The graphic above illustrates a simple
IBGP configuration with three IBGP speakers (Routers A, B, and C).
Without route reflectors, when Router C receives a route from an
external neighbor, it must advertise it to both Routers A and B.
Routers A and B do not readvertise the IBGP learned route to other
IBGP speakers because the routers do not pass routes learned from
internal neighbors on to other internal neighbors, thus preventing a
routing information loop.
With route reflectors, all IBGP
speakers need not be fully meshed because there is a method to pass
learned routes to neighbors. In this model, an internal BGP peer is
configured to be a route reflector responsible for passing IBGP
learned routes to a set of IBGP neighbors. In the diagram above,
Router A is configured as a route reflector. When the route reflector
receives routes advertised from Router C, it advertises them to Router
B, and vice versa. This scheme eliminates the need for the IBGP
session between Routers B and C.
Your task in this lab is to configure
Router A as a route reflector since there is not a full IBGP mesh in
AS 100.