Mike Walter wrote:
We have a customer that has AT&T and they reassigned the IP space to our name servers to allow us to do reverse DNS for them.
We had a similar situation. AT&T states that they will only handle rDNS using domains that they control. They will happily CNAME the IPs appropriately or reassign the IP space, depending on block size and request. The issue we ran into was that we couldn't get them to *unassign* a CNAME for an IP block so that it would fail immediately, and so servers (web,ftp, etc) which requested rDNS for the connection information would time out connections waiting for the non-existent nameservers. We weren't really interested in handling rDNS for the IP given that it wasn't handling mail, web, or have any A records pointing to it. It is the easiest way to get it done, though. Jack Bates