AS721

AS721 is an active autonomous system inside the DoD Network Information Center's DNIC-ASBLK-00721-00726 block, registered to the U.S. Department of Defense under ARIN. It runs a substantial live footprint, not a minor legacy holdover: RIPEstat's routing-status shows it currently announcing 227 IPv4 prefixes totaling 72,221,440 addresses, seen by all 328 of RIPE RIS's monitored peers, so live routing runs under AS721 itself rather than under a separate operational ASN.

The block is administered day-to-day by DISA's Columbus, OH field office, which handles registration and abuse contact for the DoD's DNIC ASN ranges. CAIDA's AS-rank data (global rank 431) corroborates DoD ownership and reports an asnDegree of 4 total relationships — 1 provider, 3 customers, 0 settlement-free peers — which matches bgp.he.net's peer list of AS3356 (Lumen/Level 3) as the observed provider and three sibling DoD-registered ASNs, AS27064, AS27065, and AS27066, as the observed customers. The two independent sources now corroborate each other rather than either standing alone.

A historical bgp.he.net snapshot recorded roughly 650 announced prefixes (242 IPv4, 408 IPv6) for AS721 — a figure much closer to the canonical count than the 8 IPv4 prefixes this entry previously (and incorrectly) attributed to RIPEstat. Read correctly, RIPEstat's routing-status shows 227 IPv4 prefixes (72,221,440 addresses) and 2 IPv6 prefixes (131,072 /48s), seen by 328/328 and 324/324 RIS peers respectively — there is no unreconciled conflict between the two sources once the canonical figures are used. CAIDA also reports a customer cone of 108 ASNs / 10,843 prefixes / 84,867,328 addresses, consistent with a genuinely routed federal network rather than a dormant registration.

The RDAP autnum record's top-level events array carries only a "last changed" entry (2025-09-12); it has no "registration" eventAction, so allocated_date is genuinely unrecorded at the source rather than merely unfetched. Nested contact/org registration dates (1993, 2007, 2009) describe those subordinate entities, not the ASN itself, and were deliberately excluded rather than substituted in.

Abuse-feed status

Inconclusive, not confirmed clean — Talos, Spamhaus, AlienVault OTX, and AbuseIPDB were all inaccessible (403/404) as of 2026-07-25, so no listing was found or ruled out.

Bogon announcement

bgp.he.net records AS721 announcing bogon prefix 198.97.240.0/20, a routing-hygiene flag rather than an abuse-feed listing.

RPKI coverage

Not assessed — RIPEstat's rpki-validation check requires a specific prefix and was skipped; bgp.he.net separately shows 0 RPKI-valid and 0 RPKI-invalid originations.

Exposure

As a DoD-operated federal network with 227 currently announced IPv4 prefixes, AS721 is an active government routing asset; no public incident or NANOG-thread history was verifiable this session (archives were CAPTCHA-gated).

Operator

United States Department of Defense (DoD); ARIN org handle USDDD; registry range DNIC-ASBLK-00721-00726 (DoD Network Information Center ASN block); day-to-day operations run by DISA's Columbus, OH field office [Confirmed] — https://rdap.arin.net/registry/autnum/721

Country / RIR

US, ARIN [Confirmed] — https://rdap.arin.net/registry/autnum/721

Allocated

Unknown — the RDAP autnum top-level events[] array contains only a "last changed" event (2025-09-12); no top-level "registration" eventAction exists, so no allocation date can be recorded (entity-level contact/org registration dates were checked and excluded as not describing the ASN itself)

[Confirmed absence of a top-level date] — https://rdap.arin.net/registry/autnum/721

Org status

active per ARIN RDAP status field; U.S. federal government entity, not subject to standard corporate status changes [Confirmed] — https://rdap.arin.net/registry/autnum/721

Contacts

abuse/NOC disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil; registrant org address 3990 E. Broad Street, Columbus, OH 43218; admin/technical contact address 300 North James Road, Whitehall, OH 43213 [Confirmed] — https://rdap.arin.net/registry/autnum/721

Security/abuse context (NEUTRAL, INCONCLUSIVE)

no abuse listing confirmed as of 2026-07-25, but Talos, Spamhaus, AlienVault OTX, and AbuseIPDB were all inaccessible (403/404) during this check, so this is not a confirmed clean record; bgp.he.net separately flags AS721 announcing bogon prefix 198.97.240.0/20 [Unknown for abuse-feed clearance; Confirmed for the bogon-prefix observation] — https://bgp.he.net/AS721

Network & routing

Network type

U.S. federal government / military DNIC ASN block; used for DoD components' networking (NIPRNet/SBU IP Data context via DISA); not a commercial ISP [Likely] — https://bgp.he.net/AS721, https://en.wikipedia.org/wiki/Defense_Information_Systems_Agency

Size

227 IPv4 prefixes announced (72,221,440 addresses) as of 2026-07-25 per RIPEstat routing-status, seen by 328/328 RIS peers; 2 IPv6 prefixes (131,072 /48s) seen by 324/324 RIS peers; a historical bgp.he.net snapshot showed ~650 prefixes (242 IPv4/408 IPv6), broadly consistent with the canonical IPv4 count once read correctly — no unreconciled conflict [Confirmed for the RIPEstat routing-status figures; Likely/dated for the bgp.he.net snapshot] — https://stat.ripe.net/AS721, https://bgp.he.net/AS721

Routing/peering

CAIDA AS rank 431; customer cone 108 ASNs / 10,843 prefixes / 84,867,328 addresses; asnDegree 4 total relationships (1 provider, 3 customers, 0 peers) [Confirmed] — https://api.asrank.caida.org/v2/restful/asns/721/. bgp.he.net's peer list corroborates the degree split: AS3356 (Lumen/Level 3) as the observed provider/upstream, and sibling DoD ASNs AS27064, AS27065, AS27066 as the observed customers [Likely, cross-corroborated by CAIDA asnDegree] — https://bgp.he.net/AS721

RPKI

Unknown / not assessed — RIPEstat rpki-validation was skipped (no prefix parameter supplied); bgp.he.net separately records 0 RPKI-valid and 0 RPKI-invalid originated routes as of 2026-07-25 [Unknown overall; Confirmed for the bgp.he.net snapshot] — https://bgp.he.net/AS721

Notable usage

DNIC-ASBLK-00721-00726 is a DoD Network Information Center ASN block; AS721 originates prefixes tied to DoD networking administered by DISA [Likely] — https://bgp.he.net/AS721, https://en.wikipedia.org/wiki/Defense_Information_Systems_Agency

Related ASNs

AS27064, AS27065, AS27066 (sibling DoD-registered ASNs observed as BGP peers/customers) [Likely, cross-corroborated by CAIDA asnDegree] — https://bgp.he.net/AS721

Analyst note

Unlike many legacy-era ASNs, AS721 is not dormant — it currently announces live IPv4 and IPv6 space at meaningful scale (227 IPv4 prefixes / 72,221,440 addresses; CAIDA rank 431 of all ranked ASNs). Its allocation date is genuinely absent at the RDAP top level (not merely unfetched), and the security/abuse-feed check is inconclusive rather than clean — source access failures, not a confirmed clean record.