Reverse Lookup Zone Question

[Christian Smith]

In article <dro95k$2k21$1 at sf1.isc.org>,
 Tom Naves <tman at sdf.lonestar.org> wrote:

> I have two mail exchangers for two domains:
> 
> mydomain.com
> mail.mydomain.com 192.168.40.134
> mail2.mydomain.com 192.168.40.131
> 
> 
> mydomain.net
> mail.mydomain.net 192.168.40.131
> mail2.mydomain.net 192.168.40.134
> 
> My question: can I make a reverse lookup zone 40.168.192.in-addr.arpa that 
> will resolve all the above names to the ip address?
> 
> Thanks,
> 
> Tom

I don't think you asked the question you meant to ask. Your forward 
zones already handle resolving "all the above names to the ip address". 
What you wanted to ask was:

Can I make a reverse lookup zone 40.168.192.in-addr.arpa that will 
resolve those IP addresses to all of the names?

Yes, you can create multiple PTR records for a single IP address, so in 
the 40.168.192.in-addr.arpa zone you can have

131.40.168.192.in-addr.arpa.    PTR    mail.mydomain.net.
131.40.168.192.in-addr.arpa.    PTR    mail2.mydomain.com.

134.40.168.192.in-addr.arpa.    PTR    mail2.mydomain.net.
134.40.168.192.in-addr.arpa.    PTR    mail.mydomain.com.

But, this is not necessary. You only need a single PTR record which 
points to a single name which in turn has an A record that points back 
to the IP address.

Adding multiple PTR records for an IP address just makes it harder to 
manage when you do need to make a change.


-- 
Christian Smith
Dynamic Network Services, Inc.