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There's a rumour that public domain name resolvers, like Google Public DNS, are still supposed to work with GeoDNS, because there's some field in the requests that lets them specify for which IP address they are doing a resolution, thus the authoritative servers can give a given resolver different resolutions for different final clients.

What's this whole thing called as far as RFCs go, and how does one mimic such resolutions, for testing purposes, e.g. with dig(1)? Else, what other tool is available to accomplish said task?

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3 Answers

There are google name servers all over the world and they use anycast routing so you will most likely get a name server physically close to where you are.

In addition google has introduced an extension to DNS called "Client Subnet in DNS Requests" http://tools.ietf.org/html/draft-vandergaast-edns-client-subnet-02 .

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Google usually serves from somewhere physically close, but not always. –  Michael Hampton Oct 25 '13 at 22:48
    
This is very interesting, probably exactly what I'm looking for; however, what common OSS is it implemented in? What are the options / dates / links to patches / tools for sample testing? I mean, it's not very clear how this whole thing is even to be referred as. –  cnst Oct 26 '13 at 1:19
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I use http://check-host.net for this.

Eg:

http://check-host.net/check-report/2b21cc

It runs your query from many different geographic locations.

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There's a very good description on the page below about how to set up a name server to work this way:

http://backreference.org/2010/02/01/geolocation-aware-dns-with-bind/

Long story short: based on the source IP address and based on some GeoIP databases you can set up rules to server different IP addresses for different countries or different regions.

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That doesn't work because the source IP will be the recursive resolver, not the client. A name server doesn't know the IP of the client that asked the recursive resolver to resolve a name. –  Mark Wagner Oct 25 '13 at 22:45
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