Mac OS X IPv6 behaviour update
tore.anderson at redpill-linpro.com
Mon Sep 20 20:02:26 CEST 2010
I've managed to get hold of an OS X 10.6.5 beta (build 10H542) and play
a bit with it in my lab. It looks like Apple have been listening; the
IPv6 behaviour is much improved. Worth noting:
- 6to4 is no longer preferred over IPv4. I've tried both setting up a
local 6to4 interface on the OS X host, advertising an autoconf prefix
with RA, using both global and RFC 1918 IPv4 addresses on the Ethernet
interface, using Safari/Firefox/Chrome - and I've so far not been able
to reproduce any dualstack brokenness.
- The local 6to4 adapter now deactivates itself automatically when the
Ethernet interface is numbered with RFC 1918 addresses (unlike OS X
It's not 100% perfect though, some issues still remain:
- Teredo is still preferred over IPv4, at least when it is configured
with using SLAAC (OS X has no built-in support for Teredo, as far as I
- If OS X has a default IPv6 route, but only link-local addresses (for
example if it has received an RA without any prefix information),
Firefox fails to connect to dual-stack sites. tcpdump doesn't see any
IPv6 traffic on the wire though, so I'm not sure what's going on here.
Chrome and Safari handles the situation fine - they don't bother to ask
for AAAAs at all. In any case, this is an improvement over 10.6.4,
where Safari too had the same problem as Firefox still do.
I believe, however, that the vast majority of brokenness from the OS X
clients are caused by the 6to4 issues. OS X 10.6.5 is therefore likely
to have a very positive impact on the dualstack brokenness content
providers struggle with these days.
THANK YOU for fixing this, Apple! :-D
Now I'm just hoping that their update notification service is aggressive
enough to make most of their users upgrade to 10.6.5 shortly after it's
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