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Overview

Reverse DNS uses pointer records (PTR) to convert IP addresses to domain names. Forward DNS uses A records to convert domain names to IP addresses.

Configure reverse DNS


System requirements

PTR records require authoritative DNS nameservers before they can function properly.

To find the authoritative DNS nameservers of your server's main IP address, trace the Start Of Authority (SOA). To do this, run the appropriate command:

IPv4

dig +nssearch 0.168.192.in-addr.arpa

Note:

In this example, 0.168.192.in-addr.arpa represents your server's main IP address.

IPv6

dig +nssearch 8.4.7.2.3.b.1.8.5.e.5.2.8.e.d.f.ip6.arpa

Note:

In this example, 8.4.7.2.3.b.1.8.5.e.5.2.8.e.d.f.ip6.arpa represents your server's main IP address.

Important:

  • Changes to your server's DNS nameservers do not take effect if your server's DNS nameservers are not authoritative for your IP address. Many hosting providers do not delegate authority for PTR records to their customers.
  • Contact your upstream provider to either delegate authority to your nameservers or set up PTR records for your nameservers.

 

 

 


 

Add the reverse DNS zone.

Navigate to WHM's Add a DNS Zone interface (WHM >> Home >> DNS Functions >> Add a DNS Zone) and enter the following information:

  • Your server's IP address in the Ip text box.
  • The reverse DNS zone's name in the Domain text box.

    • For information about how to name a reverse DNS zone, click the link below that corresponds to your IP address version.

       IPv4 reverse DNS zone

      To create a reverse DNS zone name for an IPv4 address, perform the following steps:

      1. Drop the last octet from the IP address.
      2. Reverse the order of the octets that remain.
      3. Append in-addr.arpa to the end of the octets.

      A complete reverse DNS zone name for an IPv4 address will resemble the following example:

      128/24.0.168.192.in-addr.arpa

      Note:

      If your hosting provider delegates you a byte boundary that is greater than 25, separate the network range and byte boundary with a dash (), rather than a forward slash (/). For example:

      128-25.0.168.192.in-addr.arpa

      For more information, read the RFC 2317 documentation.

       IPv6 reverse DNS zone

      To properly format the Domain text box in the interface with IPv6, perform the following steps:

      1. Identify the nibbles to specify in the zone file. Nibbles appear at the end of the IPv6 address, for example:

        0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.d.2.0.0.0.0.0.0.2.6.2

        Important:

        You must configure IPv6 reverse DNS zones in nibble format. For information about how to convert an IPv6 address to nibbles, visit the Reverse DNS v6 website.

      2. Remove the nibbles to specify in the zone file.
      3. Reverse the order of the nibbles that remain in the IPv6 address.
      4. Append ip6.arpa to the end of the zone file's name.

      A complete reverse DNS zone entry for an IPv6 address will resemble the following example:

      1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.

The Domain Information section of WHM's Add DNS Zone interface.

 


 

Edit the reverse DNS zone file.

After you create your zone file, create each PTR record in WHM's Edit DNS Zone interface (WHM >> Home >> DNS Functions >> Edit DNS Zone).

Note:

Your zone file already contains an NS entry for each of your server's authoritative nameservers.

  • Enter the octets or nibbles in an available text box under the Add New Entries Below this Line heading.
  • Select PTR in the appropriate menu. The Hostname text box will appear.
  • Enter the hostname that corresponds to the last octet or nibble in the IP address.


Create a PTR record in the Edit DNS Zone interface.

 


 

Test your records.

After your domain's DNS information propagates, confirm that you properly configured reverse DNS.

Click your IP version's link below for instructions about how to test your reverse DNS zone configuration.

 IPv4

To confirm that you properly configured reverse DNS, run the following command:

host 192.168.0.1

If you correctly configured reverse DNS, the output will resemble the following example:

1.0.168.192.in-addr.arpa domain name pointer www.example.com.
 IPv6

To confirm that you correctly configured reverse DNS, run the following command:

host 7.d.6.e.0.5.e.f.f.f.0.9.5.2.2.0.0.0.4.1.0.0.0.0.8.b.d.0.1.0.0.2

If you correctly configured reverse DNS, the output will resemble the following example:

7.d.6.e.0.5.e.f.f.f.0.9.5.2.2.0.0.0.4.1.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa domain name pointer www.example.com

 


Additional documentation