IPv6 6to4 and dns

Mark Andrews marka at isc.org
Thu Nov 18 19:06:49 CST 2010

In message <4CE5C820.5030205 at mompl.net>, Jeroen van Aart writes:
> What would be the best way to configure your dns once you've set up IPv6 
> 6to4? Separate the IPv4 and IPV6 domains or let them be the same?
> That is, use something like example.com for your existing IPv4 address 
> and something like 6.example.com for IPv6 (and www.6.example.com etc.)?
> Or is it safe to have both A and AAAA records for the same domain name?
> Thanks,
> Jeroen
> -- 
> http://goldmark.org/jeff/stupid-disclaimers/
> http://linuxmafia.com/~rick/faq/plural-of-virus.html

Firstly I would use a tunnel broker instead of 6to4.  Easier to
debug failures.

To answer your question you need to do a risk analysis.

Adding a IPv6 address next to a IPv4 address can make connections
to the site appear to be slow when the client side tries IPv6 but
doesn't have a working IPv6 path (this is a very small percentage).
There are some applications that will not fallback to IPv4 if the
IPv6 connection fails (this is also a small percentage again).

ISC publishes both AAAA and A record at the same name.  This is
somewhat of a forcing function for broken sites to address their
IPv6 issues.  We have been publishing both address for many years

Google on the other had decided to white-list sites that it knows
have IPv6 connectivity and a responsive noc.  6to4 sites don't meet
these requirments. Tunneled sites can.

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org

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