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Does PTR pointing to domain is forbidden? If so - which RFC states that. The same with A record pointing at the domain. As I see, usually, people are trying to avoid such configurations. But I would like to be precise here. Is it forbidden or not. Thanks.

Example: 3600 IN A

and 7200 IN PTR

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up vote 2 down vote accepted

Your example is completely valid. There is no problem with that at all - it is a very very common configuration.

The main thing you should not do on a domain, but can do on a hostname, is setting a CNAME. This because on the domain name, there will always be NS records and those can never be combined with a CNAME.

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I have found it very useful to use A records for physical hosts and CNAME records for services (such as websites, ftp sites, VPN sites, etc.) In that way I can easily move a service from one host to another and it is visible which host a particular service or site is located on. – wolfgangsz Aug 25 '10 at 12:35
I do the same, most of the time :) – Erik Aug 25 '10 at 13:07
Ok. Thanks for the answer. In this topic I would like to be perfectly precise. @wolfgangsz yes - it is very good habit. Moreover if you have a environement with huge amount of devices, it is good to create additional level of abstraction within domain name scope and have subdomains like: (all web services), (all security services) etc. – plluksie Aug 27 '10 at 9:46

A PTR record is just an additional information. Some sites / e-mailsystems require correct ptr setups.

  • An A record points from a domainname/hostname to an ip.
  • An PRT record points from an ip to an domainname/hostname

It's a good option to have both, but you need at least an A record.

RFC's for DNS:

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