Is it possible to specify a fallback NS?

[Barry Margolin]

In article <ehj6so$2g8p$1 at sf1.isc.org>,
 linuxnewbie1234 <linuxnewbie1234 at nowhere.com> wrote:

> Suppose I have a company ONE for which I am serving the domain .one.com
> I know the A addresses of a computer like www.one.com
> however my company recently splitted and now there is an independent 
> branch, which is two.one.com  .
> 
> At TWO-ONE They have their computers (e.g. three.two.one.com), and their 
> NS which is ns.two.one.com . 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 three.one.com . TWO-ONE will be 
> informed of the split but not me.
> 
> Since I have the top level NS ns.one.com 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 X.one.com it first goes looking in my 
> zone file and then if this finds nothing, either
> -goes asking recursively to ns.two.one.com OR
> -tells the client to refer to ns.two.one.com
> ?

Delegate the subdomain two.one.com to their nameservers.

> 
> Note that I cannot simply put an NS entry specifying X.two.one.com NS 
> ns.two.one.com because if they split again forming "three" I wouldn't 
> catch that one. I really want a fallback on ns.two.one.com 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 
three.two.one.com -- 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 alum.mit.edu
Arlington, MA
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