Autonomous system
AS5972 AS5972
Unclassified ARIN
Summary
US Department of Defense — Military Health System
government military legacy
A US Department of Defense network from the block DNIC-ASBLK-05800-06055, registered to the DoD Network Information Center (DNIC). Its address space is used by the Military Health System — reverse DNS across the AS resolves overwhelmingly under health.mil and mhsi.med.osd.mil.
What it's used for
- Networking for DoD military medicine: military treatment facilities, hospitals and clinics, and the supporting health-IT infrastructure run under the Defense Health Agency.
- It is one of the largest ASNs in the DoD block by address count, announcing well over a thousand prefixes and roughly 1.9 million IPv4 addresses.
Notable
- A government / DoD network, not a commercial ISP or host.
- The inventory is unusually diverse for a single AS: it aggregates space from the DoD-held
214.0.0.0/8alongside a long list of legacy/16s (138.x,139.x,144.146.x,160.x,164.250.x,199.x), all consistently named for health-system use. - Reverse DNS names identify individual sites (for example Fort Sam Houston and Beale AFB), which is a good reminder that even DoD ranges leak topology through PTR records.
Interesting
- Health care is why a "military" AS is one of the biggest in the DoD block: hospitals and clinics need far more endpoint addressing than a typical operational network, so the medical enterprise ends up with an outsized share of DoD address space.
This description is AI-generated, best-effort context — not authoritative, and provided without any guarantee of accuracy. Source, and how to suggest an edit.
Interconnection
Peering at a glance
Internet exchanges
No exchange port on file. Many exchanges publish no participant list, so this is not proof of absence.
Exchange presence is recorded rather than inferred: the directory collected by Packet Clearing House (https://www.pch.net/ixp/data) on 2026-10-21, licensed CC BY-NC-SA 3.0. Transit is inferred from observed BGP paths, never declared by either party.
Address space
Summary
IPv4 544 prefixes · 1.86M addresses IPv6 0 prefixes
| Country | Name | Prefixes |
|---|---|---|
| Unknown | 544 |
Registry
Allocation record
- Registry
- ARIN
- Handle
AS5800- Registry name
- DNIC-ASBLK-05800-06055
- Registrant
- United States Department of Defense (DoD)
- Abuse contact
- disa.columbus.ns.mbx.hostmaster-dod-nic@mail.mil
- Registered
- 1995-10-24
- Last changed
- 2025-09-12
- Allocation
- assigned
Routing security
RPKI and IRR
- RPKI
- 0% valid · 0 valid, 1,480 with no ROA
- ROAs
- 0 authorising AS5972
- ASPA
- no ASPA record
- IRR
- 0.3% registered · 4 of 1,480 announcements
- Route objects
- 9 naming AS5972
Reputation
Classification and threat
Unclassified Not in the curated lists. Most of the ~80,000 allocated ASNs are not.
Spamhaus DROP
Not on ASN-DROP The network as a whole is not listed.
No DROP prefixes None of its announced space is on the DROP prefix list.
Spamhaus DROP ("Don't Route Or Peer") lists space and networks run by, or hijacked for, spam and cybercrime operations: 442 networks and 1,779 prefixes, as published 2026-10-22. A short, high-confidence list, so a match is worth taking seriously, and absence from it says little on its own.
FBI IC3
No IC3 indicators Nothing from the FBI IC3 feed.
IC3 threat data is alpha. Absence of an indicator is not evidence of good behaviour, only of absence from this one feed.
Elsewhere