Use of Route-Reflector in ISP's BGP core

Question

Why ISP's deploy RR in BGP core design and what can be done to ensure traffic patterns never traverse the RR router?

Answer 1

RR is deployed to reduce the number of IBGP connections among IBGP routers in one AS. RR design is much more simpler to configure compared to BGP confederation.

http://packetpushers.net/bgp-rr-design-part-2/

http://packetpushers.net/bgp-rr-design-part-1/

Answer 2

BGP requires that all iBGP speakers be fully meshed. However, this requirement does not scale well when there are many iBGP speakers. Instead of configuring a confederation, you can reduce the iBGP mesh by using a route reflector configuration.

A route reflector is a BGP router that is allowed to break the iBGP loop avoidance rule. Route reflectors can advertise updates received from an iBGP peer to another iBGP peer under specific conditions.

By breaking the rules, route reflectors are used to eliminate the full mesh requirement and allow for building iBGP networks that scale easily and cleanly.

https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/200153-BGP-Route-Reflection-and-Multiple-Cluste.html