AS356

AS356 is a legacy autonomous system number registered under ARIN to the United States Department of Defense (ARIN org handle USDDD) and administered by DISA-Columbus, the Defense Information Systems Agency facility in Whitehall, Ohio. It does not resolve to an individually-delegated RDAP record: ARIN serves it as part of the contiguous DNIC block DNIC-ASBLK-00306-00371, which spans AS306 through AS371 and was registered on 1989-06-30 — one of the earliest ASN blocks reserved for DoD networks. That block-level registration date is the correct top-level allocation event for any ASN in the range, and bgp.tools independently lists AS356 itself as "registered on June 30, 1989," an exact match. Unlike the dormant legacy ASNs common in this era, AS356 is actively routed: RIPEstat and bgp.tools report roughly 111–114 announced IPv4 prefixes totalling about 131,072 addresses (a /16-equivalent, drawn from 55.x space) and zero IPv6. It behaves as a single-homed stub — RIPEstat observes a single neighbour and bgp.tools reports one upstream, consistent with an internally-routed government network rather than an Internet-peering transit AS. No public abuse, hijack, or route-leak signal specifically names AS356 as of 2026-07-01. The only adjacent security narrative — the 2021 announcement of dormant DoD IPv4 space — is attributed by every source to AS8003 (Global Resource Systems LLC), not AS356, and must not be reported as an AS356 incident. A critical disambiguation: AS356 is distinct from AS3356 (Lumen/Level 3), the far larger transit ASN behind the August 2020 CenturyLink outage.

Operator

United States Department of Defense (DoD); ARIN org handle USDDD, administered by DISA-Columbus, 300 North James Road, Whitehall, OH 43213 [Confirmed] — ARIN RDAP autnum/356 (registrant entity)

Country / RIR

US, ARIN [Confirmed] — ARIN RDAP autnum/356; RIPEstat as-overview (block "Assigned by ARIN")

Allocated

1989-06-30 (ARIN registry top-level registration event for the DNIC-ASBLK-00306-00371 block containing AS356 — a first-party RIR fact, NOT an IEEE date); last changed 2025-09-12 [Confirmed] — ARIN RDAP autnum top-level events[]; corroborated by bgp.tools "registered on June 30, 1989"

Org status

active — ARIN RDAP status "active" on the containing DNIC block; USDDD = United States Department of Defense, a cabinet-level federal executive department [Confirmed] — ARIN RDAP autnum/356

Contacts

NOC/technical/abuse handle MIL-HSTMST-ARIN, disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil; registration handle REGIS10-ARIN, disa.columbus.ns.mbx.arin-registrations@mail.mil [Confirmed] — ARIN RDAP autnum/356

Website

no dedicated AS356 operator website first-party-confirmed this session; DoD NIC portal (nic.mil) and DISA (www.disa.mil) were unreachable from this environment [Unknown]

Security/abuse context (NEUTRAL, DATED)

no notable public abuse signal specifically naming AS356 found as of 2026-07-01 — not in Spamhaus/AbuseIPDB/IPQualityScore searches, NANOG archives, or BGP-incident retrospectives; CleanTalk shows 55.48.0.0/16 at 0.00% spam

Network & routing

Network type

U.S. federal government / military network; single-homed stub, does not provide transit — a government end-user/enterprise network, not a commercial ISP [Likely] — ipinfo.io/AS356, bgp.tools/as/356

Size

~111–114 announced IPv4 prefixes / ~131,072 IPv4 addresses (/16-equivalent, from 55.48.0.0/16 and 55.89.0.0/16 space); 0 IPv6 prefixes [Confirmed] — RIPEstat routing-status (stat.ripe.net/AS356), bgp.tools/as/356

Routing/peering

single-homed stub; RIPEstat observes 1 total neighbour; bgp.tools reports 1 upstream (name not surfaced this pass) [Likely]; no published formal peering policy located; DISA's DISN Connection Process Guide documents DoD NIC IP registration but is not a peering policy

[Unknown for named peers/upstream] — stat.ripe.net/AS356, bgp.tools/as/356

RPKI

not determined — RIPEstat rpki-validation is per-prefix and was skipped (no prefix supplied); no ROA coverage figure obtained [Unknown] — stat.ripe.net/AS356

Notable usage

part of the historic DNIC ASN block reserved for DoD networks administered by DISA-Columbus; associated 55.x address space includes at least one /24 (55.89.1.0/24) sub-registered to Headquarters, USAISC (U.S. Army Information Systems Command), Fort Huachuca, AZ, indicating military enterprise/tactical usage

[Likely] — ipinfo.io/AS356, ipinfo.io/AS356/55.89.1.0/24

Registry name

DNIC-ASBLK-00306-00371 (block range AS306–AS371); bgp.tools labels AS356 individually as "DoD Network Information Center" [Confirmed] — ARIN RDAP; bgp.tools/as/356

Sector context (NOT an AS356 incident)

the 2021 "DoD IPv4 honeypot" BGP announcements of dormant DoD space were originated by AS8003 (Global Resource Systems LLC), not AS356; no evidence AS356 was hijacked or used as a route-leak vector [Confirmed] — kentik.com/blog/the-mystery-of-as8003, theregister.com 2021-04-26

Disambiguation

AS356 (DoD DNIC, 131k IPv4) is DISTINCT from AS3356 (Lumen/Level 3), the transit ASN in the August 2020 CenturyLink/Level 3 outage; entity-nested contact dates (1993-05-26, 2009-06-24, 2026-02-12) are contact-record dates, not the ASN's allocation/update dates, and were excluded

[Confirmed] — ARIN RDAP; blog.cloudflare.com CenturyLink/Level 3 analysis

Analyst note

Encountered as an actively-routed legacy DoD DNIC-block ASN. RDAP resolves to the block record (AS306-AS371); the block's top-level events are the correct allocation dates for AS356. Clean, no direct abuse signal.