Environment
- Primary DNS
Working with PTR Records
A PTR record is used to perform a reverse DNS lookup. A domain pointer defines a domain name associated with an IP address. A forward DNS lookup resolves a domain name (e.g., www.example.com) points to an IP Address (e.g., 192.0.2.100).
A PTR record involved in a reverse lookup for an IPv4 address uses the special domain in-addr.arpa. A PTR record for IP address 8.8.8.8 would be defined as follows:
8.8.8.8.in-addr.arpa. 21599 IN PTR google-public-dns-a.google.com.
PTRs record used for resolving reverse lookups for an IPv6 address uses the special domain ip6.arpa.
Tools commonly use PTR records, like traceroute and ping, to resolve the hostname of an IP address. Anti-spam software can perform reverse lookups against DNS denylists to perform transaction-time spam blocking by associating an email agent's IP address with those lists.