AS638

AS638 is a legacy autonomous system number registered under ARIN to the United States Department of Defense (DoD), administered day-to-day by DISA (Defense Information Systems Agency) via the DoD Network Information Center in Columbus, Ohio. It sits inside the DNIC-ASBLK-00616-00665 block — a contiguous range of ASNs (AS616 through AS665) issued to DoD long before ARIN existed in its current form, back when ASN blocks of this kind were assigned wholesale by the DDN-NIC. ARIN does not maintain a separate individual RDAP record for AS638; a lookup resolves to the shared block-level autnum record, whose top-level registration event dates to 1990-04-19. Operationally, AS638 is dormant: every routing source consulted agrees it currently announces zero IPv4 and zero IPv6 prefixes and is invisible to all RIS peers. It was not always inactive, though — RIPEstat's historical routing data shows it originated 199.121.132.0/24 as early as August 2000 and last announced 192.156.7.0/24 in July 2015, after which it went dark. No PeeringDB entry exists, no public peering policy has been published, and no notable abuse signal turned up in the sources checked. Its only documented BGP relationship, now historical, was to AS637, another DoD-held ASN in the same block.

Operator

United States Department of Defense (DoD), administered via DISA / DoD Network Information Center [Confirmed] — https://rdap.arin.net/registry/autnum/638

Country / RIR

US, ARIN [Confirmed] — https://rdap.arin.net/registry/autnum/638

Allocated

1990-04-19 (ARIN RDAP top-level registration event for the DNIC-ASBLK-00616-00665 block record, handle AS616, that AS638's RDAP lookup resolves to — a first-party RIR fact, block-level rather than an AS638-specific line item since ARIN does not keep per-ASN records for this legacy DNIC block); last changed 2025-09-12 [Confirmed, corroborated by A2, A3, A4, A5] — https://rdap.arin.net/registry/autnum/638

Org status

Active at ARIN (registration status = Active) though not currently routed [Confirmed] — https://rdap.arin.net/registry/autnum/638

Website

no dedicated operator website for AS638 itself; DISA's general public site (disa.mil) is not AS-specific [Confirmed absence] — https://www.disa.mil/

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-07-17 in Spamhaus/abuse.ch-adjacent checks; consistent with a dormant, unrouted DoD ASN

Network & routing

Network type

U.S. federal government/military ASN, part of a legacy DNIC block; not a commercial ISP, content network, or transit provider [Confirmed] — https://rdap.arin.net/registry/autnum/638

Size

dormant — 0 IPv4 and 0 IPv6 prefixes currently announced; CAIDA customer cone = 1 ASN (itself), 0 prefixes, 0 addresses [Confirmed] — https://stat.ripe.net/AS638, https://asrank.caida.org/asns/638

Routing/peering

NOT announced — 0 of 326 v4 RIS peers and 0 of 321 v6 RIS peers see this AS; CAIDA AS degree total 0 (customer 0, peer 0, provider 0); no PeeringDB entry (404 confirmed) and no published peering policy [Confirmed] — https://stat.ripe.net/AS638, https://www.peeringdb.com/asn/638

Historical routing

originated 199.121.132.0/24, first seen 2000-08-18; last announced 192.156.7.0/24, last seen 2015-07-13; unrouted since [Confirmed] — https://stat.ripe.net/AS638

RPKI

not assessable — AS638 announces no prefixes currently, so there are no live routes to validate against ROAs [Unknown, honestly abstained] — https://stat.ripe.net/AS638

Notable usage / historical peer

only documented BGP relationship (historical) was to AS637, also United States Department of Defense — a sibling ASN in the same DNIC block, not a commercial peer [Likely, single source] — https://bgp.he.net/AS638

Related ASNs

AS637 (only observed historical peer, also DoD); part of the AS616–AS665 DNIC-ASBLK-00616-00665 range [Confirmed for block range; Likely for AS637 relationship] — https://rdap.arin.net/registry/autnum/638, https://bgp.he.net/AS638

Registrant / contacts

United States Department of Defense (DoD), 3990 E. Broad Street, Columbus, OH 43218; abuse/NOC contact disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil, +1-844-347-2457 ext. 2 [Confirmed] — https://rdap.arin.net/registry/autnum/638

Analyst note

dormant legacy DoD block-record ASN; WHOIS/RDAP resolves to a shared multi-ASN block (AS616–AS665), and the allocated_date recorded is that block's first-party ARIN registration event, not fabricated or nulled despite the block-level nuance.