I'm trying to create a PTR records for a domain, but I'm a bit confused.

I've looked at PTR records on another server with Plesk installed and the records contained the IP for server and then /24 afterwards. What is the /24 and should I use /24 (or something else)?

How do I found that out?

  • Interesting, but off-topic. Nominated for webmasters (it sounds appropriate). – pst Dec 15 '11 at 0:30
  • Actually, it's best suited for serverfault. – jweyrich Dec 15 '11 at 5:28
  • You dont create PTR records for a domain, you create them for a subnet. can have a PTR record of xyz.domain.com and can have a PTR record of bleh.blah.com. It's not tied up to domains. – pauska Dec 28 '11 at 12:39
  • the /24 is the bits for the subnet mask. Meaning for your particular case. – Split71 Dec 28 '11 at 14:00

PTR records are a special case. Whoever supplies your IP addresses (usually your host/ISP), must do one of the following:

  • Set up your reverse DNS entries on their DNS servers.
  • Delegate authority" for your reverse DNS entries to your DNS servers.

This has to do with the unique nature in which reverse DNS is resolved.

I would contact your host to resolve this and disable/remove the PTR records on the Plesk system.

Another note about reverse DNS is that it is a 1:1 mapping. You should not have multiple PTR records mapping an IP to a domain. In contrast, you can have multiple A records mapping different domains to the same IP.

Here is a good resource on PTRs.


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