Numbering nameservers and resolvers

Nick Olsen nick at
Tue Aug 17 19:00:11 UTC 2010

So lets say that you have multiple DNS resolvers in the same ip space that 
you advertise from multiple locations. All would be fine for the most part. 
But if you had a location equidistant network wise from two POP's wouldn't 
it load balance and possibly break some TCP sessions? How would someone get 
around this? This is also what OpenDNS does from what I understand.

Nick Olsen
Network Operations
(321) 205-1100 x106


From: "Doug Barton" <dougb at>
Sent: Tuesday, August 17, 2010 2:12 PM
To: "Sven Olaf Kamphuis" <sven at>
Subject: Re: Numbering nameservers and resolvers

On 08/17/2010 05:11, Sven Olaf Kamphuis wrote:
> tcp/zonetransfer not working reliably is no longer a problem

TCP is a MUST for DNS.

It's used as a fallback in the normal resolution process if an answer 
can't fit in a UDP packet for whatever reason. This is true even for 
common things like large A record lists, but is only becoming more 
frequent in the age of DNSSEC, AAAA, etc. It is unfortunately even more 
necessary than we had hoped it would be due to many local network 
operators not "getting the memo" regarding EDNS.




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