RFC 3178 (rfc3178) - Page 2 of 12
IPv6 Multihoming Support at Site Exit Routers
Alternative Format: Original Text Document
RFC 3178 IPv6 Multihoming Support at Site Exit Routers October 2001 o Obtain a portable IPv4 address prefix, and announce it from multiple upstream providers. o Obtain a single IPv4 address prefix from ISP A, and announce it from multiple upstream providers the site is connected to. Since the above two methodologies effectively inject additional routes to the worldwide routing table, they have negative impact on the worldwide routing table size issue. They also are not compatible with current IPv6 operational practice. This document provides a way to configure site exit routers and ISP routers, so that the site can achieve better reachability from multihomed connectivity, without impacting worldwide routing table size issues. The technique uses multiple distinct IPv6 address prefixes, assigned from multiple upstream ISPs. The technique uses an already-defined routing protocol (BGP or RIPng) and tunneling of IPv6 packets; therefore, this document introduces no new protocol standard (the document describes how to operate the configuration). This document is largely based on RFC 2260 [Bates, 1998] by Tony Bates. 2. Goals and non-goals The goal of this document is to achieve better packet delivery from a site to the outside, or from the outside to the site, even when some of the site exit links are down. Non goals are: o Choose the "best" exit link as possible. Note that there can be no common definition of the "best" exit link. o Achieve load-balancing between multiple exit links. o Cope with breakage of any of the upstream ISPs. 3. Basic mechanisms We use the technique described in RFC 2260 section 5.2 in our configuration. To summarize, for IPv4-only networks, RFC 2260 says that: o We assume that our site is connected to 2 ISPs, ISP-A and ISP-B. Hagino & Snyder Informational
