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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?

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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. 1.2.3.4 can have a PTR record of xyz.domain.com and 1.2.3.5 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 255.255.255.0 for your particular case. –  Split71 Dec 28 '11 at 14:00
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migrated from stackoverflow.com Dec 28 '11 at 12:32

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1 Answer

up vote 1 down vote accepted

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.

http://www.crucialp.com/resources/tutorials/web-hosting/how-reverse-dns-works-rdns.php

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