Which company owns MAC address prefix A4:F5:22?

MAC address prefix A4:F5:22 is registered to CHOFU SEISAKUSHO CO.,LTD in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with A4:F5:22 has a network interface built by CHOFU SEISAKUSHO CO.,LTD.

What is the OUI A4:F5:22?

A4:F5:22 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to CHOFU SEISAKUSHO CO.,LTD. It covers every address from A4:F5:22:00:00:00 to A4:F5:22:FF:FF:FF, or 16,777,216 addresses in total. It is also written A4-F5-22.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in A4:F5:22:00:00:00 that is A4:F5:22 — 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 CHOFU SEISAKUSHO CO.,LTD located?

CHOFU SEISAKUSHO CO.,LTD is listed at 2-1 Shimonoseki-shi Yamaguchi JP 752-8555 in the IEEE OUI registry entry for A4:F5:22. This is the address the organization registered with the IEEE, which may differ from its current operating address.

CHOFU SEISAKUSHO CO.,LTD

MAC address prefix A4:F5:22 is registered to CHOFU SEISAKUSHO CO.,LTD in the IEEE OUI registry. Any device whose MAC address begins with A4:F5:22 has a network interface built by CHOFU SEISAKUSHO CO.,LTD. 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 A4:F5:22:00:00:00 to A4:F5:22:FF:FF:FF.

OUI prefix: A4:F5:22
Hyphen form: A4-F5-22
MAC range: A4:F5:22:00:00:00 – A4:F5:22:FF:FF:FF
Addresses in block: 16,777,216
Organization: CHOFU SEISAKUSHO CO.,LTD
Address: 2-1 Shimonoseki-shi Yamaguchi JP 752-8555
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 "CHOFU SEISAKUSHO CO.,LTD"
archived source →
2026-07-17Assigned to "CHOFU SEISAKUSHO CO.,LTD"

Nearby in the registry

The prefixes assigned immediately before and after A4:F5:22:

FAQ

Which company owns MAC address prefix A4:F5:22?: MAC address prefix A4:F5:22 is registered to CHOFU SEISAKUSHO CO.,LTD in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with A4:F5:22 has a network interface built by CHOFU SEISAKUSHO CO.,LTD.
What is the OUI A4:F5:22?: A4:F5:22 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to CHOFU SEISAKUSHO CO.,LTD. It covers every address from A4:F5:22:00:00:00 to A4:F5:22:FF:FF:FF, or 16,777,216 addresses in total. It is also written A4-F5-22.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in A4:F5:22:00:00:00 that is A4:F5:22 — 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 CHOFU SEISAKUSHO CO.,LTD located?: CHOFU SEISAKUSHO CO.,LTD is listed at 2-1 Shimonoseki-shi Yamaguchi JP 752-8555 in the IEEE OUI registry entry for A4:F5:22. This is the address the organization registered with the IEEE, which may differ from its current operating address.