In contrast to a forward DNS query, reverse DNS (rDNS) resolves an IP address back to a domain name. You will discover What Is Reverse DNS and How It Works? in this post.

What Is Reverse DNS?

A DNS lookup of a domain name from an IP address is known as reverse DNS. DNS resolves an IP address from a domain name instead of the other way around like a typical DNS request, hence the term reverse.

For reverse DNS lookups, a PTR record is utilized. Within Address and Routing Parameter Area (in-addr. arpa) domains, pointer records are configured. A reverse DNS lookup fails if no PTR record has been put up.

What Purposes Does Reverse DNS Lookup Serve?

What Is Reverse DNS and How Does It Works? Running an outgoing mail server makes Reverse DNS especially important. In addition to mail servers, there are a number of benefits to rDNS use:

1: Removing spam from emails.

Most email servers refuse messages from IP addresses without rDNS in order to block spam. However, since some trustworthy mail servers don’t have correctly configured DNS records, rDNS is mainly utilized as an additional layer of security.

2: Analytics.

Instead of simply listing logs of IP addresses, reverse DNS helps give data that can be analyzed by humans.

3: Tracking the usage of a website.

The IP addresses of website visitors are recorded in the visit logs and can be used to determine who is visiting your website. The production of B2B leads can benefit from tracking website visitors.

4: Effortless network interaction.

The majority of enterprise management systems, r-commands, SMTP servers, and network backup solutions won’t cause you any trouble if you use reverse DNS. One of the prerequisites for using several Internet protocols is rDNS.

5: Security.

An IP address can be located using a reverse IP lookup, which links a domain name to the actual IP address of the computer hosting the domain. The findings aid in identifying server vulnerabilities and the virtual hosts that a web server serves.

How Does Reverse DNS Lookup Work?

Searching DNS servers for a pointer record is how reverse DNS operates (PTR). An IPv4 or IPv6 address is mapped to the host’s canonical name via a PTR record. It cannot resolve a reverse lookup if the server has no PTR record.

PTR records keep track of reverse DNS entries, with each record’s IP address reversed and the extension. in-addr. arpa added. PTR, for instance, records the IP address 198.15.93.98 as 98.93.15. 198. in-addr. arpa, which refers to the specified hostname.

What Is Reverse DNS and How Does It Work? A good reverse DNS record (PTR) configuration is advised, especially when hosting an SMTP/mail server.

The difference between a DNS and a DNS lookup is shown in the following image:

1. PTR records for IPv6 instead use the.ip6.arpa domain to hold DNS entries.
2. You can reach a domain name if its rDNS is active by typing its IP address into your browser.

How to Do a Reverse DNS?

Reverse DNS lookup can be done in several different ways:

1. Use Windows’ command-line interface. Utilize the nslookup command in Windows to do rDNS lookup manually.
2. Make use of the Linux terminal. You can manually look up rDNS information by using the dig command with the -x parameter. Use the host command instead.
3. Use tools for rDNS lookups. A number of tools provide DNS lookup.

Command for Reverse DNS Lookup

What Is Reverse DNS and How Does It Work? The manual reverse DNS lookup on Windows or Linux is covered in this section.

1: Windows Reverse DNS Lookup

In Windows, the reverse DNS lookup command is:

• search for "IP address"

For instance:

The domain name associated with the given IP address is returned in the output.

The command gives an error if rDNS has not been configured for the website. For instance:

2: Linux Reverse DNS Lookup

What Is Reverse DNS and How Does It Work? In Linux, there are two methods for rDNS lookup:

1: Using the dig command

If you want to manually look up a reverse DNS server, use Linux’s dig command. As for the syntax:

• [ip address] dig -x

For instance:

The domain name associated with the entered IP address is shown in the output.

2: The command host

Linux also has the following command for reverse DNS lookup:

• The IP address of the host

For example:

The domain name for the supplied IP address is displayed in the output.

Backward DNS Tools

What Is Reverse DNS and How Does It Work? The tools that can be used for reverse DNS lookup are listed in this section.

1: Online Resources

Reverse DNS lookups are possible using a few addresses using online tools. Some might even offer an API for business use cases:

1. https://dns.google.com/
2. https://mxtoolbox.com/ReverseLookup.aspx
3. https://www.whatismyip.com/reverse-dns-lookup/
4. https://hackertarget.com/reverse-dns-lookup/
5. https://whatismyipaddress.com/ip-hostname

2: Business-Grade Tools

You may automate and carry out rDNS lookups on several IP addresses using other enterprise-grade tools. These are a few of the tools:

1. https://reverseip.domaintools.com/ – enables you to locate every domain hosted on a specific IP address. For Personal and Enterprise Members, lookups are free for IPs with up to 2,000 hosted domains.
2. https://reverse-ip.whoisxmlapi.com/ – a RESTful API appropriate for automated programs or scripts. Uses API calls to provide a list of all domains connected to a given IP address, and it produces results in JSON and XML formats.
3. https://viewdns.info/ – Several tools, such as rDNS lookup and an API, are available to web developers so they can include the tools in their websites. There are XML and JSON output formats available.
4. https://toolbox.googleapps.com/apps/dig/ – a network utility that produces outcomes comparable to those of the Linux dig command.
5. https://dnsinspect.com/ – A free web tool that checks your domain’s servers for common DNS and mail errors and generates a report explaining on how to fix them.

Conclusion

Now that you understand What Is Reverse DNS and How Does It Work? you can check it up on Windows, Linux, and online using various tools. You are welcome to test the tools, however, keep in mind that some websites may not have rDNS configured, in which case the tools produce an error.