How to Configure Dual BGP Route Reflectors for Backup
Basic route reflection is fairly straightforward, but comes with a basic drawback. If you have only a single route reflector and that route reflector fails, your routers will be separated from your network, which means that you inadvertently created a single point of failure for that part of your network. To solve this problem, you can choose to configure dual route reflectors.
In this type of cluster, each client simply configures IBGP connections to both route reflectors. Each of the route reflectors configures its own cluster ID and forms peering relationships with its clients.
The two route reflectors themselves can interconnect in one of two ways: Either they can peer through a straight IBGP connection as per normal IBGP, or you can have each route reflector be a client to the other.
In the case where you have dual route reflectors, consider configuring each of them with exactly the same cluster ID. This configuration reduces the total number of routes that must be stored, and it tends to be far easier to understand when you depict the topology graphically (for example, the cluster has a single ID with two reflectors serving it).