EXTENSION TECHNOLOGY CORP.

Any device whose MAC address begins with 00:40:7D has a network interface built by EXTENSION TECHNOLOGY CORP.. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address.

OUI prefix

00:40:7D

Organization

EXTENSION TECHNOLOGY CORP.

Address

30 HOLLIS STREET FRAMINGHAM MA US 01701

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.