AS5972 — AS5972

AS5972 announces 343 IPv4 prefixes covering 1,864,192 addresses and 0 IPv6 prefixes.

About this network

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 214.0.0.0/8 alongside 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.

Announced prefixes

• 128.44.0.0/16
• 138.136.0.0/18
• 138.136.64.0/19
• 138.136.96.0/21
• 138.136.104.0/22
• 138.136.109.0/24
• 138.136.110.0/23
• 138.136.112.0/20
• 138.136.129.0/24
• 138.136.130.0/23
• 138.136.132.0/22
• 138.136.136.0/21
• 138.136.144.0/20
• 138.136.160.0/19
• 138.136.192.0/18
• 138.137.0.0/17
• 138.137.128.0/19
• 138.137.160.0/20
• 138.137.176.0/21
• 138.137.184.0/22
• 138.137.189.0/24
• 138.137.190.0/23
• 138.138.0.0/17
• 138.138.128.0/18
• 138.138.192.0/19
• 138.138.224.0/20
• 138.138.240.0/22
• 138.138.254.0/23
• 139.38.0.0/15
• 140.18.72.0/22
• 140.18.92.0/22
• 140.18.252.0/22
• 140.20.107.0/24
• 141.236.0.0/16
• 143.69.160.0/19
• 143.83.2.0/24
• 143.83.32.0/19
• 143.83.64.0/19
• 143.83.96.0/21
• 143.83.104.0/22
• 143.83.112.0/20
• 143.83.128.0/17
• 144.18.50.0/23
• 144.18.52.0/22
• 144.18.56.0/22
• 144.18.60.0/23
• 144.146.0.0/16
• 155.220.0.0/16
• 159.71.0.0/16
• 159.133.112.0/21
• 159.133.120.0/23
• 159.133.128.0/20
• 159.133.240.0/22
• 160.141.0.0/18
• 160.141.64.0/20
• 160.141.80.0/22
• 160.141.84.0/23
• 160.141.86.0/24
• 160.141.88.0/22
• 160.141.92.0/24
• 160.141.96.0/20
• 160.141.124.0/22
• 160.141.160.0/21
• 160.141.168.0/22
• 160.141.184.0/21
• 160.141.192.0/20
• 160.141.220.0/22
• 160.151.32.0/19
• 160.151.64.0/21
• 160.151.72.0/22
• 160.151.80.0/21
• 160.151.88.0/22
• 160.151.96.0/20
• 160.151.112.0/23
• 160.151.116.0/22
• 160.151.122.0/23
• 160.151.151.0/24
• 160.151.207.0/24
• 160.151.208.0/22
• 160.151.224.0/19
• 164.65.0.0/16
• 164.167.0.0/17
• 164.248.0.0/14
• 192.101.132.0/24
• 192.108.14.0/24
• 192.111.227.0/24
• 192.138.24.0/24
• 192.138.26.0/23
• 192.138.30.0/23
• 192.138.64.0/24
• 192.138.83.0/24
• 198.97.167.0/24
• 198.201.6.0/24
• 198.250.128.0/19
• 198.250.176.0/20
• 198.250.192.0/22
• 198.250.200.0/21
• 198.250.224.0/20
• 198.250.240.0/23
• 199.10.160.0/23

and 243 more.

Upstream networks

• AS27064 United States Department of Defense (DoD)
• AS27066 United States Department of Defense (DoD)
• AS27065 United States Department of Defense (DoD)

Adjacent networks

• AS27064 United States Department of Defense (DoD)
• AS27066 United States Department of Defense (DoD)
• AS27065 United States Department of Defense (DoD)