Which DNS servers are people using?

[kasperd]

On the tunnel page there is only a single IPv6 address listed, which is 2001:470:20::2. What does people use as their secondary DNS server in case that one does not respond?

One option is to use 74.82.42.42 as the second DNS server. But if I am using the closest tunnel server, then 2001:470:20::2 and 74.82.42.42 are just two different IPs of the same DNS server, and if it goes down, it won't respond on either IP.

Another option is to use a DNS server from another provider as the secondary, but at this time I don't know another public DNS server which is whitelisted with Google. After the 6th of June I am going to use another provider for my secondary DNS server.

Until then what I have done so far is to find the unicast addresses of some of the DNS servers handling the 2001:470:20::2 anycast address. So now I know that 2001:470:0:69::2 and 2001:470:0:11e::2 are two of the HE DNS servers in Europe.

Does anybody know of a better option than configuring a couple of the unicast addresses?

[kasperd]

I created a couple of domain names that anybody can use to find the unicast IPv6 address of their DNS server.

dig -t aaaa mydnsv6.kasperd.net
dig -t aaaa mydnsv6-6to4.kasperd.net

If the DNS server has both a 6to4 address and a native IPv6 address, the two should return the two IPv6 addresses of the server.
If the DNS server has only one IPv6 address the two domain names will return the same IPv6 address.
If the DNS server does not have IPv6 at all, both domain names will return server failure.