AS340

AS340 is a legacy autonomous system number registered under ARIN to the United States Department of Defense (DoD). It does not hold its own standalone registry object: ARIN serves AS340 as part of the DoD ASN block DNIC-ASBLK-00306-00371 (autnum handle AS306), which spans AS306 through AS371 and was registered on 1989-06-30 — placing it among the oldest blocks in the global ASN space. The registrant org is the DoD (ARIN org handle USDDD), and the administrative, NOC, technical, and abuse contacts all route through the Defense Information Systems Agency (DISA) office in Columbus, Ohio. Operationally, AS340 is a single-homed stub network: every public BGP source observes exactly one neighbour, AS306 (also DoD), and the ASN provides no transit. Its prefixes live in the DoD-assigned 55.0.0.0/8 IPv4 space — three /16s (55.40.0.0/16, 55.73.0.0/16, 55.86.0.0/16) plus smaller sub-blocks, roughly 196,608 IPv4 addresses, alongside one IPv6 prefix (2608:14b:4500::/40). BGP table descriptions read "Headquarters, USAISC" (U.S. Army Information Systems Command), suggesting the block supports U.S. Army information-systems infrastructure. As of 2026-06-28 RIPEstat reports the ASN is not currently announcing — its prefix timelines last show activity ending 2026-06-26 — consistent with intermittent or recently-withdrawn routing on a closed military network. No PeeringDB record exists, zero public domains are hosted, and no notable abuse signal was found across Spamhaus ASN-DROP, AbuseIPDB, GreyNoise, or NANOG archives — consistent with a government-internal AS that does not participate in public peering or reputation systems.

Operator

United States Department of Defense (DoD) — ARIN registrant org handle USDDD; managed by DISA-Columbus (Defense Information Systems Agency) [Confirmed] — ARIN RDAP autnum/340, ipinfo.io/AS340

Country / RIR

US, ARIN [Confirmed] — ARIN RDAP autnum/340

Allocated

1989-06-30 (ARIN registry date for block DNIC-ASBLK-00306-00371; a first-party RIR fact, NOT an IEEE date); last changed 2025-09-12 [Confirmed] — ARIN RDAP autnum top-level events

ASN block

AS340 falls within the DoD block DNIC-ASBLK-00306-00371 (autnum handle AS306, covering AS306–AS371); the RDAP /autnum/340 endpoint resolves to the parent block object [Confirmed] — ARIN RDAP autnum/340

Org status

active U.S. federal government agency (DoD); block record DNIC-ASBLK-00306-00371 is active [Confirmed] — ARIN RDAP autnum/340

Contacts

DISA Columbus — hostmaster disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil; registrations disa.columbus.ns.mbx.arin-registrations@mail.mil; +1-844-347-2457 ext 2; 300 North James Road, Whitehall, OH 43213 (registrant org address 3990 E. Broad Street, Columbus, OH 43218)

[Confirmed] — ARIN RDAP autnum/340

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal found as of 2026-06-28 — not in Spamhaus ASN-DROP (425-entry feed, not listed), AbuseIPDB (no accessible record, HTTP 403), GreyNoise blog, or NANOG archives; consistent with a government-internal AS

Network & routing

Network type

government stub AS — single-homed, provides no transit; sole observed peer/upstream is AS306 (also DoD) [Confirmed] — ipinfo.io/AS340, bgp.he.net/AS340, bgp.tools/as/340

Size

~196,608 IPv4 addresses across three /16s (55.40.0.0/16, 55.73.0.0/16, 55.86.0.0/16; the /19 and /24 entries are subsets) plus one IPv6 prefix 2608:14b:4500::/40 [Likely] — RIPEstat announced-prefixes, ipinfo.io/AS340

Routing/peering

7 IPv4 + 1 IPv6 recently-active prefixes (window 2026-06-14 to 2026-06-26); 1 observed neighbour (AS306); NOT currently announced as of 2026-06-28 (as-overview announced: false)

[Confirmed] — RIPEstat as-overview / announced-prefixes / routing-status; RIS visibility when active 324/326 v4, 324/324 v6

Peering policy

no PeeringDB record found (HTTP 404); no public peering policy — all observed BGP sessions are internal to DoD (AS306 only) [Likely] — bgp.he.net/AS340, bgp.tools/as/340

RPKI

Unknown — RIPEstat RPKI validation requires a supplied prefix; not assessed for these specific 55.x prefixes [Unknown] — no source

Upstreams / AS rank / customer cone

Unknown — not present in available routing-status / CAIDA source data [Unknown] — no source

Notable usage

all AS340 prefix descriptions in BGP tables read "Headquarters, USAISC" (U.S. Army Information Systems Command); zero hosted public domains; bgp.he.net carries a bogon annotation (a routing-data flag, not an organizational finding) [Confirmed] — bgp.he.net/AS340, ipinfo.io/AS340, bgp.tools/as/340

Related ASNs

AS306 (sole BGP peer/upstream, also DoD; the block's autnum handle) [Confirmed] — ARIN RDAP autnum/340, bgp.tools/as/340

Analyst note

Encountered as a legacy DoD stub ASN served via a shared block object. The decoy entity-level registration dates (1993-05-26 for the MIL-HSTMST-ARIN contact, 2009-06-24 for REGIS10-ARIN, 2007-01-12 for the USDDD org) are contact/org events, NOT the allocation date; the authoritative allocated_date is the autnum top-level registration event 1989-06-30.