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New in IPv6: The Next Chapter in IPv6 Multihoming Saga

Remember the IPv6 elephant in the room – the inability to do small-site multihoming without NAT (well, NPT66)? IPv6 is old enough to buy its own beer, but the elephant is still hogging the room. Tons of ideas have been thrown around in IETF (mostly based on source address selection tricks), but none of that spaghetti stuck to the wall.

A new draft by Jen Linkova and Massimiliano Stucchi tries to solve at least some aspects of this problem with conditional RA functionality: the lifetime of a PA IPv6 prefix is adjusted based on the status of the corresponding uplink.

Interestingly, I was musing along those same lines in 2010 but had to conclude the approach is impractical due to inability to deprecate an IPv6 prefix through RA. The new draft (if widely implemented in routers and hosts, which could take years) could solve that problem, finally resulting in reasonable IPv6 multihoming options.

New to IPv6?

The IPv6 webinars on are still pretty relevant (yeah, nothing much has changed in the meantime).


  1. Failover based on RA, how great is that. RFC 1925 has struck once again. What will be next?

  2. Multipath TCP is the right approach to solve multihoming problems from an architectural viewpoint. We should stop having single path transport protocols whose connections are bound to one particular IP address.

    1. Hi namesake. I think you don't unterstand the problem described in this post. You would get 2 PA address ranges because you were multihomed but you don't run BGP with your service providers. Instead you run DHCPv6 PD with them. So your servers would get 2 IPv6 addresses from every prefix. So the one billion dollar question is now how do you deal with a failure between you and and your service provider with that scenario?

  3. I was wondering why enterprise cant have dedicated block of IPv6 address and ISP's route the traffic to it. Enterprise shall select the ISP's based on the routing and preferences configured? If any looping has to be avoided then EVPN kind of solution can be used?


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