>>>It's not that important. I was just wondering if something was
>>>missing from the protocol. I have noticed that whenever my IP
>>>address changes, which is only when I change my MAC address, or
>>>when they move me to a different subnet, that I have reverse DNS
>>>for a while. Eventually, it disappears.
>>Did you leave out a word there? Did you mean to write "that I have reverse
>>DNS problems for a while"?
>Nope. I meant that it is there for a while, and then disappears.
>It's been gone for a long time.
>>On some systems, the system they use to put customer IP assignments into
>>DNS takes a little while to propagate. There's nothing you can do about
>>it, it's part of the ISP's DHCP/DNS design.
>I notice that today I do have reverse DNS for my home IP address.
>The address hasn't changed for about a year. I'll just put it down
>to quirks of Shaw's nameserver.
Any active IP address ought to return something in response to a
reverse DNS lookup, even if it is a generic placeholder which
essentially is just a string version of the IP address. If it
really returns nothing (NXDOMAIN), it can break (at least) ftp
and outbound email transfers. The ISP should be responsible for
this in the default, although some allow you to administer your
own reverse lookups, if you have a static IP and the technical
acumen to set up a nameserver and zone file to do so, through a
process called reverse CNAME delegation.
If rDNS is failing, it is likely that the ISP's nameservers have
a problem, and if it is consistently failing, it is even more likely
the ISP is blissfully unaware of the problem. (Obviously, it can
also be on your end, if you have requested and gotten a delegation.)
Gary, if you'd like to privately mail me your IP address, I will
take a look at it with "dig" and see if I can narrow down what is