What is reverse DNS?
Reverse DNS resolves an IP address back to a domain name by looking up PTR (pointer) records. While standard DNS maps names like example.com to IP addresses, reverse DNS does the opposite: it maps an IP like 93.184.216.34 back to a hostname.
PTR records are stored in a special in-addr.arpa zone for IPv4 (and ip6.arpa for IPv6). They are configured by the entity that controls the IP address block, usually the ISP or hosting provider.
Common use cases
- Email authentication: Verify that your mail server has a valid PTR record, which is required by many receiving mail servers.
- Network troubleshooting: Identify which hostname is associated with an IP you see in logs or traceroutes.
- Security analysis: Determine the owner or purpose of an IP address found in access logs or firewall rules.
- Server verification: Confirm that hosting provider PTR records match your expected server hostname.