Introduction to BGP Route Reflectors

BGP Route Reflectors

BGP is one of the most important and widely used protocol for connecting the devices between two different organizations having different AS numbers. BGP has two variants "iBGP and eBGP". 

You can use BGP internally as well as iBGP protocol and in this article we are going to discuss on the concept of BGP route reflectors which resolves the iBGP full meshed topology or you can say BGP route reflector is an another solution for the explosion of iBGP peering within the AS. 

Why iBGP should be fully meshed ?
iBGP neighbors do not add their AS number to the AS_PATH when sending updates. So if they are not then how they avoid looping inside. Here the rule comes into the picture named " BGP split Horizon" and it states as Any routes learnt from an iBGP neighbor must never be advertised to any other iBGP neighbor and so they need full mesh environment to get the update.

⭐ Note : We are talking about iBGP which is working within the AS not the eBGP and route reflector is a solution to avoid full mesh between the iBGP peers.

Here in the topology shown above, the routers NDNA_R5, NDNA_R6 and NDNA_R7 forms a cluster, and NDNA_R5 is the Route Reflector. 

Routers NDNA_R2, NDNA_R3 and NDNA_R4 forms a second cluster, of which NDNA_R2 is the Route Reflector. 

Router NDNA_R1 is a kind of another cluster.
Fig 1.1- BGP Route Reflectors

⭐ Note: The routers NDNA_R1, 
NDNA_R2 and NDNA_R5 are fully meshed ( iBGP rule) and the routers within a cluster are not fully meshed ( act as Route Reflector)

    Configurations on NDNA_R2 (Route Reflector)

    Configurations on NDNA_R5 (Route Reflector)