RFC 2991 (rfc2991) - Page 1 of 9
Multipath Issues in Unicast and Multicast Next-Hop Selection
Alternative Format: Original Text Document
Network Working Group D. Thaler
Request for Comments: 2991 Microsoft
Category: Informational C. Hopps
NextHop Technologies
November 2000
Multipath Issues in Unicast and Multicast Next-Hop Selection
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
Various routing protocols, including Open Shortest Path First (OSPF)
and Intermediate System to Intermediate System (ISIS), explicitly
allow "Equal-Cost Multipath" (ECMP) routing. Some router
implementations also allow equal-cost multipath usage with RIP and
other routing protocols. The effect of multipath routing on a
forwarder is that the forwarder potentially has several next-hops for
any given destination and must use some method to choose which next-
hop should be used for a given data packet.
1. Introduction
Various routing protocols, including OSPF and ISIS, explicitly allow
"Equal-Cost Multipath" routing. Some router implementations also
allow equal-cost multipath usage with RIP and other routing
protocols. Using equal-cost multipath means that if multiple equal-
cost routes to the same destination exist, they can be discovered and
used to provide load balancing among redundant paths.
The effect of multipath routing on a forwarder is that the forwarder
potentially has several next-hops for any given destination and must
use some method to choose which next-hop should be used for a given
data packet. This memo summarizes current practices, problems, and
solutions.
Thaler & Hopps Informational