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Cisco Catalyst 5000 Series Switches

Token Ring Inter-Switch Link Configuration Guide

Cisco - Token Ring Inter-Switch Link Configuration Guide

Introduction

This configuration guide explains how to configure IP/IPX in a Token Ring environment.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.

Configurations

This document uses these configurations:

Configuring Simple IP/IPX Routing for Token Ring Inter-Switch Link

The first step in any Token Ring Inter-Switch Link (TRISL) configuration is to make sure that the correct configuration for virtual LANs (VLANs) exist in the switched network. When routing IP, you can have a network with or without a Routing Information Field (RIF). Depending on how you configured the stations in your network, you might need multiring in the routers. If you do, you might need to create additional VLANs.

This is an example in a non-RIF IP network:

tr-isl-conf1.gif

Complete these steps in order to create the VLANs in the Token Ring switched network:

  1. Enter this command to create the Token Ring bridge relay function (BRF) VLAN on the switched side of the network. This Token Ring BRF VLAN is the parent for the Token Ring concentrator relay function (CRF) VLANs that is assigned to the ports of the switch or switches in the network:

    set vlan 100 type trbrf name test_brf bridge 0xf stp ieee
  2. Create the Token Ring CRF VLANs. Because this is a non-RIF network, set the bridging mode between the Token Ring CRF VLANs and the Token Ring BRF to source-route transparent bridging (SRT) mode by entering these commands:

    set vlan 101 type trcrf name test_crf1 ring 0x100 parent 100 mode srt 
    
    set vlan 102 type trcrf name test_crf2 ring 0x200 parent 100 mode srt 
    
    set vlan 103 type trcrf name test_crf3 ring 0x300 parent 100 mode srt
  3. Check the spanning tree information. Enter the show spantree <vlan> command on the switches to make sure that the Token Ring CRF VLAN is set to Cisco spanning tree, and the parent is set to IEEE. If you require different values, check the Catalyst 5000 Token Ring blade home page for information on how to implement different spanning tree information.

  4. Assign the VLANs to the ports in the switch network.

    As an example, one CRF is assigned to all the ports in each switch so that one switch will be configured with VLAN 101, the next with VLAN 102, and so on. Once this is is done, you can establish IP connectivity throughout the switched network.

  5. Now, concentrate on the router side of the network. Create the subinterface of the Fast Ethernet port (the 2FE/ISL interface card) by entering this command:

    encapsulation tr-isl trbrf-vlan 100 bridge-num 15

    This command ties the subinterface of the router with the Token Ring BRF VLAN that was created in step 1. Because this network passes non-source routed (NSR) traffic, you do not need multiring functionality. You are finished configuring TRISL-specific parameters, and you can now configure the IP-related commands.

  6. If you wish to configure the router to support frame sizes larger than 1500 bytes, you must change the maximum transmission unit (MTU) of the subinterface using the mtu command. With the PA-2FE/ISL card, you can configure the MTU up to 18 KB for TRISL encapsulation subinterfaces.

    The same configuration rule applies for IPX supported by the TRISL VLAN. Simply configure the IPX network on the TRISL subinterface. The final configuration should look similar to this:

    interface FastEthernet6/0.1
    
       mtu 4472
    
       encapsulation tr-isl trbrf-vlan 100 bridge-num 15
    
       ip address 1.1.1.1 255.255.255.0
    
       no ip redirects
    
       ipx encapsulation SAP
    
       ipx network 1
    
       !

    You can create different Token Ring BRF and Token Ring CRF VLANs, and assign these to different ports on the switch to have different subnets and networks under the same ISL trunk.

Multiring Configuration for IP/IPX Routed Protocols

If there are multiple source-route bridges in your TRISL network, you need to add multiring functionality under the TRISL subinterface so the routing code can append RIF information to reach the network stations.

In an environment using multiring for regular Token Ring interfaces, the interface receiving the routed packets with RIF is a ring. In an environment using multiring for TRISL, the bridge itself is being extended from the switch to the router. Because of this, you must create an invisible ring that the multiring code appends to the RIF to complete the RIF. This invisible ring is called the psuedo-ring in the router.

Because all the switches in the network need to know how to reach all the rings in the switched network, the pseudo-ring needs to be known. You can accomplish this by assigning a Token Ring BRF VLAN in the router under the multiring code, and then creating a Token Ring CRF VLAN under that parent Token Ring BRF VLAN.

Complete these steps:

  1. Create the Token Ring BRF VLANs.

    As an example, a total of three Token Ring BRF VLANs are created:

    set vlan 100 type trbrf name test_brf1 bridge 0xf 
    
    set vlan 200 type trbrf name test_brf2 bridge 0xe 
    
    set vlan 300 type trbrf name test_brf3 bridge 0xd
  2. Create the Token Ring CRF VLANs.

    This example shows a total of two for each Token Ring BRF, one for the router and one for the switch:

    set vlan 101 type trcrf name test_crf1 ring 0x100 parent 100 
    
    set vlan 102 type trcrf name test_crf2 ring 0x200 parent 100 
    
    set vlan 201 type trcrf name test_crf3 ring 0x300 parent 200 
    
    set vlan 202 type trcrf name test_crf4 ring 0x400 parent 200 
    
    set vlan 301 type trcrf name test_crf5 ring 0x500 parent 300 
    
    set vlan 302 type trcrf name test_crf6 ring 0x600 parent 300

    Name the CRFs of the router as "router_crf" to avoid confusion when you assign the VLANs in the network.

  3. Now it is time to assign the VLANs to the different switches.

    In this example, VLAN 101, 201, and 301 are assigned to all the ports of each respective switch.

  4. On the router, create a subinterface with TRISL encapsulation for each of the Token Ring BRF VLANs that you created.

    This example is from the router's configuration:

    ! 
    
    interface FastEthernet6/0.1 
     encapsulation tr-isl trbrf-vlan 100 bridge-num 15 
    ! 
    
    interface FastEthernet6/0.2 
     encapsulation tr-isl trbrf-vlan 200 bridge-num 14 
    ! 
    
    interface FastEthernet6/0.3 
     encapsulation tr-isl trbrf-vlan 300 bridge-num 13 
    !
  5. Add the multiring command to the subinterfaces of the router.

    ! 
    
    interface FastEthernet6/0.1 
    
    encapsulation tr-isl trbrf-vlan 100 bridge-num 15 
    
    multiring trcrf-vlan 102 ring 0x200 
    
    multiring all 
    
    !

    This command specifies which VLAN is assigned as the multiring pseudo-ring and which is assigned to the ring that is actually there. The ring number is specified here because the router does not run Virtual Terminal Protocol (VTP) and cannot extract the ring number from the VLAN database created on the switch.

  6. Repeat this process for each Fast Ethernet subinterface on the router. In addition, if you want the router to handle larger frame sizes, you must change the MTU under each of the subinterfaces of the router. With the PA-2FE/ISL card, you can go up to 18 KB frame sizes.

    Once this is accomplished, add the IP addresses and IPX networks for each of the subinterfaces to the router configuration. The router's Fast Ethernet configuration should look similar to this:

    !
    
    interface FastEthernet6/0.1
     mtu 4472
     encapsulation tr-isl trbrf-vlan 100 bridge-num 15
     ip address 1.1.1.1 255.255.255.0
     no ip redirects
     ipx encapsulation SAP
     ipx network 1
     multiring trcrf-vlan 102 ring 0x200
     multiring all
     !
    
    interface FastEthernet6/0.2
     mtu 4472
     encapsulation tr-isl trbrf-vlan 200 bridge-num 14
     ip address 1.1.2.1 255.255.255.0
     no ip redirects
     ipx encapsulation SAP
     ipx network 2
     multiring trcrf-vlan 202 ring 0x400
     multiring all
     !
    
    interface FastEthernet6/0.3
     mtu 4472
     encapsulation tr-isl trbrf-vlan 200 bridge-num 13
     ip address 1.1.3.1 255.255.255.0
     no ip redirects
     ipx encapsulation SAP
     ipx network 3
     multiring trcrf-vlan 302 ring 0x600
     multiring all
     !

    Note: Be careful when you change the MTUs of the PA-2FE/ISL card in the Cisco 7500 series routers. This can cause an MEMD buffer recarve.

Source-Route Bridge Configuration

In order to configure source-route bridging for TRISL, you need to tie the TRISL interface to the virtual ring of the router. (You cannot point the TRISL interface to another interface of the router as a two port bridge.) Because the switched network must know about the next hop VLAN in the network, a Token Ring CRF VLAN that matches the parameters of the virtual ring in the router is created.

This is similar to the principles applied in multiring functionality. Therefore, a similar configuration is applied.

