reverse lookup via "type forward" - possible? realistic? feasible?

[Barry Margolin]

In article <c3a4k3$1c76$1 at sf1.isc.org>, didds2 at excite.com (Ian Diddams) 
wrote:

> But...  how do I resolve reverse lookups?  e.g. if fred.wxyz.co.uk has
> ip
> 121.122.123.124, how do I use a similar concept (ie type forward) to
> resolve that?
> 
> Presumably something along the lines of 
> 
> zone "123.122.121" {   [or should that just be "121.122.123" ?]
>   type forward;
>   forwarders {
>    a.b.c.d;
>    e.f.g.h;
>   };
>  };

The zone name should be "123.122.121.in-addr.arpa".

> 
> But IF that's true...  and wxyz.co.uk actually has dozens of subnets,
> then presumably I would need a "type forward" section for every
> subnet?

Unless the server handles reverse DNS for the entire 121.122.x.x address 
range, in which case you could have a forwarders statement for the 
corresponding reverse zone "122.121.in-addr.arpa".

> And if THAT's true, if a new subnet is introduced naturally the
> named.conf would need to be updated to reflect it?

Right.

> Finally, presumably the whole thing could be covered by a forwarder
> statement within the options section (and the type forward section
> above removed I guess!)...  what effect would that have on the
> external resolution (if any) given that the users for reasons best
> known to themselves require THIS dns box to resolve external addresses
> and NOT the forwarders.  (hope that last bit made sense!).

If you put a forwarders statement in the options section, it will be 
used for any zones that the server isn't authoritative for or doesn't 
have specific forwarding zones.  So all external lookups will be relayed 
through those forwarders, instead of this box doing them itself.  It 
doesn't sound like this meets your requirements.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
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