Hi Mike,
It has taken a while, but Google Public DNS IPv6 geographical coverage should now be comparable to coverage for IPv4.
Note that although the latency for DNS responses to cached data (frequently accessed domains like
www.google.com and many other non-Google ones) should now be comparable for IPv6 and IPv4, you may find that the answers (whether to AAAA (IPv6) or A (IPv4) queries) are different when you look up certain GeoIP-enabled domains via IPv6, e.g.:
204.237.142.160
204.237.142.155
54.192.19.202
54.192.19.81
54.192.19.93
54.192.19.13
54.192.19.67
54.192.19.41
54.192.19.130
54.192.19.6
This is a known issue in the ECS GeoIP configuration in the
DNSPod (
dnsv5.com) name servers used by
mi.com (
Xiaomi), which don't handle ECS with IPv6 client addresses correctly. Most larger (non-Chinese) CDNs will do the right thing, though:
104.117.60.111
104.117.60.111
If you re-enable IPv6 addresses for Google Public DNS, you may want to keep an eye out for problems like that, and if you (or other users of any resolvers that you point at Google Public DNS) use Chinese web sites extensively, you might want to stick to IPv4.
@alex