MPLS Labels and Devices

Hello Tanmoy

The Route Reflector (RR) used in MP-BGP within an ISP’s MPLS network is used in a similar way to it’s purpose within a regular BGP AS. Within an AS, iBGP requires that all iBGP routers have full mesh neighbor adjacencies. This means that in an AS with, say, 10 iBGP speakers, we’ll need N(N-1)/2 or 10*(10-1)/2 = 45 adjacencies. As AS networks increase, these adjacencies increase in number almost exponentially, which is a problem for scalability. The solution for this is an RR. The RR will collect all of the information about routes from all routers, and share this information with all the BGP routers in the AS. Although the mechanisms are different, the principle is similar to that of a DR for a network segment of an OSPF network. More information about RRs can be found at this lesson:

Although the above lesson focuses on conventional BGP AS’es, the principle is the same when applied to MP-BGP within an MPLS network.

I hope this has been helpful!