Which company owns MAC address prefix C4:A5:59?

MAC address prefix C4:A5:59 is registered to IEEE Registration Authority in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C4:A5:59 has a network interface built by IEEE Registration Authority.

What is the OUI C4:A5:59?

C4:A5:59 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to IEEE Registration Authority. It covers every address from C4:A5:59:00:00:00 to C4:A5:59:FF:FF:FF, or 16,777,216 addresses in total. It is also written C4-A5-59.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in C4:A5:59:00:00:00 that is C4:A5:59 — 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 IEEE Registration Authority located?

IEEE Registration Authority is listed at 445 Hoes Lane Piscataway NJ US 08554 in the IEEE OUI registry entry for C4:A5:59. This is the address the organization registered with the IEEE, which may differ from its current operating address.

IEEE Registration Authority

MAC address prefix C4:A5:59 is registered to IEEE Registration Authority in the IEEE OUI registry. Any device whose MAC address begins with C4:A5:59 has a network interface built by IEEE Registration Authority. 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 C4:A5:59:00:00:00 to C4:A5:59:FF:FF:FF.

OUI prefix: C4:A5:59
Hyphen form: C4-A5-59
MAC range: C4:A5:59:00:00:00 – C4:A5:59:FF:FF:FF
Addresses in block: 16,777,216
Organization: IEEE Registration Authority
Address: 445 Hoes Lane Piscataway NJ US 08554
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 (1)

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

2026-07-17Assigned to "IEEE Registration Authority"

Nearby in the registry

The prefixes assigned immediately before and after C4:A5:59:

FAQ

Which company owns MAC address prefix C4:A5:59?: MAC address prefix C4:A5:59 is registered to IEEE Registration Authority in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C4:A5:59 has a network interface built by IEEE Registration Authority.
What is the OUI C4:A5:59?: C4:A5:59 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to IEEE Registration Authority. It covers every address from C4:A5:59:00:00:00 to C4:A5:59:FF:FF:FF, or 16,777,216 addresses in total. It is also written C4-A5-59.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in C4:A5:59:00:00:00 that is C4:A5:59 — 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 IEEE Registration Authority located?: IEEE Registration Authority is listed at 445 Hoes Lane Piscataway NJ US 08554 in the IEEE OUI registry entry for C4:A5:59. This is the address the organization registered with the IEEE, which may differ from its current operating address.