Denic (.de) blocking 6to4 nameservers (since begin feb 2010)

Tim Chown tjc at
Tue Feb 16 14:00:13 UTC 2010

On Tue, Feb 16, 2010 at 08:14:13AM +0100, Mikael Abrahamsson wrote:
> On Tue, 16 Feb 2010, Nathan Ward wrote:
> >Perhaps they have Teredo and 6to4, and could not reach you via 6to4 so 
> >instead used Teredo, or, any number of scenarios.
> I think their only IPv6 connectivity was Teredo (for instance, they're 
> behind NAT), and thus they used it to get the IPv6 only content.

So for our case here at Southampton our web presence
is advertised via both A and AAAA records.

What we see is less than 1% of our IPv6 traffic coming from the Teredo
prefix.   6to4 is at most 1%.   I think the reason we see less 6to4 than
some might expect is that a lot of our IPv6 accesses may be from other
academic networks where IPv6 is available 'properly'.

I had our web guys send me a log of recent Teredo accesses to our servers
and the user agents were varied.    As Tore suggested, Opera 9.8 was
on the list (since fixed), but also some Mozilla-based entries from both
Linux and Windows platforms.

Total entries:  761
Opera 9.8:  354 
Firefox 3.5.7 (Windows):  61
Firefox 3.5.7 (Linux): 96
Iceweasel 3.5.6 (Linux): 8
Mozilla 4.0 (Windows): 242

Not a huge sample, but it shows Windows UAs hitting us from the Teredo


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