IPv4/v6 DNS Clients

[foxpaws]

Hey folks, I had a random question I was a little curious about. I've finally gotten DNS and things working (including reverse DNS) for my tunnel. Since I had all that going, I went ahead and requested AAAA glue from network solutions for my domain. I am curious though, what happens when an IPv6/v4 client queries DNS and finds that my tunnel is down? Will it fall back to the IPv4 address for the nameservers, or will it continue to try all the IPv6 addresses and fail out without trying any of the v4 addresses? I understand it likely depends on the implementation of the DNS resolver, I was just looking for a generic case.

In case it matters, I have 3 ns servers listed for my domain, the first two (ns1 and ns2) will have AAAA glue, and the third will not. Since ns1 and ns2 will be on tunnels hosted by tunnelbroker, it's possible (even if unlikely) that both tunnels go down.

[xamiel]

The IPv4 nameserver will answer if the IPv6 nameservers go down. Thats the point of naming more than 1 nameserver. Redundancy.
Just to verify this, and you could do the same, I firewalled incoming udp traffic destined for the IPv6 address on port 53 of my nameserver.
It still answered queries on the v4 address and this was verified via logs. Take care. :)