A&T

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.

OUI prefix

40:04:0C

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.