Which company owns MAC address prefix 40:04:0C?

MAC address prefix 40:04:0C is registered to A&T in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 40:04:0C has a network interface built by A&T.

What is the OUI 40:04:0C?

40:04:0C is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to A&T. It covers every address from 40:04:0C:00:00:00 to 40:04:0C:FF:FF:FF, or 16,777,216 addresses in total. It is also written 40-04-0C.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 40:04:0C:00:00:00 that is 40:04:0C — 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 A&T located?

A&T is listed at #411, Will Town, 402-3 Bucheon-Si Gyeonggi-Do KR 420-814 in the IEEE OUI registry entry for 40:04:0C. This is the address the organization registered with the IEEE, which may differ from its current operating address.

A&T

MAC address prefix 40:04:0C is registered to A&T in the IEEE OUI registry. Any device whose MAC address begins with 40:04:0C has a network interface built by A&T. 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 40:04:0C:00:00:00 to 40:04:0C:FF:FF:FF.

OUI prefix: 40:04:0C
Hyphen form: 40-04-0C
MAC range: 40:04:0C:00:00:00 – 40:04:0C:FF:FF:FF
Addresses in block: 16,777,216
Organization: A&T
Address: #411, Will Town, 402-3 Bucheon-Si Gyeonggi-Do KR 420-814
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 "A&T"
archived source →
2026-07-17Assigned to "A&T"

Nearby in the registry

The prefixes assigned immediately before and after 40:04:0C:

FAQ

Which company owns MAC address prefix 40:04:0C?: MAC address prefix 40:04:0C is registered to A&T in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 40:04:0C has a network interface built by A&T.
What is the OUI 40:04:0C?: 40:04:0C is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to A&T. It covers every address from 40:04:0C:00:00:00 to 40:04:0C:FF:FF:FF, or 16,777,216 addresses in total. It is also written 40-04-0C.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 40:04:0C:00:00:00 that is 40:04:0C — 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 A&T located?: A&T is listed at #411, Will Town, 402-3 Bucheon-Si Gyeonggi-Do KR 420-814 in the IEEE OUI registry entry for 40:04:0C. This is the address the organization registered with the IEEE, which may differ from its current operating address.