AS401

AS401 is a legacy autonomous system number registered under ARIN to Air Force Systems Networking, a U.S. Department of Defense / U.S. Air Force entity administered by the Defense Information Systems Agency (DISA). The key structural fact for triage is that AS401 has no discrete RDAP autnum object of its own: an ARIN RDAP query for autnum 401 resolves to the shared block record AFCONC-BLOCK1-AS (handle AS379), which spans AS379–AS508. AS401 therefore inherits its registrant, contacts, address, top-level registration event, and "active" registry status from that block rather than carrying an operator-official identity of its own. Unlike its live sibling AS399, AS401 is presently dormant in routing: RIPEstat reports it as not announced (announced:false), with an empty announced-prefixes array over the 2026-06-18 to 2026-07-02 window and zero RIS peers seeing it (0/323 IPv4, 0/321 IPv6). It was, however, historically routed — RIPEstat routing-status records a first-seen origination of 214.4.27.0/24 on 2005-08-20 and a last-seen of 38.156.73.0/24 on 2023-12-22 — consistent with a within-block DoD number that has since been withdrawn from the global table, plausibly through federal network consolidation. The registrant org (ARIN OrgId 7ESG) is validated and holds dozens of ASN and IPv4 allocations across Air Force installations. No PeeringDB profile exists for AS401, and no notable public abuse signal was found as of 2026-07-02. CAIDA AS rank and customer cone could not be retrieved (the CAIDA fetch timed out) and are left as sourced Unknowns rather than fabricated. A bgp.he.net listing showing Turkish-operator "peers" (AS9121, AS202561) is treated as stale/uncorroborated and is not adopted, since RIPEstat reports zero observed neighbours and the identity is a dormant DoD block.

Operator

Air Force Systems Networking (U.S. Air Force / DoD; ARIN OrgId 7ESG; registrant of the AFCONC-BLOCK1-AS block AS379–AS508) [Confirmed] — ARIN RDAP autnum/401 (resolves to block handle AS379), rdap.arin.net/registry/entity/7ESG

Country / RIR

US, ARIN [Confirmed] — RIPEstat abuse-contact-finder (authoritative_rir: arin), ARIN RDAP autnum/401

Allocated

1989-08-04 (ARIN registry date on the AFCONC-BLOCK1-AS block record's TOP-LEVEL events; NOT an IEEE date — IEEE publishes no ASN registration dates); last changed 2008-06-06 [Confirmed] — ARIN RDAP autnum/401 top-level events[] (registration / last changed)

Org status

active / validated per ARIN RDAP (status inherited from the parent block record handle AS379; 7ESG entity status = validated, last changed 2025-03-13); no operator-official source confirms AS401-specific operational detail beyond routing observation [Confirmed for RDAP status; Unknown for operator-official detail] — ARIN RDAP autnum/401, rdap.arin.net/registry/entity/7ESG

Contacts

registration/abuse/technical via DISA-Columbus — disa.columbus.ns.mbx.arin-registrations@mail.mil; +1-844-347-2457 ext. 2 (POC handle REGIS10-ARIN, 300 North James Road, Whitehall, OH 43213, US). Registrant org (7ESG): 501 East Moore Dr., Bldg 884, Rm 1100, Gunter Annex, Maxwell AFB, AL 36114, US

[Confirmed] — ARIN RDAP autnum/401

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-02 — not in Spamhaus SBL/DROP/ASN-DROP, AbuseIPDB aggregations, or NANOG archives for AS401; consistent with a currently unrouted, non-transit U.S. government block

Network & routing

Network type

U.S. government / military network (DoD, U.S. Air Force), administered by DISA (DISA-Columbus); not a commercial ISP, hosting, or content network [Confirmed] — ARIN RDAP autnum/401, rdap.arin.net/registry/entity/7ESG

Size

dormant — 0 announced IPv4 prefixes / 0 IPv4 addresses and 0 IPv6 prefixes as of the query window; not currently in the global routing table [Confirmed] — RIPEstat as-overview (announced:false), announced-prefixes (empty), routing-status (announced_space v4/v6 = 0)

Routing/peering

NOT announced — 0 RIS peers seeing it (0/323 v4, 0/321 v6), 0 observed neighbours; historically routed (first-seen 214.4.27.0/24 on 2005-08-20; last-seen 38.156.73.0/24 on 2023-12-22). No per-ASN peering policy published; no PeeringDB profile (peeringdb.com/asn/401), and AS401 is absent from the same-named org profile org/20118 (stale, last updated 2018, lists a different ASN set) [Confirmed for not-announced / no-PeeringDB; Confirmed for historical routing] — RIPEstat routing-status, bgp.tools/as/401, peeringdb.com/org/20118

RPKI

not assessed this pass — RIPEstat rpki-validation requires a --prefix argument that was not supplied, and with 0 current announcements there is no route to validate; posture Unknown, not fabricated [Unknown] — RIPEstat rpki-validation (skipped: no --prefix)

AS rank / customer cone

Unknown — CAIDA fetch errored (operation aborted, timeout); not independently re-queried this pass [Unknown] — CAIDA (timeout in source data)

Notable usage

none documented on any operator-official source; no public page names AS401 by number. It is a within-block number of the AFCONC-BLOCK1-AS allocation (AS379–AS508), sibling to other DoD/Air Force ASNs already enriched in this pipeline (e.g. AS399) [Unknown for operator-official; Confirmed for block membership] — ARIN RDAP autnum/401

Uncorroborated caution

bgp.he.net lists AS9121 and AS202561 (Turkish telecom operators) as "peers" of AS401 — flagged as likely stale/cached and NOT adopted: uncorroborated by RIPEstat (0 observed neighbours) and implausible for a dormant DoD/Air Force block [Unknown] — bgp.he.net/AS401

Analyst note

Encountered as a dormant within-block DoD/Air Force ASN whose RDAP resolves to the shared AFCONC-BLOCK1-AS record (handle AS379); allocated_date (1989-08-04) and last_updated (2008-06-06) were read strictly from the autnum TOP-LEVEL events[], not the entity-nested decoy dates (7ESG org 2008-06-05/2025-03-13; REGIS10-ARIN POC 2009-06-24/2026-02-12).