Route reflectors add an originator ID to each route that identifies the originator of the
route within the local AS by its router ID. If a router receives a route having the originator
ID set to its own router ID, it rejects the route.
You can also use a cluster list to prevent looping. Each cluster has an identifying number,
the cluster ID. For clusters with a single route reflector, the cluster ID is the router ID of
the route reflector; otherwise you configure the cluster ID. The cluster list records the
cluster ID of each cluster traversed by a route. When a route reflector passes a route from
a client to a nonclient router outside the cluster, the reflector appends the cluster ID to
the list. When a route reflector receives a route from a nonclient, it rejects the route if the
list contains the local cluster ID.
What about routes that a client forwards out of the cluster? No cluster ID is needed,
because clients can forward routes only to EBGP peers, that is, to peers outside the AS.
Looping between ASs is prevented by the AS-path list.
The following commands configure the route reflectors for the network topology shown
in Figure 46 on page 148. You configure the other routers, whether nonclients or route
reflector clients, as usual for IBGP and EBGP peers.
To configure router Salem as a route reflector:
host1(config)#router bgp 29
host1(config-router)#neighbor 10.2.5.5 remote-as 29
host1(config-router)#neighbor 10.2.5.5 route-reflector-client
host1(config-router)#neighbor 10.2.5.6 remote-as 29
host1(config-router)#neighbor 10.2.5.6 route-reflector-client
host1(config-router)#neighbor 10.2.5.7 remote-as 29
host1(config-router)#neighbor 10.2.5.8 remote-as 29
host1(config-router)#neighbor 10.2.25.5 remote-as 325
You do not configure a cluster ID, because router Salem is the only route reflector in this
cluster.
147Copyright © 2010, Juniper Networks, Inc.
Chapter 1: Configuring BGP Routing
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