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.