Reverse DNS Lookup

A reverse DNS lookup is a DNS query for a domain or hostname against a given IP address. It is the opposite of a forward DNS lookup, in which a DNS query can get the IP address against a domain or hostname.

The Internet Engineering Task Force (IETF) standard suggests that every domain on the internet should perform the reverse DNA lookup. But that is not a hard-coded rule. Therefore, reverse DNA lookup is not universally adopted.

In reverse DNS lookup, the DNS query is performed to DNS servers for getting the PTR (Pointer) record. If the server does not have the PTR record, then the reverse lookup cannot be performed.

PTR records store the IPv4 addresses with their segments reversed, and they append ".in-addr.arpa" to that. However, in IPv6, PTR records are kept within the ".ip6.arpa" domain instead of ".in-addr.arpa."

Email servers commonly use reverse DNS entries to check that the email comes from the valid server before bringing it into their network. Many email servers will reject messages from any server that does not support reverse DNS lookups or from a server that has a bad reputation.

Many Internet services, network tools, and logging software also employ reverse dns lookups to provide users with human-readable domains in their log data instead of many numeric IP addresses.

• For that, open the tool: Hostname to IP Resolver.
• Enter an IP address. Here is a sample, enter IP address 8.8.8.8 and click on the "Check Now" button.
• The tool performs the reverse DNS lookup and provides you the domain or hostname associated with the IP address. Here the hostname against IP address 8.8.8.8 is dns.google.