IPv6 routing /48s

Florian Weimer fw at deneb.enyo.de
Fri Nov 21 15:55:42 UTC 2008

* Mohacsi Janos:

> On Thu, 20 Nov 2008, Nathan Ward wrote:
>> On 20/11/2008, at 4:06 AM, Florian Weimer wrote:
>>> * Michael Sinatra:
>>>> And it just reinforces the fear that people have against putting AAAA
>>>> records in DNS for their publicly-accessible resources, especially
>>>> www.
>>> Won't current Windows clients work just fine in this case?
>>> I have no idea what a fix should look like for some of the non-Windows
>>> systems I care about, unfortunately.

Do you mean that the client tries to enable 6to4 unsuccessfully?

>> No, unfortunately broken 6to4 auto-configuration (ie, in Vista,
>> XPSP2, when on a non-RFC1918 IP address) breaks, and you get 90s
>> timeouts before falling back to IPv4/A.
> This must be a broken RFC 3484 implementation:
> - 6to4 should be less prerefed than IPv4 if the service has both AAAA
> and A record.

RFC 3848 generally prefers IPv6 over IPv4 and fails if the host
running its algorithm has neither IPv6 connectivity nore mean to
detect that efficiently.  I think Windows does something in the second

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