AS531

AS531 (DNIC-AS-00531) is a legacy, DNIC-prefixed autonomous system number allocated by ARIN on 1989-09-29 to Headquarters, USAISC — the U.S. Army Information Systems Command — a Department of Defense entity whose registrant record still lists Fort Huachuca, Arizona as its address of record and DISA-Columbus (Whitehall, Ohio) as its technical/abuse/administrative point of contact, per current ARIN RDAP data. USAISC itself was inactivated as a formal command in 1996, with its functions folded into successor Army network organizations, but the RDAP registrant name has never been updated to reflect that reorganization — a common pattern for legacy military DNIC-era allocations that predate ARIN's own founding. The autnum's RDAP status remains "active," meaning the registry record has not been revoked, yet current routing data tells a different story: RIPEstat and CAIDA both show zero announced IPv4 and IPv6 prefixes, zero visible peers or upstreams, and a singleton customer cone, with CAIDA ranking it 79,459th globally. This is not, however, a never-routed record — RIPEstat's routing-status history shows AS531 intermittently announcing prefixes from 2010-08-27 through as recently as 2023-07-28, making it a dormant-but-previously-active DoD ASN rather than a purely inert registry entry. No public abuse, hijack, or NANOG-discussion signal was found for AS531 in any consulted source, consistent with a low-profile, internally used military network with no public-facing operator website.

Operator

Headquarters, USAISC (U.S. Army Information Systems Command) — DoD/Army legacy allocation; RDAP registrant name unchanged since the original grant [Likely] — https://rdap.arin.net/registry/autnum/531

Country / RIR

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

Allocated

1989-09-29 (ARIN RDAP autnum top-level registration event, read from the correct top-level events[], not the entity-level POC/org decoy dates); last changed 2011-08-24 [Confirmed] — https://rdap.arin.net/registry/autnum/531

Website

Unknown — no operator-specific website found; the plausible successor page https://www.army.mil/usaisec returned HTTP 403 and could not be verified as authoritative for this ASN [Unknown] — https://rdap.arin.net/registry/autnum/531

Org status

RDAP status "active" (registry record not revoked); parent command USAISC was inactivated in 1996 per third-party history, so present-day administrative ownership beyond the RDAP registrant name is unclear [Likely] — https://rdap.arin.net/registry/autnum/531, https://en.wikipedia.org/wiki/United_States_Army_Information_Systems_Engineering_Command

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-10 — AS531 is absent from the live Spamhaus ASN-DROP feed, and no NANOG-archive or BGP hijack/route-leak tracker coverage references it; consistent with an unrouted legacy DoD ASN

Network & routing

Network type

U.S. military/government (DoD, Army) legacy DNIC-prefixed allocation from the pre-ARIN DDN NIC era, not a commercial ISP/enterprise network [Confirmed] — https://rdap.arin.net/registry/autnum/531

Historical routing

intermittently announced from 2010-08-27 (194.190.101.0/24) through 2023-07-28 (139.139.132.0/24) — dormant-but-previously-active, not a never-routed record [Confirmed] — https://stat.ripe.net/data/routing-status/data.json?resource=531

Peering

none found — no PeeringDB entry or public peering policy located; CAIDA degree is 0 across customer/peer/provider [Confirmed absence] — https://api.asrank.caida.org/v2/restful/asns/531

RPKI

not assessable — no current prefix announcements, so no route exists to validate against a ROA [Confirmed] — https://stat.ripe.net/data/rpki-validation/data.json?resource=531

Related ASNs

sibling low-numbered ASNs also registered to "Headquarters, USAISC" surfaced in search results (AS1451, AS1516, AS1539, AS1649); no shared parent org record confirmed in the canonical RDAP data [Likely] — https://bgp.tools/as/1649, https://bgp.tools/as/1516

Current routing

unrouted — 0 IPv4/IPv6 prefixes announced; 0 of 325 v4 and 0 of 322 v6 RIS peers see it; singleton customer cone (0 prefixes, 0 addresses); CAIDA degree total 0 (customer 0, peer 0, provider 0)

[Confirmed] — https://stat.ripe.net/data/routing-status/data.json?resource=531, https://api.asrank.caida.org/v2/restful/asns/531

Registrant/contacts

Headquarters, USAISC (org handle HEADQU-3), NETC-ANC CONUS TNOSC, Fort Huachuca, AZ 85613; tech/abuse/admin contact is the "Registration" group (REGIS10-ARIN) at DISA-Columbus, 300 North James Road, Whitehall, OH 43213, email disa.columbus.ns.mbx.arin-registrations@mail.mil

[Confirmed] — https://rdap.arin.net/registry/autnum/531

Analyst note

legacy DoD/DNIC allocation, RDAP-active but currently unrouted with a documented 2010–2023 window of intermittent BGP visibility; independently corroborated via a single bgp.tools fetch.