6. Operation

When an RR receives a route from an IBGP peer, it selects the best path based on its path selection rule. After the best path is selected, it must do the following depending on the type of peer it is receiving the best path from:

1. A route from a Non-Client IBGP peer:

   Reflect to all the Clients.

2. A route from a Client peer:

   Reflect to all the Non-Client peers and also to the Client peers. (Hence the Client peers are not required to be fully meshed.)

An Autonomous System could have many RRs. An RR treats other RRs just like any other internal BGP speakers. An RR could be configured to have other RRs in a Client group or Non-client group.

In a simple configuration, the backbone could be divided into many clusters. Each RR would be configured with other RRs as Non-Client peers (thus all the RRs will be fully meshed). The Clients will be configured to maintain IBGP session only with the RR in their cluster. Due to route reflection, all the IBGP speakers will receive reflected routing information.

It is possible in an Autonomous System to have BGP speakers that do not understand the concept of route reflectors (let us call them conventional BGP speakers). The route reflector scheme allows such conventional BGP speakers to coexist. Conventional BGP speakers could be members of either a Non-Client group or a Client group. This allows for an easy and gradual migration from the current IBGP model to the route reflection model. One could start creating clusters by configuring a single router as the designated RR and configuring other RRs and their clients as normal IBGP peers. Additional clusters can be created gradually.