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I'm looking to do a small multi-homing setup which is currently achieved, with IPv4, using NAT. NPTv6 seems to be a good way to do this for IPv6 however I cannot find how to configure this on Cisco IOS.

Can anyone provide any insights into the IOS version required and the configuration commands?

phil-lavin
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    I don't think that sounds like a good way to do it. Any solution involving NAT66 sounds like a misunderstanding of the problem to be solved. Instead I'd go with each host having two addresses, one from each prefix. – kasperd Mar 23 '15 at 17:31
  • @kasperd - I did consider that but research suggests that it's a tricky exercise to have the router monitor the state of the connection and revoke IP addresses from the devices in the case that a link goes down. Can you suggest a simple way to do this? – phil-lavin Mar 23 '15 at 18:30
  • Ideally clients would automatically try each of their IPv6 addresses when connecting to remote servers, such that there isn't any need to revoke the IP addresses when a link goes down temporarily. However, I don't know how well clients deal with that. – kasperd Mar 23 '15 at 18:51
  • I just tested Chromium on Ubuntu 14.04. It is not doing well. I gave it a hostname which I deliberately had resolve to an invalid IP (2001:db8::2). My hope was that it would attempt connecting using different local addresses (I have three global unicast addresses on a single interface). It did attempt two TCP connections in parallel, but both used the same local address. I wonder if other client software is better at dealing with dual homing. – kasperd Mar 23 '15 at 19:00
  • Thanks for trying it out. It does sound theoretically possible. To be honest, I'd be happy if it looked for an A record when unable to communicate with the IP defined in the AAAA record as none of our services are solely IPv6. Windows doesn't do this, though. – phil-lavin Mar 23 '15 at 19:11
  • Are you suggesting Windows doesn't have Happy Eyeballs? (I couldn't test myself, I am not a Windows user.) – kasperd Mar 23 '15 at 19:49
  • Either way, to me it sounds like you would be using NPTv6 as a workaround for client shortcomings. That certainly goes against the principle about putting intelligence on the endpoints and keeping the intermediate network simple. But I suppose sometimes a temporary workaround may be needed if the root problem cannot be immediately fixed. – kasperd Mar 23 '15 at 19:53

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