers running the SR TLB software to create a Token Ring backbone to connect Ethernets use the following command on each Token Ring interface in interface configuration mode Command Purpose ethernet t
71. t LNM uses These routers provide all functions the IBM Bridge Program currently provides Thus LNM can communicate with a router as if it were an IBM source route bridge such as the IBM 8209 and can manage or monitor any Token Ring connected to the router Through IBM Bridge support LNM provides three basic services for the SRB network The Configuration Report Server CRS monitors the current logical configuration of a Token Ring and reports any changes to LNM CRS also reports various other events such as the change of an active monitor on a Token Ring The Ring Error Monitor REM monitors errors reported by any station on the ring In addition REM monitors whether the ring is in a functional or a failure state The Ring Parameter Server RPS reports to LNM when any new station joins a Token Ring and ensures that all stations on a ring are using a consistent set of reporting parameters IBM Bridge support for LNM also allows asynchronous notification of some events that can occur on a Token Ring Examples of these events include notification of a new station joining the Token Ring or of the ring entering failure mode known as beaconing Support is also provided for LNM to change the operating parameters in the bridge For a complete description of LNM refer to the IBM product manual supplied with the LNM program LNM support in our source route bridges is a powerful tool for managing SRB networks Through the ability to com
72. tBIOS packets To assign a byte offset access list name use the following command in global configuration mode Command Purpose netbios access list bytes name permit deny offset Define the byte offsets and patterns pattern within NetBIOS messages to match with access list parameters Note Using NetBIOS Byte Offset access filters disables the autonomous or fast switching of source route bridging frames When filtering by byte offset you can filter either incoming or outgoing messages on the interface To specify the direction use one of the following commands in interface configuration mode Command Purpose netbios input access filter bytes name Specify a byte based access filter on incoming messages Bridging and IBM Networking Configuration Guide Configure Administrative Filters for Token Ring Traffic Command Purpose netbios output access filter bytes name Specify a byte based access filter on outgoing messages Configure Administrative Filters for Token Ring Traffic Source route bridges normally filter frames according to the routing information contained in the frame That is a bridge will not forward a frame back to its originating network segment or any other network segment that the frame has already traversed This section describes how to configure another type of filter the administrative filter Administrative filters can filter frames based on the following methods P
73. tion of source route bridging enables you to connect two or more Token Ring networks using either Token Ring or Fiber Distributed Data Interface FDDI media The Cisco IOS software offers the ability to encapsulate source route bridging traffic using RFC 1490 Bridged 802 5 encapsulation This encapsulation provides SRB over Frame Relay functionality You can configure the Cisco IOS software for source route bridging by performing the tasks in one of the first three sections and optionally the tasks in the last section Configure a Dual Port Bridge Configure a Multiport Bridge Using a Virtual Ring Configure SRB over FDDI Configure Fast Switching SRB over FDDI Configure SRB over Frame Relay Enable the Forwarding and Blocking of Spanning Tree Explorers Enable the Automatic Spanning Tree Function Limit the Maximum SRB Hops Configure a Dual Port Bridge BC 110 A dual port bridge is the simplest source route bridging configuration When configured as a dual port bridge the access server or router serves to connect two Token Ring LANs One LAN is connected through one port Token Ring interface and the other LAN is connected through the other port also a Token Ring interface Figure 45 shows a dual port bridge Figure 45 Dual Port Bridge Token TO aoe Ring H J 129 S1102a To configure a dual port bridge that connects two Token Rings you must enable source route bridging on each of the Token R
