Glossary: Reverse DNS
Reverse DNS (rDNS) is the process of resolving an IP address to its associated hostname.
How Reverse DNS Works
Reverse DNS uses PTR (pointer) records stored in special domains. For IPv4, the IP is reversed and appended to in-addr.arpa. For IPv6, each hexadecimal digit is reversed and appended to ip6.arpa.
Uses of Reverse DNS
- Email validation: Many mail servers require valid PTR records
- Network diagnostics: Identifying devices by hostname
- Security logging: Making logs more readable
- Access control: Some services use reverse DNS for authentication
Setting Up Reverse DNS
Reverse DNS must be configured by whoever controls the IP address block - usually your ISP or hosting provider. The hostname in the PTR record should match a forward DNS record pointing back to the same IP.