You use the neighbor route-reflector-client command to configure a BGP peer as a route-reflector client from the device that is going to reflect the routes (the route reflector).
Multiple route reflectors should belong to the same cluster. You can use the cluster-id command to change the device ID.
The route-reflector client reflects the routes as follows:
If route-reflector clients are connected in a full IBGP mesh, you can use the no client-to-client-reflection command to disable client-to-client reflection on the route reflector
A BGP device advertises only preferred routes that are installed in the Routing Table Manager (RTM). When a route cannot be installed in the RTM because the routing table is full, the route reflector may not reflect that route. You can use the always-propagate command to configure the route reflector to reflect routes that are not in the RTM.