DNS - PTR record (Pointer)

About

A PTR record is a DNS record with the pointer type (PTR type) .

It's used to permits or set up a reverse lookup where an ip address as input gives you its domain name.

Only the owner of the IP can set a reverse record, not the owner of the domain. Therefore if you want to set a PTR record:

  • for a server, you need to do it at your server provider
  • for your internet connection, you need to ask it to your telecom provider

Authentication

A PTR record is important because it's a part of request authentication on the Internet.

ie when a server got a request from an IP, it performs:

If they don't match, the request is classified as bad.

For instance:

Format

The PTR records are stored within the .arpa top-level domain.

Ipv4

142.175.106.72.in-addr.arpa. 86400 IN    PTR     name.apex.domain

where:

  • 142.175.106.72 is the IP
  • in-addr.arpa is the namespace (for Ipv4) where the records are stored. ie in the arpa domain

Ipv6

IPv6 PTR records are stored under the IPv6 address, reversed and converted into four-bit sections (as opposed to 8-bit sections, as in IPv4), plus “.ip6.arpa”.

Server provider

You Server provider should give you an interface to create it for a host

Example ovh on the cloud planel:

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