Getting familiar with rDNS

What does rDNS mean?

Reverse DNS, or simply for short rDNS, is a service normally included in your managed DNS plan. With it, you are able to perform reverse DNS lookups. For that purpose, it allows you to make a Reverse DNS zone and add inside it multiple PTR records. They serve you to prove that the IP addresses are associated with the domain name.

You are able to implement rDNS only with IPv4 addresses or IPv6 addresses or use both at the same time. With PTR records, you are able to provide proof that there is no some type of scam. That way, the servers of other businesses are capable of backtracking the IP address to the domain name and noticing a piece of actual evidence for that.

You are going to need a combination of A (IPv4) or AAAA (IPv6) records that link a domain name to IP addresses and PTR records that provide the opposite, linking IP addresses to a domain name.

So, let’s briefly put it this way:

Forward DNS: A domain name is pointing to an IP address where it is hosted. 

Reverse DNS: An IP address is pointing to a domain name to validate it belongs to it.

What’s rDNS for?

  • It is popular to use it as a security technique for verifying the proper match between an IP address and a domain name. However, if they do not match, there is a large possibility of a men-in-the-middle attack such as a phishing attack with malicious intent. A mismatch is going to show that someone has modified the data, and it is most likely unsafe.
  • rDNS is beneficial for business owners to guarantee that the emails they send are actually reaching their proper destination and they are not ending in the spam folder. In addition, it makes sure that the emails they receive are secure and not a bad threat.
  • It could help to get the name of Internet service providers (ISPs) correlated with particular IP addresses. 
  • Searching domain registry and registrars files, rDNS can also trace the domain of a machine attempting to break a firewall, spammers, or hackers. 
  • Owners of IP networks commonly need rDNS because it helps them to organize their network in a better way.

Master Reverse DNS Zone

For the purpose of using rDNS, you are going to have to make a Master Reverse DNS Zone. Note that IP addresses have to be written in reverse. The rDNS is able to operate with IPv4 addresses and IPv6 addresses. In the Master Reverse DNS Zone, you are able to add the PTR records. That is the only place where PTR records are capable of existing.

PTR record

The PTR record, the pointer record, is the DNS record that serves for the required mapping, which is an IP address to hostname. You are going to need an A or AAAA record for each PTR record you add.

You are going to need the PTR records and the Master Reverse DNS Zone when you want to verify the outgoing mail servers. There is going to be an examination of both the PTR records and the A records through the process. Therefore, it is critical to ensure that your DNS records are established correctly. In case they are improperly set, your email will end up in spam folders.

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