AS331

AS331 is a legacy autonomous system number registered under ARIN to the United States Department of Defense (DoD) and operated by the DoD Network Information Center (DoD NIC), a function carried out by the Defense Information Systems Agency (DISA) from its Columbus, Ohio facility. The ASN sits inside the contiguous DoD block DNIC-ASBLK-00306-00371 (AS306–AS371), a single ARIN registration that covers all 66 ASNs in that range and supplies the authoritative first-party registry facts for AS331. RIPEstat's as-overview confirms the holder string "DNIC-ASBLK-00306-00371 - United States Department of Defense (DoD)" and places the resource in the IANA 16-bit AS registry block 1-1876 assigned by ARIN. Operationally AS331 is near-dormant: as of the 2026-06-28 query its as-overview shows announced=false and routing-status reports zero currently announced v4/v6 prefixes, though it was intermittently active in the two weeks prior, originating five IPv4 prefixes in DoD-reserved 55.0.0.0/8 space (two /16s plus two /24s) and one IPv6 prefix (2608:14a:2300::/40), last seen 2026-06-26. Its first observed origination dates to 2009-12-10 (55.70.0.0/16). CAIDA AS Rank was unreachable (HTTP 502) so AS rank, customer cone, and upstream/peer identities are Unknown. The abuse contact is the DISA-Columbus DoD NIC hostmaster, and no notable public abuse signal was found — a single WAYSCloud-flagged IP (55.70.73.206, 2025-12-05, rated MINIMAL) is the only data point across Spamhaus, CleanTalk, AbuseIPDB, NANOG archives, and BGP incident records.

Operator

DoD Network Information Center (DoD NIC) — operated by DISA for the United States Department of Defense; ARIN org handle USDDD [Confirmed] — ARIN RDAP autnum 306, ipinfo.io/AS331, ip2location.com/as331

Country / RIR

US, ARIN [Confirmed] — RIPEstat abuse-contact-finder (authoritative_rir: arin)

Allocated

1989-06-30 (ARIN RDAP autnum top-level registration event for block AS306–AS371 covering AS331; RIR first-party fact, NOT an IEEE date); last changed 2025-09-12 [Confirmed] — ARIN RDAP autnum 306 top-level events

Org status

active U.S. federal government agency (DoD / DISA); ARIN record status active [Confirmed] — ARIN RDAP autnum 306, ipinfo.io/AS331

Contacts

abuse/hostmaster disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil; +1-844-347-2457 ext2; United States Department of Defense, 3990 E. Broad Street, Columbus, OH 43218 [Confirmed for abuse via RIPEstat; Likely for postal via RDAP] — RIPEstat abuse-contact-finder, ARIN RDAP autnum 306

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-06-28 — single WAYSCloud-flagged IP 55.70.73.206 (1 report, 2025-12-05, risk MINIMAL); no Spamhaus DROP/SBL/ASN-DROP listing, no CleanTalk stats, no AbuseIPDB cluster, no NANOG incident threads, no BGP hijack/leak attributed to AS331 (the AS8003 DoD-pilot controversy is unrelated) [Confirmed for verdict; Likely for individual feeds] — ip.wayscloud.services/asn-intelligence/331, spamhaus.org, kentik.com/blog/the-mystery-of-as8003

Network & routing

Network type

U.S. government military/defense network; ARIN registrant category Government; classified as a stub AS (single-homed, provides no transit) [Confirmed] — ipinfo.io/AS331, ip2location.com/as331

Size

near-dormant — 0 IPv4 prefixes / 0 IPv6 prefixes currently announced (routing-status, announced=false at 2026-06-28T08:00:00Z). When active in the prior 2 weeks: 5 IPv4 prefixes (55.70.190.0/24, 55.19.2.0/24, 55.19.0.0/16, 55.70.0.0/16, 55.65.0.0/16) and 1 IPv6 prefix (2608:14a:2300::/40)

[Confirmed] — RIPEstat announced-prefixes / routing-status

Routing/peering

not currently announced; when active, v4 visibility 324/326 RIS peers and v6 visibility 324/324; observed_neighbours=2 but upstream/peer ASN identities not enumerated in primary data [Confirmed for visibility/counts; Unknown for peer identities] — RIPEstat routing-status

Peering policy

Unknown — no PeeringDB entry for AS331, no public peering policy published; consistent with a stub military network [Unknown] — peeringdb.com, ipinfo.io/AS331

RPKI

Unknown — RIPEstat rpki-validation requires a --prefix and was skipped; not assessable from the data collected [Unknown] — RIPEstat (rpki-validation skipped)

AS rank / customer cone

Unknown — CAIDA AS Rank returned HTTP 502 at query time [Unknown] — asrank.caida.org/asns?asn=331

Routing history

first seen 55.70.0.0/16 origin AS331 on 2009-12-10; last seen 2608:14a:2300::/40 on 2026-06-26T16:00:00 [Confirmed] — RIPEstat routing-status

Notable usage

one of 66 ASNs in the DoD NIC-managed block AS306–AS371; supports U.S. Department of Defense communications infrastructure in DoD-reserved 55.0.0.0/8 IPv4 space. (Note: the G root DNS server g.root-servers.net, a related DoD NIC function, is announced from AS5927, not AS331) [Confirmed for block membership; Likely for G-Root operator linkage] — ipinfo.io/AS331, root-servers.org, disa.mil/G-Root

Related ASNs

AS306 (block parent, also DoD), AS749 (DoD NIC), and other DoD NIC ASNs in the AS306–AS371 range; AS8003/GRSCORP used for some separate DoD prefix announcements [Confirmed for AS306/AS749; Likely for broader list] — asrank.caida.org/asns?asn=331, community.nanog.org

Analyst note

AS331 is one entry in the DoD NIC block DNIC-ASBLK-00306-00371; the block-level RDAP autnum record (autnum 306) is authoritative for allocated_date (1989-06-30). Entity-nested events (MIL-HSTMST-ARIN 1993-05-26, REGIS10-ARIN 2009-06-24) are contact/org-level and were NOT used for allocated_date. Near-dormant with intermittent recent originations; clean abuse posture.