74. uter either using SNMP or the proprietary IBM protocol some method is needed to prevent such changes from detrimentally interacting with each other You can prevent any LNM station from modifying parameters in the Cisco IOS software It does not affect the ability of LNM to monitor events only to change parameters on the router To prevent the modification of Cisco IOS software parameters by an LNM station use the following command in global configuration mode Command Purpose Inm snmp only Prevent LNM stations from modifying LNM parameters in the Cisco IOS software Enable Other LRMs to Change Router Parameters BC 130 LNM has a concept of reporting links and reporting link numbers A reporting link is simply a connection or potential connection between a LAN Reporting Manager LRM and a bridge A reporting link number is a unique number used to identify a reporting link An IBM bridge allows four simultaneous reporting links numbered 0 through 3 Only the LRM attached on the lowest numbered connection is allowed to change LNM parameters in the router and then only when that connection number falls below a certain configurable number In the default configuration the LRM connected through link 0 is the only LRM that can change LNM parameters Bridging and IBM Networking Configuration Guide Apply a Password to an LNM Reporting Link To enable other LRMs to change router parameters use the following command in interf
75. vailable locally through a particular interface netbios name cache mac address netbios name Define a static NetBIOS name cache entry ring group group number and specify that it is available remotely If you have defined a NetBIOS name cache entry you must also define a RIF entry For an example of how to configure a static NetBIOS entry see the NetBIOS Support with a Static NetBIOS Cache Entry Example section later in this chapter Specify Dead Time Intervals for NetBIOS Packets When NetBIOS name caching is enabled and default parameters are set on the router as well as the NetBIOS name server and the NetBIOS name client approximately 20 broadcast packets per logon are kept on the local ring where they are generated The broadcast packets are of the type ADD_NAME_QUERY ADD_GROUP_NAME and STATUS_QUERY Configuring Source Route Bridging BC 125 Configure LNM Support The Cisco IOS software also converts pairs of FIND_NAME and NAME_RECOGNIZED packets received from explorers which traverse all rings to specific route frames that are sent only between the two machines that need to see these packets You can specify a query timeout or dead time interval to prevent repeat or duplicate broadcast of these type of packets for the duration of the interval To specify dead time intervals use one or both of the following commands in global configuration mode Command Purpose netbios name cache query timeout
76. xample SRB over Frame Relay Configuration Example Figure 59 illustrates a network with the following characteristics Virtual Ring Number of Router A 100 Virtual Ring Number of FRAD B 200 Virtual Ring Number of FRAD C 300 DLCI number for PVC between Router A and FRAD B 30 DLCI number for PVC between Router A and FRAD C 31 Figure 59 FRAD Using SRB over Frame Relay to Connect to a Cisco Router Token Ring 10 Token Token Ring Ring a 20 30 B In this example we configure a new option conserve ring on the source bridge interface configuration command When this option is configured the SRB software does not add the ring number associated with the Frame Relay PVC the partner s virtual ring to outbound explorer frames This option is permitted for Frame Relay subinterfaces only The router configures the partner FRAD s virtual ring number as the ring number for the PVC This approach does not require a separate ring number per DLCI The router configures the partner FRAD s virtual ring number as the ring number for the PVC FRAD B would configure its virtual ring as 200 and the ring for the PVC as 100 FRAD C would configure its virtual ring as 300 and the ring for the PVC as 100 Configuring Source Route Bridging BC 151 SRB Configuration Examples Configuration of Router A source bridge ring group 100 l interface Seriall encapsulation frame relay l interface Seriall 1 point
77. xplorer Processing Configuration Example The following configuration example improves the handling of explorer frames enabling the Cisco IOS software to perform substantially better during explorer broadcast storms In this configuration the maximum byte rate of explorers is set to 100000 source bridge explorer maxrate 100000 source bridge explorerQ depth 100 no source bridge explorer fastswitch SRB Only Example The following example shows that all protocols are bridged including IP Because IP is being bridged the system has only one IP address no ip routing l interface tokenring 0 ip address 131 108 129 2 255 255 255 0 source bridge 129 1 130 source bridge spanning interface tokenring 1 ip address 131 108 129 2 255 255 255 0 source bridge 130 1 129 source bridge spanning l interface ethernet 0 ip address 131 108 129 2 255 255 255 0 Configuring Source Route Bridging BC 147 SRB Configuration Examples SRB and Routing Certain Protocols Example In the following configuration IP XNS and IPX are routed while all other protocols are bridged between rings While not strictly necessary the Novell IPX and XNS network numbers are set consistently with the IP subnetwork numbers This makes the network easier to maintain xns routing 0000 0C00 02C3 1 novell routing 0000 0C00 02c3 1 interface tokenring 0 ip address 131 108 129 2 255 255 255 0 xns network 129 novell network 129 source bridge 129 1 130 source

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