Reverse DNS

Reverse DNS lookup (rDNS)

Με τον όρο reverse DNS lookup εννούμε την διαδικασία κατά την οποία θέλουμε να βρούμε το όνομα / hostname ή host που αντιστοιχεί σε μία IP address (διεύθυνση IP) ή αλλιώς host address. Αυτό γίνεται για παράδειγμα κάθε φορά που δοκιμάζουμε κάποιο traceroute.

A reverse lookup is often referred to as reverse resolving, or more specifically reverse DNS lookup, and is accomplished using a "reverse IN-ADDR entry" in the form of a PTR record.

Reverse DNS requirement

RFC 1912 Section 2.1 states "Every Internet-reachable host should have a name" and "Make sure your PTR and A records match". RFC 1033 Section "INSTRUCTIONS" states the following (note especially the last sentence):

   Adding a host.

      To add a new host to your zone files:

         Edit the appropriate zone file for the domain the host is in.

         Add an entry for each address of the host.

         Optionally add CNAME, HINFO, WKS, and MX records.

         Add the reverse IN-ADDR entry for each host address in the
         appropriate zone files for each network the host i[s] on.