The role of reverse zone files

[Stephane Bortzmeyer]

On Mon, Nov 08, 2004 at 03:45:38AM +0000,
 bob prohaska <bp at fib.eecs.berkeley.edu> wrote 
 a message of 36 lines which said:

> Forward zone files for each domain make obvious sense, but I'm a
> little hazy on the role of reverse domain files: Any nameserver with
> forward zone files can tease out reverse information; what's the
> need for reverse zone files?

Yes, your nameservers could find the answer (and that was the purpose
of the now deprecated IQUERY request). But how the rest of the world
would find them? The tree of domain names has no relationship with the
tree of IP addresses.

For a similar reason, you can declare yourself authoritative for
hotmail.com, it will not disturb Hotmail because nobody will ask your
nameservers about hotmail.com (except your small network, of course).
 
> There are only 5 addresses in the reverse file for all three
> domains; will one 5.161.64.in-arpa file suffice

It does not depend on the number of addresses. If they are all in
64.161.5.0/24, yes, one file will suffice.

But it is unlikely that you have the complete /24, so you will
probably have to use RFC 2317, which makes things more complicated,
unfortunately. Talk to your upstream provider, because they will have
to delegate to you.