Check reverse DNS records and forward-confirmation status for any IP address or domain name.
A reverse DNS lookup, sometimes also known as a reverse IP lookup is a type of DNS lookup request which does the opposite of the much more common forward lookup. A forward lookup will convert a domain name like www.example.com into an IP address like 192.0.2.1, while a reverse lookup will convert an IP address back into a domain name.
Reverse DNS records are not required to be configured for DNS to function correctly, and forward and reverse DNS records do not even have to agree with each other - but if they do, then this is referred to as a forward-confirmed reverse DNS.
Reverse DNS records are not stored with other DNS records for the domain name they are for, but instead are stored on the special .arpa domain name. The DNS record type used for reverse DNS is known as a PTR record, short for a Pointer record.
PTR records take on a special format depending on if they are for IPv4 A records or IPv6 AAAA records. A records live under the .in-addr.arpa subdomain while AAAA records are within .ip6.arpa.
The DNS record for the IPv4 address 192.0.2.1 is 2.1.0.192.in-addr.arpa.
The reverse DNS record for the IPv6 address 2002:7f00:1:: is 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.0.0.0.0.0.f.7.2.0.0.2.ip6.arpa.
You can use the reverse DNS record generator to learn more about the special format required, as well as easily create them with the online tool.
Reverse DNS records for an IP address is quite often not required, especially given most DNS resolution happens as a forward lookup for converting easy for humans to remember domain names into IP addresses for computers, but there are some advantages to consider taking advantage of.
Email deliverability - Email servers commonly use reverse lookups to verify that the emails are coming from servers which are designated to be allowed to send email on behalf of the domain in question. Email servers will often reject messages from servers which do not have reverse DNS records as they are more likely to be used for sending spam.
Ease of identity - Many system administrators find it convenient to capture IP addresses as well as reverse DNS records in their log files in order to easily identify trends in traffic by looking at domain names rather than IP addresses.
There are many ways to do a reverse DNS lookup, but due to the special format required for reverse DNS records it is often much easier to use an online tool which automatically converts the request into the correct format.
The easiest way to do a reverse DNS lookup is by using the tool on this page. Simply enter the IP address you wish to resolve and press the lookup button.
The tool will also automatically perform additional forward lookups on any alternative results which allows you to quickly and easily get insight into all available matching records.
For added convenience, you can also enter a domain name and a reverse DNS lookup will be performed on the resulting IP addresses.
Windows includes the DNS lookup tool nslookup, this tool will allow you to perform many types of lookup requests including PTR records for reverse DNS entries.
Fortunately nslookup makes the process of reverse DNS lookups easy and will automatically perform the PTR record conversion into the correct .arpa domain for you.
To find the reverse DNS entry for the IP address 192.0.2.1 using your systems built in DNS resolver:
nslookup 192.0.2.1
To find the reverse DNS entry for the IP address 192.0.2.1 using the specified DNS resolver 1.1.1.1:
nslookup 192.0.2.1 1.1.1.1
Linux operating systems like Ubuntu, CentOS & Redhat as well as Apple Mac OS include a few different tools available for performing reverse DNS lookups. The most commonly used is dig as it can provide a lot of technical details used for diagnosing issues, while the host command is simple and provides easy to read output without having to remember extra command line options.
To find the reverse DNS entry for the IP address 192.0.2.1 using your systems built in DNS resolver:
host 192.0.2.1
To find the reverse DNS entry for the IP address 192.0.2.1 using the specified DNS resolver 1.1.1.1:
host 192.0.2.1 1.1.1.1
note: the above commands recognise that the request is for an IP address and assumes a reverse DNS lookup so automatically implies the -t ptr parameter. The equivalent full form command would be:
host -t ptr 192.0.2.1
To find the reverse DNS entry for the IP address 192.0.2.1 using your systems built in DNS resolver:
dig -x 192.0.2.1
To find the reverse DNS entry for the IP address 192.0.2.1 using the specified DNS resolver 1.1.1.1:
dig -x 192.0.2.1 @1.1.1.1
