Subject: Re: 2.4.21+ - IPv6 over IPv4 tunneling b0rked
From: Andre Tomt <andre@tomt.net>
To: linux-kernel@vger.kernel.org
Cc: Mika Liljeberg <mika.liljeberg@welho.com>, netdev@oss.sgi.com
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Date: 11 Jul 2003 03:49:14 +0200
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On fre, 2003-07-11 at 02:04, Mika Liljeberg wrote:
> Well, the thing is that prefix:: is a special anycast address that
> identifies a router on the link prefix::/n, where n is the prefix
> length. You had configured a 127-bit link prefix, meaning that you had
> only one valid unicast address (last bit == 1) in addition to the router
> anycast address (last bit == 0).

Thanks for the explanation, I've been struggling to understand what
Yoshfuji tried to explain to me earlier on this topic (see "IPv6 bugs
introduced in 2.4.21" - ie. my bogus bugreport), now it all makes
perfect sense :-)

> Normally, IPv6 networks are supposed to use 64-bit on-link prefixes but
> the implementation can be written in such a way that other prefix
> lengths can be configured.
> 
> Setting your tunnel prefix to /64 is certainly the right thing to do. 

If you don't have anything but one /64 for example.. I guess /126's
would be ok as you could rule out the the anycast address? It will
probably work with Linux - but is it wrong in any sense, other than
"breaking" with EUI-64/autoconfiguration?

-- 
Cheers,
Andr? Tomt
andre@tomt.net

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