reverse dns for multiple domains on same subnet

[Nick Trenary]

I have two domains on my subnet, call them domain1.com and domain2.com on
192.168.10.0. How is reverse DNS configured? There can be only one
10.168.192.in-addr.arpa zone file, right? If so, how is it configured for
multiple domains if both domains point to the same IP address?

Thanks,
Nick Trenary

[Kevin Darcy]

Post by Nick Trenary
I have two domains on my subnet, call them domain1.com and domain2.com on
192.168.10.0. How is reverse DNS configured? There can be only one
10.168.192.in-addr.arpa zone file, right? If so, how is it configured for
multiple domains if both domains point to the same IP address?

First ask yourself why you care about reverse records in the first
place. Is it because some silly app wants to "authenticate" a client by
doing a reverse lookup on its source address, followed by a forward
lookup of whatever it got from the reverse lookup -- the so-called
"double lookup" -- to verify that it gets the IP address with which it
started? If that's the case, then it only matters that the reverse
lookup returns *one* of the (possibly many) names which happen to
resolve to the relevant IP address. So just pick one forward name for
each address and be done with it. Or use some heuristic, e.g. in case of
multiple references, the alphabetically-highest name wins.

If you have some other reverse-DNS requirement(s) beyond "source-address
authentication by double lookup", then you need to define those more
clearly, to see if CNAMEs or some other technique will satisfy it/them.

- Kevin

[Barry Margolin]

Post by Nick Trenary
I have two domains on my subnet, call them domain1.com and domain2.com on
192.168.10.0. How is reverse DNS configured? There can be only one
10.168.192.in-addr.arpa zone file, right? If so, how is it configured for
multiple domains if both domains point to the same IP address?

Pick one and put it in the PTR record.