IPv6 teredo blackout June 8th

Tore Anderson tore.anderson at redpill-linpro.com
Wed Feb 2 20:49:11 CET 2011

Hi Phil,

> Some windows platforms have teredo enabled by default.
> AAAA is preferred over A.
> That would indicate all IPv6 traffic would be preferred through the
> teredo tunnel with obvious capacity and relay throughput issues suddenly
> with no way of controlling the customer subs once the DNS entry comes up.

Teredo is nothing to worry about in conjunction with World IPv6 day.
Windows won't even ask for AAAA records if the only IPv6 connectivity it
has is Teredo (and if it has something else as well, it'll use that
instead). Furthermore, Teredo->IPv6 is preferred below IPv4->IPv4 in
Windows' system resolver.

It's pretty much only old versions (<10.50) of the Opera web browser
running on Windows that will prefer to use Teredo to connect to a
dual-stacked web site. And a handful of loonies using Miredo on OS
X/Linux/BSD, but who cares...

See also:


Best regards,
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com/
Tel: +47 21 54 41 27

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