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.
Mail servers use Reverse DNS information to help validate a message’s source domain. System administrators use Reverse DNS information to help identify inbound connections trying to get past a firewall or other security.
If your cPanel & WHM server is authoritative, you can use your DNS server to update your server’s PTR records. However, most cPanel & WHM users do not have the authority edit their PTR record directly. Instead, some hosting providers offer reverse DNS management in a client interface. For more information, contact your hosting provider.
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 allow their customers to modify their nameserver PTR records. Contact your hosting provider to delegate authority to your nameservers or set up your nameserver PTR records.
If you are updating PTR records for mail purposes, it is only necessary to update the records for IP addresses that your sites use to send mail.
PowerDNS is the default nameserver and is fully compatible with serving Reverse DNS records.
Configure reverse DNS
In the following examples:
example.com represents your domain.
192.168.0.1 represents your main IP address.
0.168.192.in-addr.arpa represents your server’s main IP address, in PTR record format.
If your hosting provider delegates you a byte boundary that is greater than 25, separate the network range and byte boundary with a dash (–) character. Do not use a forward slash (/) character. For example, 128-24.0.168.192.in-addr.arpa represents a server’s main IP address with a byte boundary that is greater than 25 in PTR record format. For more information, read the RFC 2317 documentation.
Note:
This interface does not currently support IPv6.
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) record. To do this, run the following command:
dig +nssearch 0.168.192.in-addr.arpa
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:
.1Enter your server’s IP address in the IPv4 Address text box.
.2Enter the reverse DNS zone’s name in the Domain text box.
.3Create a reverse DNS zone name for an IPv4 address. To do this, perform the following steps:
.4Drop the last octet from the IP address.
.5Reverse the order of the remaining octets.
.6Append .in-addr.arpa to the end of the octets.
A reverse DNS zone name for an IPv4 address will resemble 0.168.192.in-addr.arpa.
Edit the reverse DNS zone file
After creating your zone file, create the reverse DNS zone file’s PTR record in WHM’s DNS Zone Manager interface (WHM » Home » DNS Functions » DNS Zone Manager).
Note:
Your zone file already contains a Nameserver (NS) record for each of your server’s authoritative nameservers.
To add the DNS zone’s PTR record, perform the following steps:
.1In WHM’s DNS Zone Manager interface, click Manage next to the domain you want to modify. The system will direct you to an interface that displays the domain’s current list of zone records.
.2Click Add Record. The system will create a new record entry row in the table.
.3Select PTR from the Type menu.
.4Enter the name that you created with WHM’s Add a DNS Zone interface (WHM » Home » DNS Functions » Add a DNS Zone) into the Name text box.
.5Enter the remainder of the reverse DNS zone address in the Record text box. In this example that would be either 1 or 128-24 depending on the server’s byte boundary.
.6Click Add Record.
Test your records
After your domain’s DNS information propagates, confirm that you properly configured reverse DNS. 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.