Router reflection is an alternative to confederations as a strategy to reduce IBGP meshing. BGP specifies that a BGP speaker cannot advertise routes to an IBGP neighbor if the speaker learned the route from a different IBGP neighbor. A route reflector is a BGP speaker that advertises routes learned from each of its IBGP neighbors to its other IBGP neighbors; routes are reflected among IBGP routers that are not meshed. The route reflector’s neighbors are called route reflector clients. The clients are neighbors only to the route reflector, not to each other. Each route reflector client depends on the route reflector to advertise its routes within the AS; each client also depends on the route reflector to pass routes to the client.
A route reflector and its clients are collectively referred to as a cluster. Clients peer only with a route reflector and do not peer outside their cluster. Route reflectors peer with clients and other route reflectors within the cluster; outside the cluster they peer with other reflectors and other routers that are neither clients nor reflectors. Route reflectors and nonclient routers must be fully meshed.
Clients and nonclients have no knowledge of route reflection; they operate as standard BGP peers and require no configuration. You simply configure the route reflectors.
Route reflectors advertise routes learned from:
Figure 43 illustrates a simple route reflection setup. Configured as a route reflector, Router Harvard reflects routes among its clients within Cluster 23: Routers Plymouth, Westford, and Acton. These route reflector clients see router Harvard and each other simply as IBGP neighbors. Router Newport in AS 325 and router Mason in AS 413 see router Harvard simply as an EBGP neighbor in AS 29.
Figure 43: Simple Route Reflection
 | Copyright © 2008, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |