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

miken32
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Vikram Sisodia
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    Although this is old, this is better addressed to the [Network Stack Exchange](https://networkengineering.stackexchange.com). – tadman Mar 02 '18 at 03:41

2 Answers2

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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

Priya Gaikwad
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  • And to answer the last part of the questions: the route-reflectors don't change the BGP next-hop, so the next-hop will be resolved to the egress router, and not to the route reflector. The traffic will (normally) not flow through the route reflector. – Bruno Rijsman May 27 '21 at 06:54
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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/

Cisco Mmu
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