rDNS – How to use it?

The rDNS (Reverse DNS) process is just one part of the Domain Name System’s overall operation. The goal is to link a domain name to an IP address. In our article today, we will take a detailed look at its purpose and why you need to implement it.

What is a PTR record?

First, to better understand what rDNS is, we will explain an essential part. So, one of the DNS record types that use the IP address to determine whether or not it has a reverse zone is the PTR record (or Pointer record). It keeps track of the user’s reverse IP address and ensures that messages sent to them don’t end up in their spam folder.
The structure of the PTR record is as follow:

  • TYPE: PTR – the type of the record
  • HOST: 169.71.46.216 – the reverse IP address of the domain (it could be IPv4 or IPv6)
  • POINTS TO: exampledomain.net – the domain name
  • TTL: 1h – the limit of its validity or time-to-live

What exactly is rDNS?

As we all know, DNS is the method through which we use a domain name to find its IP address. The Reverse Domain Name System, or rDNS, obtains information about a domain name by using the IP address. As a result, this procedure is the polar opposite of traditional DNS resolution.
DNS hosting providers are usually the ones who provide the rDNS service. In essence, after you obtain it, you will be able to create a reverse Master zone. Then, you can validate the correct match between IP addresses and their domain names by adding PTR records to this zone.

Why do you need rDNS?

There are different reasons why it is necessary to have rDNS. However, we will look at the two most important, which are:
1. To avoid spam. Unwanted messages can be anything from spam to life-threatening threats. So, they could be seeking advertising or propagating malware, phishing, and other malicious software. By verifying IP addresses, rDNS can significantly minimize spam. If they’re legitimate, rDNS will discover it!
2. To obtain easily readable logs. Logging systems only keep track of IP addresses, the long strings of numbers you’re familiar with. With rDNS, the numbers could be transformed into domain names that are easier to understand in logs.

What is the way to check your Reverse DNS?

You can test your Reverse DNS by looking at the IP addresses and seeing if they point to the hostname. It is the same instruction for Linux, macOS, Windows, and other operating systems. All you have to do is use the Nslookup command:

nslookup 216.46.71.169

Change the IP address 216.46.71.169 in this example with the one you wish to check. In this situation, it’s an IPv4 address, but that doesn’t imply you can’t use an IPv6 address instead.

Conclusion

Online security is really important and not granted. Reverse DNS is a reliable verification mechanism that can help you improve your safety. rDNS assures the trustworthiness of services and proves the legitimate relationship between IP addresses and a domain.

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