Reverse DNS lookup

Reverse DNS lookup (rDNS) is the process of determining the domain name associated with an IP address. This is the opposite of a normal DNS lookup, which converts domain names to IP addresses.

Reverse DNS uses PTR (pointer) records in the DNS system. These records are stored in special reverse DNS zones (in-addr.arpa for IPv4 and ip6.arpa for IPv6).

Common uses of reverse DNS include:

• Email server verification - many mail servers check reverse DNS to reduce spam
• Network troubleshooting and diagnostics
• Server identification and logging
• Security analysis and threat detection