D. J. Bernstein

Internet publication

DNScache

Special DNS names

Names not controlled by the roots

The localhost and 1.0.0.127.in-addr.arpa domains are handled internally by DNS caches. localhost has the address 127.0.0.1; 1.0.0.127.in-addr.arpa has a pointer to localhost.

Numeric top-level domains are handled internally by stub resolvers and by some caches.

Other names embedded in software

in-addr.arpa is used to look up host names by address.

Human-oriented names

RFC 2606 reserves test for DNS implementation testing. It also reserves example and invalid and example.com and example.net and example.org for made-up examples.