RFC 1912, Sec 2.1:
Which is 'Informational', not standards track...
" Make sure your PTR and A records match. For every IP address, there should be a matching PTR record in the in-addr.arpa domain. If a host is multi-homed, (more than one IP address) make sure that all IP addresses have a corresponding PTR record (not just the first one).
I have yet to hear a convincing argument why this RFC should be ignored. I have seen many problems when this is ignored.
The major problem here is software packages that can't deal with the possibility of setups like this: www.mycorp.com CNAME round-robin.server.mycorp.com round-robin.server.mycorp.com A 198.168.1,1 A 198.168.2.1 A 198.168.3.1 Yes, major software vendors are still managing to get this Totally Wrong. And when somebody at the VP level says something WILL be deployed in time for another non-negotiable deadline (for instance, 25K students returning to campus), you end up with some ugly ad-crockery with PTRs ;) Yes, we'll fix the PTRs. Soon as we get a patch from the vendor. 'Nuff said. ;) -- Valdis Kletnieks Operating Systems Analyst Virginia Tech