BGP: Route Reflectors

Route Reflectors accomplish the same goal as Confederations in that they remove the need for a full mesh of iBGP Peers, allow all iBGP routes to be learned by all iBGP routers i nthe AS, and prevent loops.

There are RR servers and RR clients, these servers learn all iBGP routes from their clients then advertises all iBGP routes to all other RR client peers.

Only the RR uses modified rules, other routers clients and nonclients are not even aware of the RR nor do they change their operating rules.

RR design can include clusters withe multiple RRs in a cluster or multiple clusters.

Typically all RRs are peered directly, and in multiple clusters at least one peering needs to be established to each cluster for route sharing.

RRs use several tools to prevent routing loops including:

  • CLUSTER_LIST: RRs add their cluster ID into a BGP PA before sending an update.  RRs will drop any updates that include their own cluster ID.
  • ORIGINATOR_ID: This PA lists the RID of the first iBGP peer to advertise the route into the AS, if the router sees its own originator id it does not use or propagate that route.
  • Only advertise best routes: Only routes considered ‘best’ routes are reflected.

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