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    • .arpa

    Infrastructure top-level domainDNSSEC

    Overview

    • .arpa is a top-level domain (TLD) in the Domain Name System used predominantly for management of Internet technical infrastructure.
    • The string originally came from the Advanced Research Projects Agency (ARPA); it was later redefined as the backronym "Address and Routing Parameter Area."
    • Operated operationally by the Internet Assigned Numbers Authority (IANA) with sponsorship/oversight by the Internet Architecture Board (IAB); technical management and allocation of subdomains are performed via IETF processes.

    History

    • Introduced in 1985 as the first formal domain in the nascent DNS and intended as a temporary transition namespace for ARPANET hosts.
    • Retained for infrastructure uses when it proved impractical to remove after the transition to categorized TLDs such as .com, .org, .edu, .gov and .mil.
    • In 2000 the IAB re-designated .arpa as the Address and Routing Parameter Area and recommended that new infrastructure delegations be placed in .arpa rather than .int.
    • The .arpa zone was signed with DNSSEC in March 2010.
    • The special-use name home.arpa was reserved in May 2018 for residential non-unique DNS names to avoid leakage and DNSSEC requirements associated with a public .home TLD.

    Usage and Audience

    • Primary purpose: operational Internet infrastructure and protocol-specific namespace allocation.
    • Key infrastructure uses include:
      • Reverse DNS lookups:
        • in-addr.arpa — IPv4 reverse mapping
        • ip6.arpa — IPv6 reverse mapping
      • Telephone-number mapping (ENUM): e164.arpa
      • Residential network special-use: home.arpa
      • Traffic sinking/blackholing for reverse lookup queries: as112.arpa
      • Service and resolver discovery: service.arpa, resolver.arpa
    • Typical users and audiences: IETF working groups, network operators, DNS operators, and other technical communities requiring delegated infrastructure namespaces.

    Registration Rules

    • There are no public domain registrations under .arpa; registrations are not possible in the usual commercial sense.
    • New subdomains are created through IETF work groups and the RFC process and are maintained by IANA; additions are infrequent and driven by standards/operational needs.
    • Dispute policy: none (zone is for infrastructure delegations).

    SEO and Brand Impact

    • .arpa is an infrastructure-only TLD and is not intended for branding or commercial domain registrations.
    • As an operational zone, .arpa was DNSSEC-signed in 2010 to provide cryptographic integrity for DNS data in the zone.

    Notable Cases or Examples

    • in-addr.arpa — IPv4 reverse DNS mapping (widely used for PTR records).
    • ip6.arpa — IPv6 reverse DNS mapping.
    • e164.arpa — ENUM mapping of E.164 telephone numbers to Internet URIs.
    • home.arpa — reserved special-use domain for residential non-unique names (RFC 8375).
    • as112.arpa — used by AS112 blackhole servers to sink certain reverse DNS traffic.
    • ipv4only.arpa — used for detecting DNS64/NAT64 environments.
    • ns.arpa, in-addr-servers.arpa, ip6-servers.arpa, uri.arpa and urn.arpa — additional infrastructure-related delegations maintained in the .arpa zone.

    Operator

    Internet Architecture Board (IAB)

    Whois

    % IANA WHOIS server
% for more information on IANA, visit http://www.iana.org
% This query returned 1 object

domain:       ARPA

organisation: Internet Architecture Board (IAB)
address:      c/o IETF Administration LLC
address:      1000 N. West St.
address:      Suite 1200
address:      Wilmington DE 19801
address:      United States of America (the)

contact:      administrative
name:         Internet Architecture Board (IAB)
organisation: Internet Architecture Board (IAB)
address:      c/o IETF Administration LLC
address:      1000 N. West St.
address:      Suite 1200
address:      Wilmington DE 19801
address:      United States of America (the)
phone:        +1 510 492 4080
fax-no:       +1 510 492 4001
e-mail:       iab@iab.org

contact:      technical
name:         Internet Assigned Numbers Authority (IANA)
organisation: Internet Corporation for Assigned Names and Numbers (ICANN)
address:      12025 Waterfront Drive
address:      Suite 300
address:      Los Angeles CA 90094
address:      United States of America (the)
phone:        +1 310 301 5800
fax-no:       +1 310 823-8649
e-mail:       tld-contact@iana.org

nserver:      A.NS.ARPA 198.41.0.4 2001:503:ba3e:0:0:0:2:30
nserver:      B.NS.ARPA 170.247.170.2 2801:1b8:10:0:0:0:0:b
nserver:      C.NS.ARPA 192.33.4.12 2001:500:2:0:0:0:0:c
nserver:      D.NS.ARPA 199.7.91.13 2001:500:2d:0:0:0:0:d
nserver:      E.NS.ARPA 192.203.230.10 2001:500:a8:0:0:0:0:e
nserver:      F.NS.ARPA 192.5.5.241 2001:500:2f:0:0:0:0:f
nserver:      G.NS.ARPA 192.112.36.4 2001:500:12:0:0:0:0:d0d
nserver:      H.NS.ARPA 198.97.190.53 2001:500:1:0:0:0:0:53
nserver:      I.NS.ARPA 192.36.148.17 2001:7fe:0:0:0:0:0:53
nserver:      K.NS.ARPA 193.0.14.129 2001:7fd:0:0:0:0:0:1
nserver:      L.NS.ARPA 199.7.83.42 2001:500:9f:0:0:0:0:42
nserver:      M.NS.ARPA 2001:dc3:0:0:0:0:0:35 202.12.27.33
ds-rdata:     42581 8 2 f28391c1ed4dc0f151edd251a3103dce0b9a5a251acf6e24073771d71f3c40f9

whois:        whois.iana.org

status:       ACTIVE
remarks:      Registration information:
remarks:      https://www.iana.org/domains/arpa

created:      1985-01-01
changed:      2023-11-27
source:       IANA