AS366

AS366 is a legacy autonomous system number registered under ARIN to the United States Department of Defense (DoD), organization handle USDDD. It is not a standalone allocation but one number inside the DNIC-ASBLK-00306-00371 block (AS306 through AS371), a contiguous range of DoD-numbered ASes administered by the Defense Information Systems Agency (DISA) DoD Network Information Center (DNIC) in Columbus, Ohio. The ARIN RDAP autnum top-level registration event for this block is dated 1989-06-30, which is the allocated date for AS366; the record was last changed on 2025-09-12. Unlike the dormant legacy ASNs common in this range, AS366 is actively announced: RIPEstat and CAIDA agree it originates roughly 17 IPv4 prefixes (about 65,536 addresses, all inside 55.82.0.0/16, part of the DoD's 55.0.0.0/8 space) plus a small IPv6 footprint. CAIDA ranks it a stub/leaf AS — customer cone of one (itself), a single upstream provider, no peers, and no IXP membership — consistent with a segregated military network rather than a commercial transit operator. No notable public abuse or threat signal was found as of 2026-07-01 across NANOG archives, general web search, and BGP/threat-intel aggregators, consistent with a DoD-administered block that is not a typical commercial-abuse-feed target. AS366 is distinct from AS5927 (the DoD-operated G-root DNS ASN); the two should not be conflated.

Operator

United States Department of Defense (DoD); ARIN org handle USDDD; block DNIC-ASBLK-00306-00371 administered by DISA DoD Network Information Center (DNIC), Columbus, OH [Confirmed] — ARIN RDAP autnum/366, ipinfo.io/AS366

Country / RIR

US, ARIN [Confirmed] — ARIN RDAP autnum/366 (port43 whois.arin.net, ARIN block)

Allocated

1989-06-30 (ARIN RDAP autnum TOP-LEVEL registration event for the DNIC-ASBLK-00306-00371 block containing AS366 — first-party RIR registry fact, NOT an IEEE date); last changed 2025-09-12

[Confirmed] — ARIN RDAP autnum top-level events (decoy entity/POC/org dates 1993-05-26, 2009-06-24, 2007-01-12 correctly excluded)

Org status

active (per ARIN RDAP autnum status field) [Confirmed] — ARIN RDAP autnum/366

Contacts

abuse/hostmaster disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil, +1-844-347-2457 ext2 (MIL-HSTMST-ARIN, "Network DoD"); registrant 3990 E. Broad Street, Columbus, OH 43218; POCs list DISA-Columbus, 300 North James Road, Whitehall, OH 43213 [Confirmed] — ARIN RDAP autnum/366

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-01 — searched NANOG archives, general web, and BGP/threat-intel aggregators (bgp.he.net, CAIDA AS Rank, Spamhaus); DoD-operated block, not a typical commercial-abuse-feed target. Absence of evidence is not evidence of absence — DoD incident handling is not publicly indexed

Network & routing

Network type

government / military network (U.S. DoD); third-party classifier tags ASN type "Government," not commercial hosting/ISP [Confirmed] — ipinfo.io/AS366

Size

actively announced — ~17 IPv4 prefixes / ~65,536 IPv4 addresses (all within 55.82.0.0/16) plus 2 IPv6 prefixes (2001:480:280::/48, 2608:10a:3600::/40); CAIDA customer cone = 1 ASN (itself), 16 prefixes, 6,656 addresses [Confirmed] — RIPEstat routing-status, CAIDA AS Rank (2026-07)

Routing/peering

stub/leaf AS — CAIDA asnDegree total 1 (provider 1, customer 0, peer 0); RIPEstat observed neighbours 2; no IXP membership; cliqueMember=true (stable, long-announced). Named upstream/peer ASNs not surfaced by RDAP/RIPEstat/CAIDA; aggregator data shows association with DoD ASes AS306 and AS668

[Likely] — RIPEstat, CAIDA AS Rank, ipinfo.io/AS366

RPKI

Unknown — RIPEstat rpki-validation requires a per-prefix query and was not run in this pull; no ROA data captured [Unknown]

Notable usage

DoD netblock 55.82.0.0/16 (part of the broader DoD 55.0.0.0/8 allocation); first announced 2008-08-05, currently active. Distinct from AS5927 (DoD-operated G-root DNS ASN) — do not conflate [Likely] — ipinfo.io/AS366, root-servers.org

Related ASNs

block DNIC-ASBLK-00306-00371 spans AS306–AS371 (all DoD); aggregator data shows AS366 associated with AS306 and AS668 [Confirmed for block range; Likely for AS306/AS668 association]

Analyst note

A DoD-numbered ASN inside a DISA-administered megablock. WHOIS/RDAP resolves to the U.S. Department of Defense; the block-level contacts and single-upstream stub topology are block/DoD-wide, not AS366-specific. No dedicated operator website exists for AS366 itself — disa.mil was unreachable during research (root ECONNREFUSED, /About 404, /g-root redirected to an unrelated third-party page), so operator-first-party web content could not be fetched; all non-RDAP claims are aggregator-derived and tagged accordingly. Clean, active, segregated military ASN.