Subject: RE: Non-existing DNS servers on windows

RE: Non-existing DNS servers on windows

From: Bert Belder <>
Date: Fri, 21 Oct 2011 09:42:40 -0700

> On Thu, Oct 20, 2011 at 03:35:33PM -0700, Bert Belder wrote:
> > Windows always reports some hard-coded IPv6 DNS servers that don't
> > actually exist. I see three of them, they're all prefixed with
> > fec0:0:0:ffff. This often doesn't hurt, but it does hurt when these
> > rogue nameservers end up at the top of the server list, because c-ares
> > first tries all of them before it moves on to something that does work.
> They're not rogue; they're intended for IPv6 anycast DNS service. The RFC
> question is expired, though, and these days, DHCPv6 is probably the most
> common way of configuring DNS for IPv6.
> I didn't think they came in the list if you actually had any other DNS
> (e.g., via DHCPv6), but I might be mistaken.

I can probably configure my own network such that these DNS servers are not
reported any more, but I don't want to tell all my users to do that. C-ares
should just try to not use these DNS servers; we should either put them at
the end of the list or ignore them altogether.

- Bert
Received on 2011-10-21