Yesterday's Windows update causes IPv4 to be default

Dan Wing dwing at
Thu Nov 15 16:36:31 CET 2012

> -----Original Message-----
> From: Sander Steffann [mailto:sander at]
> Sent: Thursday, November 15, 2012 1:49 AM
> To: Dan Wing
> Cc: 'Mike Jones'; 'Tassos Chatzithomaoglou'; ipv6-ops at
> Subject: Re: Yesterday's Windows update causes IPv4 to be default
> Hi,
> > The URL it tries to visit is, and
> > searching the Internet for that FQDN yields some details of how it
> > works.  If it can't retrieve the expected text at that URL, Windows
> > will order IPv6 to the bottom of its address preference table (by
> > tweaking its internal RFC3484 rules).  The success (or failure) to get
> > to that IPv6 site is remembered for that network for 30 days, and then
> > re-tested.  I don't know how to encourage it to try a fresh test, but
> > there must be a registry setting to force that to occur.
> WTF? So one failure (either locally or of a Microsoft webserver) causes
> an IPv6 outage of one month... It will be 'interesting' to see internet
> traffic patterns shift for a month when has an
> outage...

The stability of is quite good now.  I know of several
probes checking it frequently, from different locations.

> I think this is a *very* bad design decision.
> Sander


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