IPv6 6to4 and dns

Owen DeLong owen at delong.com
Fri Nov 19 01:34:17 CST 2010

On Nov 18, 2010, at 4:43 PM, Jeroen van Aart wrote:

> 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.)?
If you're going to use separate names for your AAAA, then the most common (least likely to confuse users) is ipv6.example.com vs. www.example.com.

> Or is it safe to have both A and AAAA records for the same domain name?
Depends on your value of safe. According to Google this will provide a poor user experience for 0.05% of the internet.
This 0.05% of the internet is the people who have broken IPv6 connectivity, but, hosts think they are IPv6 connected.

For HE, this has not been a significant problem and www.he.net has offered both A and AAAA records for years.
For Google, 0.05% represents significant revenue and customer lossage and they use separate names unless
your resolvers are whitelisted.

For more information on the exact problems, see Lorenzo's presentation at RIPE 61. He did an excellent job
of explaining the situation from Google's perspective.


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