Reverse DNS for IPv4 and IPv6

Reverse DNS allows the mapping of a domain name from an IP address. This is achieved by the use of pseudo-domain names under in-addr.arpa (IPv4) and ip6.arpa (IPv6). For all IP address blocks that IANA (the Internet Assigned Numbers Authority) allocates to APNIC, it also delegates corresponding reverse DNS zones within the centrally administered “in-addr.arpa” and “ip6.arpa” domains.