How to Configure BGP Route Reflection

By Walter J. Goralski, Cathy Gadecki, and Michael Bushong from JUNOS OS For Dummies, 2nd Edition

When you actually set up a router to act as a route reflector, the configuration of route reflectors must happen on both the route reflector and the client. Examine router 4’s clients.

Configure route reflection in a router

On the route reflector side, the configuration requires only that you identify the routing cluster for which the router is the reflector:

[edit protocols]
bgp {
  group reflector-peers {
   type internal;
   cluster 172.16.1.1;
   neighbor 172.16.2.2;
   neighbor 172.16.3.3;
   neighbor 172.16.4.4;
  }
}

The configuration is identical to a normal IBGP configuration except that a cluster ID is specified.

Notice in this configuration that the cluster ID is configured to be identical to the router ID. Use this configuration as a best practice because with it, you can more easily track the originating cluster for routes that are advertised throughout your network.

On the client side, the configuration is identical to previous IBGP configurations except that you now have only a session configured between each client and the route reflector (not between each other):

[edit protocols]
bgp {
  group route-reflector {
   type internal;
   neighbor 172.16.1.1;
  }
}

Each client to the route reflector will have that route reflector configured as an internal peer.

You still have to configure the routing policy to ensure that routes are advertised as expected. The route reflector doesn’t change that requirement.

You, however, don’t want to configure a next-hop-self policy on your route reflector because you don’t want all your externally bound traffic to flow through the route reflectors. You want it to take the shortest path, which isn’t generally through the route reflector. The exception to this rule is when the EBGP session from another AS is directly connected to your route reflector.