Cisco Systems BC-109 Manual De Usuario

Bridging and IBM Networking Configuration Guide

To take advantage of this virtual ring feature, each Token Ring 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:

Define a ring group.

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.

Ring numbers need to be unique across interfaces and networks.

Define a Ring Group in SRB Context

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 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:

source-bridge ring-group ring-group 
[virtual-mac-address]

Define a ring group.

no source-bridge ring-group ring-group 
[virtual-mac-address]

Remove a ring group.

S2324

T1

T0

T2

T3

Token

Ring

Token

Ring

Token

Ring

Token

Ring