D. J. Bernstein
Internet publication
djbdns
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 DNS clients and by some DNS caches.
For example,
dnscache assigns an IP address of 1.2.3.4
to the domain name 1.2.3.4.
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.