  1. Create the Token Ring BRF VLANs by entering these commands:

    set vlan 100 type trbrf name test_brf1 bridge 0xf 
    
    set vlan 200 type trbrf name test_brf2 bridge 0xe 
    
    set vlan 300 type trbrf name test_brf3 bridge 0xd
  2. Now create the Token Ring CRF VLANs that will be assigned to the BRF VLANs. Assign each VLAN a unique VLAN ID. Note, you need to assign the virtual ring ID in the router to the CRF that is a virtual ring under a BRF:

    set vlan 101 type trcrf name test_crf1 ring 0x100 parent 100 
    
    set vlan 102 type trcrf name test_crf2 ring 0xfff parent 100 
    
    set vlan 201 type trcrf name test_crf3 ring 0x300 parent 200 
    
    set vlan 202 type trcrf name test_crf4 ring 0xfff parent 200 
    
    set vlan 301 type trcrf name test_crf5 ring 0x500 parent 300 
    
    set vlan 302 type trcrf name test_crf6 ring 0xfff parent 300

    The assignment of the VLANs should look similar to this diagram:

    tr-isl-conf2.gif

  3. Make sure that the virtual ring of the router is 4095 (0xFFF):

    source-bridge ring-group 4095
  4. Add the TRISL subinterface commands on the Fast Ethernet interface:

    ! 
    interface FastEthernet6/0.1 
     mtu 4472 
     encapsulation tr-isl trbrf-vlan 100 bridge-num 15 
     !

    Repeat these steps for all the Token Ring BRF VLANs you created using their respective information.

  5. Add the source-route bridge configuration. Because the bridge number is already known (in the encapsulation tr-isl command), tie the Token Ring CRF of the router with the ring group.

    ! 
    interface FastEthernet6/0.1 
     encapsulation tr-isl trbrf-vlan 100 bridge-num 15 
     source-bridge trcrf-vlan 102 ring-group 4095 
     source-bridge spanning 
     !

    Note: If you do not adjust the MTU of the TRISL subinterface, when RIFs pass through the router, the maximum packet size in the RIF/RC is reduced to 1500 bytes. You can adjust the MTU on a subinterface basis. However, be mindful of the cBus buffer recarve in the Cisco 7500 series routers.

Combining Multiring and Source-Routed Traffic

When you configure TRISL in a situation where you have both multiring and source-routed traffic, you only need one VLAN per parent Token Ring BRF. You can use the same VLAN for both multiring and source-route bridging purposes. However, each parent Token Ring BRF must have the same ring number.

  1. Create the parent BRF VLAN (see the Source-Route Bridge Configuration example).

  2. Create the children CRF VLANs (see the Source-Route Bridge Configuration example). Make sure that all the CRF VLANs have the same ring number, that of the virtual ring of the router.

  3. Now add the source-route bridging commands.

  4. Create a multiring statement for each subinterface using the same VLAN as the one for source-route bridging and the multiring command. Each command should have a unique VLAN number, but the ring number should be the same.

    The configuration should look similar to this:

    ! 
    
    interface FastEthernet6/0.1 
     mtu 4472 
     encapsulation tr-isl trbrf-vlan 100 bridge-num 15 
     ip address 1.1.1.1 255.255.255.0 
     no ip redirects 
     ipx encapsulation SAP 
     ipx network 1 
     multiring trcrf-vlan 102 ring 4095 
     multiring all 
     source-bridge trcrf-vlan 102 ring-group 4095 
     source-bridge spanning 
     ! 
    
    interface FastEthernet6/0.2 
     mtu 4472 
     encapsulation tr-isl trbrf-vlan 200 bridge-num 14 
     ip address 1.1.2.1 255.255.255.0 
     no ip redirects 
     ip encapsulation SAP 
     ipx network 2 
     multiring trcrf-vlan 202 ring 4095 
     multiring all 
     source-bridge trcrf-vlan 202 ring-group 4095 
     source-bridge spanning 
     ! 
    
    interface FastEthernet6/0.3 
     mtu 4472 
     encapsulation tr-isl trbrf-vlan 300 bridge-num 13 
     ip address 1.1.3.1 255.255.255.0 
     no ip redirects 
     ipx encapsulation SAP 
     ipx network 3 
     multiring trcrf-vlan 302 ring 4095 
     multiring all 
     source-bridge trcrf-vlan 302 ring-group 4095 
     source-bridge spanning 
     !

Related Information

Updated: Sep 09, 2005
Document ID: 12988