IBM Corp

Any device whose MAC address begins with 00:21:5E has a network interface built by IBM 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

00:21:5E

Organization

IBM Corp

Address

3039 E Cornwallis Road Research Triangle Park NC US 27709-2195

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.