# ptrcalc Displays reverse zone for a given IPv6 or IPv4 Address. ```bash ~$ ptrcalc 42.43.123.43/29 IP Address: 42.43.123.43/29 Reverse pointer: 43.123.43.42.in-addr.arpa Zone: 123.43.42.in-addr.arpa Host: 43 RFC2317: Reverse pointer: 43.40/29.123.43.42.in-addr.arpa Zone: 123.43.42.in-addr.arpa Host: 43 ``` Supports RFC2317 and JSON output.