Which company owns MAC address prefix 44:59:9F?

MAC address prefix 44:59:9F is registered to Criticare Systems, Inc in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 44:59:9F has a network interface built by Criticare Systems, Inc.

What is the OUI 44:59:9F?

44:59:9F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Criticare Systems, Inc. It covers every address from 44:59:9F:00:00:00 to 44:59:9F:FF:FF:FF, or 16,777,216 addresses in total. It is also written 44-59-9F.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 44:59:9F:00:00:00 that is 44:59:9F — and look that prefix up in the IEEE OUI registry. If the second-lowest bit of the first octet is set, the address is locally administered (a randomized or private MAC), which belongs to no manufacturer and will not resolve; modern phones and laptops use these by default on each network.

Where is Criticare Systems, Inc located?

Criticare Systems, Inc is listed at 20925 Crossroads Circle Waukasha WI US 53186 in the IEEE OUI registry entry for 44:59:9F. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Criticare Systems, Inc

MAC address prefix 44:59:9F is registered to Criticare Systems, Inc in the IEEE OUI registry. Any device whose MAC address begins with 44:59:9F has a network interface built by Criticare Systems, Inc. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address — it covers every MAC from 44:59:9F:00:00:00 to 44:59:9F:FF:FF:FF.

OUI prefix: 44:59:9F
Hyphen form: 44-59-9F
MAC range: 44:59:9F:00:00:00 – 44:59:9F:FF:FF:FF
Addresses in block: 16,777,216
Organization: Criticare Systems, Inc
Address: 20925 Crossroads Circle Waukasha WI US 53186
Source: IEEE OUI registry

Have a full MAC address? Look it up— we'll also tell you if it's a randomized (private) address rather than a real manufacturer prefix.

Assignment history (2)

The IEEE registry publishes current state only — this is the change record we've kept since we started tracking it daily.

2016-07-29Assigned to "Criticare Systems, Inc"
archived source →
2026-07-17Assigned to "Criticare Systems, Inc"

Nearby in the registry

The prefixes assigned immediately before and after 44:59:9F:

FAQ

Which company owns MAC address prefix 44:59:9F?: MAC address prefix 44:59:9F is registered to Criticare Systems, Inc in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 44:59:9F has a network interface built by Criticare Systems, Inc.
What is the OUI 44:59:9F?: 44:59:9F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Criticare Systems, Inc. It covers every address from 44:59:9F:00:00:00 to 44:59:9F:FF:FF:FF, or 16,777,216 addresses in total. It is also written 44-59-9F.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 44:59:9F:00:00:00 that is 44:59:9F — and look that prefix up in the IEEE OUI registry. If the second-lowest bit of the first octet is set, the address is locally administered (a randomized or private MAC), which belongs to no manufacturer and will not resolve; modern phones and laptops use these by default on each network.
Where is Criticare Systems, Inc located?: Criticare Systems, Inc is listed at 20925 Crossroads Circle Waukasha WI US 53186 in the IEEE OUI registry entry for 44:59:9F. This is the address the organization registered with the IEEE, which may differ from its current operating address.