[justinsaccount]

> DNS client IP is not the same as the real client IP

see https://developers.google.com/speed/public-dns/faq

"I've read claims that Google Public DNS can slow down certain multimedia applications or websites. Are these true?

...

To help reduce the distance between DNS servers and users, Google Public DNS has deployed its servers all over the world. In particular, users in Europe should be directed to CDN content servers in Europe, users in Asia should be directed to CDN servers in Asia, and users in the eastern, central and western U.S. should be directed to CDN servers in those respective regions. We have also published this information to help CDNs provide good DNS results for multimedia users.

In addition, Google Public DNS engineers have proposed a technical solution called EDNS Client Subnet. This proposal allows resolvers to pass in part of the client's IP address (the first 24/64 bits or less for IPv4/IPv6 respectively) as the source IP in the DNS message, so that name servers can return optimized results based on the user's location rather than that of the resolver. To date, we have deployed an implementation of the proposal for many large CDNs (including Akamai) and Google properties. The majority of geo-sensitive domain names are already covered.

"

[noponpop]

But that's google, I can tell you practically speaking many ISPs don't do this.

Client subnet extension would be very nice.