.arpa Reserved special-use name

What is .arpa?

The .arpa top-level domain is the “Address and Routing Parameter Area” domain and is designated to be used exclusively for Internet-infrastructure purposes. IANA administers the domain in cooperation with the Internet technical community through the guidance of the Internet Architecture Board.

For further information, see Management Guidelines & Operational Requirements for the Address and Routing Parameter Area Domain ("arpa") (RFC 3172).

Under the hood, the root zone points to 12 name servers for .arpa, every one of them reachable over IPv6. The delegation is DNSSEC-signed, so resolvers can verify that answers for .arpa haven't been tampered with on the way. Registration data is published over WHOIS (the WHOIS server is whois.iana.org).