What is the purpose of Reverse DNS?
Reverse DNS – What is it?
Reverse DNS, also known as rDNS, is a DNS lookup that maps an IP address to its domain name. It is absolutely the opposite of Forward DNS lookup, where the domain name links to the IP address where it is hosted.
In the majority of cases, rDNS is an additional service provided by a DNS hosting provider. Once you implement such a service, you should create a Master Reverse zone and add PTR records to it. That way, you are able to provide evidence that your IP address and your domain name have a proper match.
Thanks to the created PTR record, you actually confirm that the IP address is associated with the domain name. As a result, you are minimizing the chance and avoiding fraud. Additionally, you can implement Reverse DNS both with IPv4 address and A record and with IPv6 address and AAAA record.
Master Reverse Zone
As we mentioned, if you want to use Reverse DNS properly, you are going to need a Master Reverse Zone. Once you create it for your domain name, you should know that each IP address should be in reverse order. In addition, rDNS operates perfectly both with IPv4 addresses and IPv6 addresses. Later on, if you need to, you are able to create additional PTR records. It is important to note that the only place where PTR records are able to exist is exactly the Master Reverse Zone.
PTR record
The PTR record is also called pointer record, and it serves to link the IP address (IPv4 or IPv6) to a hostname. You should know that you should have a corresponding A or AAAA record for every PTR record you create. For instance, if you want to verify the outgoing mail servers, you should create PTR records in the Master Reverse Zone. There is going to be a lookup of both the PTR records and the A records during the process. For that reason, it is crucial to make sure you configure your DNS records correctly without any mistakes. Otherwise, there is a great chance for your emails to land directly into the spam folder of your recipients.
What is Reverse DNS used for?
Reverse DNS is highly beneficial, and it could be used for the following purposes:
Security: It is commonly involved in verifying the accurate match of the IP address and the domain name. In case they do not correspond to each other, there is a potential for a man-in-the-middle attack (phishing attack) that has a malicious purpose. When a mismatch appears, it is a sure sign that a cybercriminal changed the data, and there is a security issue.
Email: Businesses benefit from rDNS a lot. It ensures that all of their emails are delivered to their customers successfully, and there is no chance for them to be considered spam.
Tracing: When searching domain registry and registrars files, Reverse DNS could be helpful for finding the domain of a device that attempts to crack a firewall, spammers, or hackers.
Better organization: Typically, owners of extensive IP networks implement Reverse DNS for improving and organizing them.