Page "Domain Name System" Paragraph 55

When performing a reverse lookup, the DNS client converts the address into these formats, and then queries the name for a PTR record following the delegation chain as for any DNS query.

For example, assume the IPv4 address < tt > 208. 80. 152. 2 </ tt > is assigned to Wikimedia.

It is represented as a DNS name in reverse order like this: < tt > 2. 152. 80. 208. in-addr. arpa </ tt >.

When the DNS resolver gets a PTR ( reverse-lookup ) request, it begins by querying the root servers ( which point to The American Registry For Internet Numbers ' ( ARIN's ) servers for the < tt > 208. in-addr. arpa </ tt > zone ).

On ARIN's servers, < tt > 152. 80. 208. in-addr. arpa </ tt > is assigned to Wikimedia, so the resolver sends another query to the Wikimedia nameserver for < tt > 2. 152. 80. 208. in-addr. arpa </ tt >, which results in an authoritative response.