BGP Multipath in Inter-AS Option-B

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Last updated 2018-04-19 (latest revision 2017-09-11)
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By default, The Border Gateway Protocol, BGP only installs the best- path to the IP Routing Table. BGP multi-path is a well known feature that enables installation of multiple paths to the IP Routing Table. This is done to achieve load balancing while forwarding traffic. For a path to be eligible as a multi-path, certain criteria need to be fulfilled. Inter-AS VPNs are commonly deployed to span organizations across Service Provider boundaries. In this draft, we describe an issue relating to multi-path load balancing that can arise in an Option B Inter-AS Deployment. With the help of a representative topology, we illustrate the problem and then present two simple schemes as the solution to the problem. We also note as a matter of independent interest that the same underlying issue is applicable to deployments that employ next-hop-self behavior (implicit or explicit) downstream and the multi-path feature upstream.

Authors (
Arjun Sreekantiah (
Dhananjaya Rao (
Keyur Patel (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)