Is it possible to specify a fallback NS?

Barry Margolin barmar at
Tue Oct 24 01:14:06 UTC 2006

In article <ehj6so$2g8p$1 at>,
 linuxnewbie1234 <linuxnewbie1234 at> wrote:

> Suppose I have a company ONE for which I am serving the domain
> I know the A addresses of a computer like
> however my company recently splitted and now there is an independent 
> branch, which is  .
> At TWO-ONE They have their computers (e.g., and their 
> NS which is . All the IP addresses can change without 
> them informing me. In addition they can split further and make a 
> THREE-ONE branch with the domain . TWO-ONE will be 
> informed of the split but not me.
> Since I have the top level NS BUT I don't have control on 
> what the other people do, is there a way to configure my zone file so 
> that for everything of the form it first goes looking in my 
> zone file and then if this finds nothing, either
> -goes asking recursively to OR
> -tells the client to refer to
> ?

Delegate the subdomain to their nameservers.

> Note that I cannot simply put an NS entry specifying NS 
> because if they split again forming "three" I wouldn't 
> catch that one. I really want a fallback on if the 
> computer is not found in my zone. Is that possible?

No, it's not possible with BIND.

Why would a branch called TWO be creating another subdomain called 
THREE?  If the new branch is part of TWO, it should be something like -- the DNS hierarchy should mirror the administrative 
hierarchy.  If it's a new, independent branch, like TWO was, then you 
should go through the same process to add it to your DNS hierarchy as 
you did when TWO was created.

Barry Margolin, barmar at
Arlington, MA
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