AS421

AS421 is a legacy autonomous system number administered under ARIN as part of a single flat block record — AFCONC-BLOCK1-AS, handle AS379, spanning AS379 through AS508 — registered to "Air Force Systems Networking," an organization of the U.S. Department of Defense / U.S. Air Force at Maxwell AFB, Alabama, with administrative and abuse contacts handled by DISA-Columbus (the Defense Information Systems Agency) in Whitehall, Ohio. There is no per-ASN delegation record for AS421: ARIN's RDAP autnum endpoint returns the block-level object (startAutnum 379, endAutnum 508) even though every link and value in the JSON is stamped "autnum/421," a known ARIN pattern for legacy flat-allocated DoD ranges. The key triage point is that AS421 is effectively dormant today. Every routing source consulted — RIPEstat, CAIDA AS Rank, bgp.he.net, bgp.tools — agrees it announces zero IPv4 and zero IPv6 prefixes, has zero visible BGP peers, zero upstreams, zero customers, and no IXP memberships. Its CAIDA AS rank of 79,459 sits near the bottom of the global ranking, and its customer cone is a singleton (the ASN itself, 0 prefixes, 0 addresses). The only historical routing on record is a single brief announcement of 192.107.166.0/24, first seen 2002-02-05 and last seen 2002-05-06, not observed since. RPKI posture cannot be assessed because there are no active originations and therefore no ROAs. No notable public abuse signal was found as of 2026-07-02 across IPinfo, Hurricane Electric, NANOG archives, and BGP-hijack reporting, consistent with a clean, dormant government-held block.

Operator

Air Force Systems Networking (U.S. DoD / U.S. Air Force; ARIN registrant handle 7ESG, Maxwell AFB, AL; admin/abuse via DISA-Columbus, Whitehall, OH) [Confirmed] — ARIN RDAP (rdap.arin.net/registry/autnum/421), ipinfo.io/AS421

Country / RIR

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

Allocated

1989-08-04 (ARIN registry date for the containing block AS379–AS508, the only allocation record ARIN publishes for AS421 — RIR registry fact, not an IEEE date); last changed 2008-06-06 [Confirmed] — ARIN RDAP autnum top-level events; corroborated by bgp.tools/as/421

Org status

registered/active at the block level per ARIN; operationally dormant/unrouted per CAIDA; no evidence of revocation or reassignment [Likely] — ARIN RDAP, asrank.caida.org/asns/421

Contacts

abuse disa.columbus.ns.mbx.arin-registrations@mail.mil; phone +1-844-347-2457 ext2; registrant 501 East Moore Dr., Bldg 884, Rm 1100, Gunther Annex, Maxwell AFB, AL 36114; admin/abuse POC DISA-Columbus, 300 North James Road, Whitehall, OH 43213 [Confirmed] — ARIN RDAP, RIPEstat abuse-contact-finder

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-02 — convergent negative results across IPinfo, Hurricane Electric bgp.he.net, NANOG archives, and BGP-hijack reporting (Kentik/Catchpoint/Cloudflare Radar). Spamhaus ASN-DROP was NOT directly queried (tooling policy), so that specific listing is Unknown rather than confirmed clear

Network & routing

Network type

U.S. government / military network block (Department of Defense, Air Force); not a commercial ISP or enterprise network; AS421 is legacy/inactive [Confirmed] — ARIN RDAP, ipinfo.io/AS421

Size

dormant — 0 IPv4 prefixes / 0 IPv4 addresses and 0 IPv6 prefixes; customer cone = 1 ASN (itself), 0 prefixes, 0 addresses [Confirmed] — RIPEstat routing-status / CAIDA AS Rank / bgp.he.net / bgp.tools (2026-07)

Routing/peering

NOT announced — 0 RIS peers seeing it (0/324 v4, 0/320 v6); CAIDA degree total 0 (customer 0, peer 0, provider 0); no upstreams or peers visible in any source [Confirmed]. No PeeringDB record exists (HTTP 404); no public peering policy found [Confirmed] — peeringdb.com/asn/421

RPKI

not assessable — AS421 announces no prefixes, so there are no ROAs to validate; RIPEstat rpki-validation requires a prefix parameter and none is announced [Confirmed] — stat.ripe.net rpki-validation

Notable usage

dormant DoD legacy block. Only historical routing on record is a single brief announcement of 192.107.166.0/24 (first seen 2002-02-05, last seen 2002-05-06); not observed since [Confirmed] — RIPEstat routing-status

Related ASNs

AS421 is one of 130 consecutive ASNs (AS379–AS508) in the single AFCONC-BLOCK1-AS flat block record (handle AS379) [Confirmed] — ARIN RDAP

Analyst note

Encountered as a dormant legacy DoD ASN with no per-ASN RDAP record — ARIN returns the flat AS379–AS508 block object. Block-level registration date (1989-08-04) is the correct/only allocation date for AS421 and is recorded per RIR-registry-fact policy; entity-level last-changed dates (registrant 7ESG 2025-03-13, abuse POC REGIS10-ARIN 2026-02-12) are record-touch events, not the autnum registration date, and are excluded from allocated_date/last_changed.