Configuring Reverse DNS for BIND in WHM

The information contained here is about configuring reverse DNS for BIND in WHM. Pointer records (PTR) are used by Reverse DNS for converting IP addresses to domain names. Forward DNS uses A records for converting domain names to IP addresses.

Certain steps need to be carried out for determining the authoritative nameservers of your server. You can set PTR records on your CPanel & WHM server, if it is authoritative. Usually, most of the users of cPanel & WHM don’t have the authority to edit their PTR records directly. Reverse DNS management in a client interface is offered by some providers. When the term “providers” is being used here, web hosting service providers are being referred to. These companies provide the service of web hosting. Users of web hosting services have many options to choose from, for hosting purposes, such as “Shared Windows Hosting”, “Dedicated Linux Hosting”, “VPS Hosting”, etc.

Important Facts

Any change to the DNS nameservers of your server do not take effect unless the DNS nameservers of your server are authoritative for your IP address. Many of the providers of hosting do not delegate authority for PTR records to their clients.

You should contact your provider to either delegate authority to your nameservers or set up your nameservers’ PTR records.

How to Configure Reverse DNS?

1. System Requirements

Authoritative DNS nameservers are required by PTR records prior to functioning properly.

You need to trace the SOA (State of Authority) in order to find the authoritative DNS nameservers of the main IP address of your server. For this purpose an appropriate command needs to be run. An example is mentioned below.

dig +nssearch 0.168.192.in-addr.arpa

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

A point to note is that the Add a DNS Zone interface of WHM doesn’t support IPv6 currently. 

WHM >> Home >> DNS Functions >> Add a DNS Zone

Points to Remember

Changes to the DNS nameservers of your server do not take effect unless the DNS nameservers of your server are authoritative for your IP address. Many of the providers of hosting do not delegate authority for PTR records to their clients.

You need to contact your upstream provider for either delegating authority to your nameservers or set up PTR records for your nameservers.

2. Add the Reverse DNS Zone

Navigate to the Add a DNS Zone interface of WHM.

WHM >> Home >> DNS Functions >> Add a DNS Zone. Subsequently enter the information mentioned below.

• Enter the IP address of your server in the text box, IPv4 Address. Enter the name of the reverse DNS zone in the Domain text box.

• You need to carry out the following steps for creating a reverse DNS zone name for an IPv4 address:

• Drop the last octet from the IP address.

• Reverse the order of the remaining octets.

• Append in-addr.arpa to the end of the octets.

• An IPv4 address’ complete reverse DNS zone name will resemble the example mentioned below. 128/24.0.168.192.in-addr.arpa

It needs to be mentioned here that if your hosting provider delegates a byte boundary to you that is greater than 25, the network range and the byte boundary should be separated with a dash (-) rather than a forward slash (/).

Edit the Reverse DNS Zone File

• After you have created your zone file, you need to create each PTR record in the Edit DNS Zone interface of WHM.

WHM >> Home >> DNS Functions >> Edit DNS Zone

 It needs to be mentioned here that your zone file already has an NS entry for each of your server’s authoritative nameservers.

• You need to enter the octets in the available text box. This text box is present under the Add New Entries Below this Line heading.

• PTR needs to be selected in the appropriate menu. The Hostname text box appears.

• The hostname that corresponds to the last octet in the IP address needs to be entered.

Test Your Records

After the DNS information of your domain has propagated, confirm that reverse DNS has been properly configured by you.

In order to confirm that you have properly configured reverse DNS, you need to run the below-mentioned command.

host 192.168.0.1

If the reverse DNS has been configured correctly by you, the output will resemble the example mentioned below. 1.0.168.192.in-addr.arpa domain name pointer www.example.com.

Now you have successfully configured Reverse DNS for BIND in WHM.

Source: https://www.htshosting.org/knowledge-base/technology/175/configuring-reverse-dns-for-bind-in-whm