Route Reflector Cluster
A BGP enabled router or BGP speakers. By default BGP speakers routers does not advertise iBGP-learned prefixes to iBGP peers routers - this has to be done to maintain loop prevention. RFC4456 introduces the route reflection feature which help to removes the need of full mesh configuration between iBGP speakers routers. When route reflector reflects a route, it creates and modifies an optional non-transitive attribute called CLUSTER_LIST by adding its own cluster ID to it. This attribute is used for loop prevention: when a BGP router receives update which CLUSTER_LIST contains router's own cluster ID, this update is discarded.
Route Reflector scalable alternative to an ibgp full mesh its allow a BGP speaker (route reflector –RR) to advertise route received from an ibgp peer to other ibgp peers.
note:client update server. Server update to all the remaining clients.
All client should establish neighbor with only servers . client will not establish neighbor with any other client. In case if you have 2 servers ( server establish neighbor with other servers and clients).
Route reflector clusters
A group of redundant route reflector and their clients from a cluster. Route reflector rules divide a transit AS into smaller areas (called clusters). Each BGP cluster must have a unique cluster-id. Every time a prefixe is reflected, the cluster-id is added to the cluster-id BGP attribute. The prefixe that already contains the local cluster-id in the cluster-list is not reflector
Note:Each cluster contain route reflectors and route reflector clients.
Lets see the configuration :-