What is Reverse DNS and How it Works

November 15, 2021 / Domain and DNS

This article will teach you what reverse DNS is and how it works.

Reverse DNS (rDNS) is the process of resolving an IP address to a domain name, which is the inverse of a forward DNS query.

What is Reverse DNS?

A DNS lookup of a domain name from an IP address is known as reverse DNS. rDNS resolves an IP address from a domain name, but standard DNS performs the inverse, thus the term reverse.

PTR records are used for reverse DNS lookups. Address and Routing Parameter Area (in-addr.arpa) domains are used to configure pointer records. A reverse DNS lookup fails if no PTR record is configured.

What is the Objective of Reverse DNS Server?

Reverse DNS is very beneficial for people who maintain an outgoing mail server. Aside from mail servers, there are various more reasons to use rDNS:

  • Spam email filtering : Most email servers use rDNS to prevent spam by rejecting messages from IP addresses that do not have rDNS. However, rDNS is mostly used as an additional layer of protection since it is unreliable due to the fact that some legal mail servers do not have correctly configured rDNS records.
  • Analytics : Instead of publishing logs of IP addresses, reverse DNS assists in providing human-readable data in analytics.
  • Keeping track of website visitors: IP addresses of website visitors are saved in visit logs and can help you understand your website’s audience. Tracking website visitors is useful for generating B2B leads.
  • A pleasant network experience : Most corporate management systems, r-commands, SMTP servers, and network backup systems are not affected by reverse DNS. rDNS is also a prerequisite for operating several Internet protocols.
  • Security : A reverse IP lookup may be used to locate the A records for an IP address, linking a domain name to the actual IP address of the device hosting that domain. The findings aid in determining the virtual hosts serviced by a web server as well as identifying server flaws.

What is the Process of Reverse DNS Lookup?

Reverse DNS works by querying DNS servers for a pointer record (PTR). A PTR record links an IPv4 or IPv6 address to the host’s canonical name. A reverse lookup cannot be resolved if there is no PTR record on the server.

PTR records are used to hold reverse DNS entries, which have their IP address reversed and the suffix.in-addr.arpa attached to each record. PTR, for example, records the IP address as, which points back to the designated host name.

It is essential to put up a good reverse DNS record (PTR), particularly when operating an SMTP/mail server.

The difference between DNS and rDNS lookups is depicted in the picture below.

DNS lookup
rDNS lookup

PTR records in IPv6 hold rDNS entries in the.ip6.arpa domain,
Instead of.in-addr.arpa

You may reach a domain name with a valid rDNS by typing its IP address into your browser.

What is Reverse DNS and how can you do it?

Reverse DNS lookup may be done in a variety of ways:

  • Use the command prompt in Windows: Utilize the nslookup command to do a manual rDNS lookup on Windows.
  • Use the command prompt in Linux: The dig command with the -x parameter enables manual rDNS lookups. Alternatively, the host command may be used.
  • Use lookup tools for rDNS records: rDNS lookup is available via a number of tools.

Command for Reverse DNS Lookup

This section, Manual reverse DNS lookup on Windows or Linux is covered.

In Windows, you may do a reverse DNS lookup.

In Windows, the reverse DNS lookup command is:

nslookup [ip_address]

For example :

windows reverse DNS lookup

The domain name for the specified IP address is returned in the output.

The command produces an error if the website does not have rDNS set up. Consider the following scenario:



In Linux, you may do a reverse DNS lookup.

In Linux, there are two methods to search up rDNS:

  1. The dig command is
    To execute a manual reverse DNS search in Linux, use the dig command. The syntax is as follows:
    dig -x [ip_address]

    For example :
    LINUX reverse DNS lookup
    The domain name for the supplied IP address is shown in the output.
  2. The command “host”
    In Linux, you can also use the following command to do a reverse DNS lookup:
    host [ip_address]


You now understand what reverse DNS is and how to use it in Windows, Linux, and internet tools. if you continue to have problems with the protocol outlined above, please contact the eukhost team for constructive assistance 24 hours a day, 7 days a week.

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