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oute reflector system has a set of client peers that are arranged in a cluster. The clients<br />

send their routes to the route reflector, and the route reflector advertises these<br />

routes to the other clients in the cluster and to other IBGP peers outside of the cluster<br />

(nonclient peers). The route reflector is not allowed to change any of the route’s<br />

attributes, which is one way of preventing routing loops. When the route reflector<br />

learns routes from nonclient peers, it advertises them to its clients and to no one else.<br />

For routes learned from EBGP, the route reflector follows normal BGP route advertisement<br />

rules, advertising these routes to both clients and nonclients.<br />

In this recipe, RouterG is the route reflector (see Figure 13-3). The only configuration<br />

needed is to add the cluster identifier to the IBGP group with the set cluster<br />

command. The cluster identifier is a 32-bit number. You can use the router identifier<br />

or any 32-bit number. When the router reflector forwards a route from one of its client<br />

routers to a nonclient router, the cluster identifier is prepended to the cluster list.<br />

If a route reflector ever receives a BGP update that contains its own cluster identifier,<br />

it ignores the update because it knows a routing loop has occurred.<br />

AS 65500<br />

RouterF<br />

192.168.16.1<br />

RouterD<br />

192.168.14.1<br />

AS 65505<br />

RouterE<br />

192.168.15.1<br />

RouterJ<br />

192.168.17.1<br />

RouterH<br />

192.168.18.1<br />

RouterC<br />

192.168.11.1<br />

Route reflector<br />

RouterG<br />

192.168.19.1<br />

Cluster<br />

RouterB<br />

192.168.12.1<br />

RouterA<br />

192.168.13.1<br />

Figure 13-3. Route reflector within the IBGP network<br />

This is the Title of the Book, eMatter Edition<br />

Copyright © 2008 O’Reilly & Associates, Inc. All rights reserved.<br />

Setting Up Route Reflectors | 453

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