DNS on Windows Server 2003, 3rd Edition

The Loopback Address

Those of you familiar with the BIND name server may be wondering if we forgot about the loopback address. If we were setting up a BIND name server, it would need one additional zone datafile to cover the loopback network: the special address that hosts use to direct traffic to themselves. This network is (almost) always 127.0.0.0, and the host number is (almost) always 127.0.0.1. Therefore, the name of this file would be 0.0.127.in-addr.arpa.dns, and it would look like the other in-addr.arpa.dns files.

The following would be the contents of the 0.0.127.in-addr.arpa.dns file:

@                IN      SOA terminator.movie.edu.   administrator.movie.edu.   (
                        1           ; serial number
                        3600        ; refresh
                        600         ; retry
                        86400       ; expire
                        3600      ) ; minimum TTL

;
;  Zone NS records
;

@                       NS terminator.movie.edu.

;
;  Zone records
;

1                       PTR localhost.

Why do name servers need this file? Think about it for a second. No one was given responsibility for network 127.0.0.0, yet systems use it for a loopback address. Since no one has direct responsibility, everyone who uses it is responsible for it individually. If you omit this file on a name server, it will still operate. However, a lookup of 127.0.0.1 might fail: the name server will send the query to a root name server that might not be configured to map 127.0.0.1 to a name.

With the Microsoft DNS Server, you don’t have to worry about creating this file and making your name server authoritative for the in-addr.arpa zone corresponding to network 127.0.0.0. The server ...