[dns-operations] Unpublished IP addresses for Google Public DNS

[Robert Edmonds]

Babak Farrokhi wrote:
> I believe it is safe to assume that documentation might be outdated or inaccurate.
> I’ve been probing this for a while using RIPE Atlas network around the world and sending queries like this:
> 
> dig +short TXT maxmind.test-ipv6.com @8.8.8.8
> 
> It returns the IP address AS number from which the resolver sends a query (should be one of those IP addresses Google published). There has been several cases that IPs belonged the Google (AS15169) but was not in the list you mentioned.  And it turned out there are operators around the world who redirect DNS traffic toward their own resolvers (like 2% of responses were coming from IP addresses did not belong to Google).

There's also test.dns.google.com./TXT, which should return the TXT
record "Thanks for using Google Public DNS." if the query is served by
Google Public DNS, and NXDOMAIN otherwise.

-- 
Robert Edmonds