How to set up Reverse DNS

As the name implies, Reverse DNS is the inverse of normal (forward) DNS. DNS (Domain Name Service) translates a human readable URL or domain name into an IP address for the computer to read. Reverse DNS is useful when you have an IP address and need to find the domain name.

A Reverse DNS query will offer a Reverse Pointer or PTR record. Although Reverse DNS seems straightforward, it can be tricky to set up. Despite performing the reverse function of standard DNS, the two are completely different and separate lookups.

How to set up Reverse DNS

Step 1: Create a Reverse DNS zone.

It is very important that you create the reverse DNS zone on the authoritative DNS nameserver for the main IP address of your server. If the Reverse response is not already provided by your nameserver, you can contact your hosting provider to set up a PTR record.

If you control the authoritative nameserver, you can go ahead with creating a reverse DNS zone. The format for the zone hostname must be very specific, starting with a fragment of your IP address written in reverse followed by .in-addr.arpa. For example:

1. If your IP address is 192.168.0.100, drop the last set of numbers to make 192.168.0
2. Reverse the IP fragment to make 0.168.192
3. Add .in-addr.arpa. to get the complete reverse zone domain of 0.168.192.in-addr.arpa.

Step 2: Create the PTR record.

You’ve created your zone file; now you can create the PTR record. First, add a new PTR record and enter the final octet of the IP address that you’re setting up the reverse record for as the name of the record. This will be the set of numbers that you removed in Step 1.

In our example, the name will be 100. Then, enter the domain name you want the IP address to resolve to for the Canonical Hostname. For example, mailserver.example.com. Lastly, save your zone file and allow time for the change to take effect.

Step 3: Validate your reverse DNS record.

You can validate the new reverse DNS record by running the DIG Web Interface Tool. If the setup is a success, you should get a lookup answer that looks similar to this:

100.0.168.192.in-addr.arpa. 6230   IN   PTR   mailserver.example.com

Speak to HOSTAFRICA for DNS advice

Having Reverse DNS set up shows that you care about your internet reputation. Reverse DNS will start becoming even more important with the implementation of IPV6. At HOSTAFRICA, we can assign your Reverse DNS on request and ensure that both your Reverse and Forward DNS match.

Contact us today for assistance with Reverse DNS setup.