multiple prefixes

Philipp Kern phil at
Wed Feb 13 16:01:02 CET 2013

On Tue, Feb 12, 2013 at 10:33:22AM -0800, Doug Barton wrote:
> | Every protocol that embeds literal IPv6 addresses (similar to the
> | situation with NAT64 and DNS64, except for v6) will break, unless it
> | tries to "discover" its global IP address somehow. That's reasonably
> | easy in the Skype world where there is central infrastructure.
> Right, solved problem.

Not solved for the software that cannot rely on such infrastructure.

> | BitTorrent, for instance, cannot reasonably do it.
> Um, it already does it, quite nicely. I've run bittorrent behind a
> double-NAT and I'm still able to get incoming connections.

Ironically what I've seen is Teredo for NAT traversal. Clients are
pushing lots of BitTorrent data over Teredo to users that have public
IPv6 behind a NAT. I was amazed by the bandwidth, too.

But right, there are different types of NAT and the one common with
firewall products doesn't allow hole punching.

> | So if you have one
> | behind NPT and one behind a stateful firewall you cannot get your
> | connections through.
> The firewall issue would need a solution of course, but can we please
> agree that anything related to the firewall is going to be the same
> whether dealing with NPT or GUAs?

Sure. I just mentioned it because it's the other side of the coin of
what NAT delivered. Two users behind NPT wouldn't work either.

Kind regards
Philipp Kern

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