RWE Effizienz GmbH

Any device whose MAC address begins with 9C:30:66 has a network interface built by RWE Effizienz GmbH. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address.

OUI prefix

9C:30:66

Organization

RWE Effizienz GmbH

Address

Flamingoweg 1 Dortmund NRW DE 44139

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.