On Oct 26, 2009, Andrew G. Malis wrote: > Note that IPv6 NAT makes multihoming to different ISPs much easier as > well. > > One thing that IPv6 NAT has in advantage to IPv4 NAT is that it can be > stateless, isomorphic, and port transparent [...] Right. There is one limitation, though: With stateless NAT'ing alone, failover of active communication sessions between providers is not possible. This is because statelessness requires one-to-one address mappings, hence a separate internal prefix for every provider-assigned external prefix. Many-to-one address mapping, such as by mapping a single internal prefix onto multiple external prefixes, would require stateful demultiplexing. You can avoid above limitation with some support in the routing system. [1] describes this. It comes at a cost, however: It requires selective route announcements internally in lieu of a default route, as well as redirects of incoming communication sessions. - Christian [1] http://christianvogt.mailup.net/pub/2008/vogt-2008-six-one-router-design.pdf _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf