EBGP peers exchange EBGP routes to other EBGP peers as well as IBGP peers. IBGP peers do not exchange routes received from one IBGP peer to another. So this requires that all your IBGP routers be fully meshed. This is not a scalable solution when the number of BGP routers in your AS becomes large (n BGP routers will require n*(n-1)/2 IBGP connections)
Router reflector is one solution to this problem. You configure one of the IBGP routers as a RR, and it will "reflect" routes coming from one peer to another as long as those peers are its clients.
HTH
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus
