AS491

AS491 is part of a large legacy autonomous-system block, AFCONC-BLOCK1-AS, spanning AS379 through AS508 and registered under ARIN to Air Force Systems Networking (ARIN org handle 7ESG), headquartered at 501 East Moore Drive, Gunter Annex, Maxwell AFB, Alabama. Because the RIR issued this range as a single shared record rather than individual per-ASN registrations, AS491 has no standalone RDAP entry; its authoritative facts — registration date, registrant, and status — come from the block-level autnum record. That top-level record shows a registration event of 1989-08-04 and a last-changed date of 2008-06-06, with administrative, technical, and abuse contact handled by DISA-Columbus. Third-party AS-name registries (cidr-report.org) label the block "Headquarters Standard Systems Center," a real U.S. Air Force data-processing organization once headquartered at Gunter Annex — a different, more specific attribution than the tentative "754th Electronic Systems Group" label used for its block-mate AS489, and neither is an ARIN RDAP field. AS491 is currently dormant: RIPEstat shows zero announced IPv4 or IPv6 prefixes, and it last appeared in global BGP routing tables on 2020-12-07 (prefix 137.2.128.0/19), having first been observed announcing 132.56.0.0/16 back on 2001-09-26. CAIDA AS Rank places it at 79,459 with zero peers, zero upstreams, and a singleton customer cone, and PeeringDB confirms AS491 does not appear among the five member ASNs listed under the "Air Force Systems Networking" org profile. No notable public abuse signal was found in Spamhaus, NANOG archives, or general threat-intel searches, consistent with a dormant U.S. federal military network with minimal public footprint.

Operator

Air Force Systems Networking (ARIN org handle 7ESG); registrant of the shared block AFCONC-BLOCK1-AS (AS379–AS508) covering AS491; no standalone RDAP record exists for AS491 itself [Confirmed] — https://rdap.arin.net/registry/autnum/491

Country / RIR

US, ARIN [Confirmed] — https://rdap.arin.net/registry/autnum/491, https://stat.ripe.net/AS491

Allocated

1989-08-04 (ARIN top-level registration event on the AFCONC-BLOCK1-AS autnum record — the sole RDAP record covering AS491); last changed 2008-06-06 [Confirmed] — https://rdap.arin.net/registry/autnum/491

Org status

active per ARIN RDAP (status: active on the containing AFCONC-BLOCK1-AS block record, the only record covering AS491); registrant of record is 7ESG / Air Force Systems Networking; administrative/technical/abuse contact consolidated under DISA-Columbus

[Confirmed] — https://rdap.arin.net/registry/autnum/491

Contacts

disa.columbus.ns.mbx.arin-registrations@mail.mil (handle REGIS10-ARIN); registrant address 501 East Moore Dr, Bldg 884 Rm 1100, Gunther Annex, Maxwell AFB, AL 36114 [Confirmed] — https://rdap.arin.net/registry/autnum/491

Website

no dedicated official website found for AS491 or a specific operating unit tied to it by name [Unknown, sourced null] — https://ipinfo.io/AS491

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-10 — not identified in Spamhaus DROP/ASN-DROP, no NANOG archive hits, no ASN-specific hits in general AbuseIPDB/GreyNoise/threat-feed searches; consistent with a dormant military ASN

Network & routing

Network type

U.S. military/government network (Air Force Systems Networking / DISA-Columbus contact); not a commercial ISP or transit provider [Likely] — https://rdap.arin.net/registry/autnum/491

Size

dormant — 0 IPv4 prefixes / 0 IPv6 prefixes currently announced; customer cone = 1 ASN (itself), 0 prefixes, 0 addresses [Confirmed] — https://stat.ripe.net/AS491, https://asrank.caida.org/

Routing/peering

NOT currently announced — 0 of 327 v4 RIS peers and 0 of 321 v6 RIS peers see this AS; CAIDA degree total 0 (customer 0, peer 0, provider 0); PeeringDB org 20118 ("Air Force Systems Networking") lists AS123, AS65, AS175, AS221, and AS301 as members but NOT AS491

[Confirmed] — https://stat.ripe.net/AS491, https://www.peeringdb.com/org/20118

Historical routing

first seen announcing 132.56.0.0/16 on 2001-09-26; last seen announcing 137.2.128.0/19 on 2020-12-07 [Confirmed] — https://stat.ripe.net/AS491

RPKI

not assessable — AS491 announces no prefixes, so there are no ROAs to validate [Confirmed] — https://stat.ripe.net/AS491

Notable usage

no AS491-specific traffic or usage narrative found; IPinfo shows 0 IPv4/IPv6 addresses and 0 hosted domains for AS491 [Confirmed, sourced null] — https://ipinfo.io/AS491

Related ASNs

part of shared block AFCONC-BLOCK1-AS, range AS379–AS508; block-mates already documented under the same registrant include AS486 and AS489, tagged identically by third-party AS-name registries [Confirmed] — https://rdap.arin.net/registry/autnum/491, https://www.cidr-report.org/as4637/autnums.html

Specific operating unit

third-party AS-name lists (cidr-report.org) tag the block "AFCONC-BLOCK1-AS - Headquarters Standard Systems Center," a historical USAF data-processing organization at Gunter Annex, Maxwell AFB — consistent with the registrant address but not an ARIN RDAP field; distinct from the tentative "754th Electronic Systems Group" label used for block-mate AS489

[Likely] — https://www.cidr-report.org/as4637/autnums.html

Analyst note

AS491 has no standalone ARIN record — it is one of ~130 ASNs (AS379–AS508) sharing a single legacy block registered to Air Force Systems Networking. Dormant since 2020; two competing third-party unit-name attributions exist across block-mates ("Headquarters Standard Systems Center" vs. "754th Electronic Systems Group") and neither is authoritative.