Route Reflection

Route reflection enables you to configure a BGP speaker as a route reflector which passes internally learned routes to a cluster of linked IBGP neighbors. The route reflector configured router advertises the routes it has learned from each linked client to the other linked clients in the AS. In a route reflection topology, the route reflector is the hub, and each client only peers with the hub. This eliminates the full mesh requirement. You can configure one or more routers in the AS to be reflectors. Some or all of the other routers for the AS are configured as clients. Route reflection is defined in RFC 4456.

Route reflection clients only peer with the route reflector. Route reflection configuration only occurs on the route reflector, identifying each route reflection client.

Multiple route reflectors can be configured in an AS. Multiple route reflectors can belong to a single route reflection cluster. A route reflection cluster is identified by a unique ID. If only a single route reflector is configured for an AS, the cluster ID defaults to the router ID of the route reflector.

See Autonomous System B of BGP Topology for a depiction of a route reflection topology.

Use the neighbor route-reflector-client command, in BGP configuration mode, to identify each client for the route reflection cluster.

The following example specifies that the neighbor 168.192.50.5 is a client of route reflector 1.1.1.1:

System(su-config)->router bgp 65151
System(su-config-bgp)->bgp router-id 1.1.1.1
System(su-config-bgp)->neighbor 168.92.50.5 remote-as 5
System(su-config-bgp)->neighbor 168.92.50.5 route-reflector-client

Use the bgp cluster-id command, in BGP configuration mode, to specify a unique route reflection cluster ID the route reflector(s) belong to.

The following example configures a cluster ID of 1.2.3.4 for router 1.1.1.1:

System(su-config)->router bgp 65151
System(su-config-bgp)->bgp router-id 1.1.1.1
System(su-config-bgp)->bgp cluster-id 1.2.3.4
System(su-config-bgp)->