Exam 300-420 topic 1 question 175 discussion

Correct B

BGP Route Reflector (RR) system is a Client/Server System. All the BGP Route Reflectors are Server and the other iBGP peers are Client in this topology. BGP Route Reflectors are connected to all iBGP Peers and they learn the BGP routes form iBGP Peers, then they send this routes to orther iBGP Peers. Here, full mesh requirement is bypassed, all iBGP peers do not need to be connected eachother. So, the iBGP connections in a BGP topology is reduced. B. The route reflectors should be nonclients with regards to each other.

"However, since they use the same cluster, they discard the routes of each other." This article depicts the behavior of IBGP when the same clustering ID is used among 2 different router reflectors. Thus is can be deduced that if the route reflectors have the same cluster ID, and they are advertising routes to each other, they will drop the routes learned from each other. So A wouldn't work. https://orhanergun.net/bgp-route-reflector-clusters#:~:text=Route%20Reflector%20Cluster%20ID%20is,ID%20to%20the%20cluster%20list.

When configure multi-cluster of BGP RRs, RRs should peer with each RR as non-client according to CCIE routing TCP/IP volumn 2 @2001 page 127 - if the route was learned from nonclient IBGP peer, it is reflected to client only (here RR's route learnt from other RRs is able to reflect to its client) - if the route was learned from a client, it is reflected to all nonclients and clients, except for the originating client. (routes learnt within the cluster can reflect to nonclient, RR) - it the route was learnt from an EBGP peer, it is reflected to all nonclients and clients. BTW, bearing in mind that, all RRs should build fully mesh peering.

Update: Actually, the RR routers should be "iBGP" neighbors but they should have a RR server-client relationship Which means each RR router should see the other RR router as "route-reflector-client" Source (with timestamp): https://youtu.be/ofNX-9Hf7EE?list=PLJqb_j53o7BiVPaFGQxEHhGx-ximMukwH&t=616

Route reflectors should simply have a normal "iBGP peering" with eachother Answer B is incorrect, because if the RR routers are "non-clients" to eachother, they wouldnt redistribute their own Client's routes to their neighbor RR routers. (So answer B is incorrect) Now does "should be made dents of eachother" means they should simply be "iBGP" peers of eachother? Does cisco really have to throw in fancy words like these on an exam to give us even a harder time? It seems so. I would still go with Answer A, cause I would say it is the most that resembles a "normal iBGP peering between the RR routers"...