Which company owns MAC address prefix 00:12:91?

MAC address prefix 00:12:91 is registered to KWS Computersysteme GmbH in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:12:91 has a network interface built by KWS Computersysteme GmbH.

What is the OUI 00:12:91?

00:12:91 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to KWS Computersysteme GmbH. It covers every address from 00:12:91:00:00:00 to 00:12:91:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-12-91.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:12:91:00:00:00 that is 00:12:91 — 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 KWS Computersysteme GmbH located?

KWS Computersysteme GmbH is listed at Carl Zeiss Str. 1 Ettlingen BW DE 76275 in the IEEE OUI registry entry for 00:12:91. This is the address the organization registered with the IEEE, which may differ from its current operating address.

KWS Computersysteme GmbH

MAC address prefix 00:12:91 is registered to KWS Computersysteme GmbH in the IEEE OUI registry. Any device whose MAC address begins with 00:12:91 has a network interface built by KWS Computersysteme GmbH. 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 00:12:91:00:00:00 to 00:12:91:FF:FF:FF.

OUI prefix: 00:12:91
Hyphen form: 00-12-91
MAC range: 00:12:91:00:00:00 – 00:12:91:FF:FF:FF
Addresses in block: 16,777,216
Organization: KWS Computersysteme GmbH
Address: Carl Zeiss Str. 1 Ettlingen BW DE 76275
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 "KWS Computersysteme GmbH"
archived source →
2026-07-17Assigned to "KWS Computersysteme GmbH"

Nearby in the registry

The prefixes assigned immediately before and after 00:12:91:

FAQ

Which company owns MAC address prefix 00:12:91?: MAC address prefix 00:12:91 is registered to KWS Computersysteme GmbH in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:12:91 has a network interface built by KWS Computersysteme GmbH.
What is the OUI 00:12:91?: 00:12:91 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to KWS Computersysteme GmbH. It covers every address from 00:12:91:00:00:00 to 00:12:91:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-12-91.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:12:91:00:00:00 that is 00:12:91 — 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 KWS Computersysteme GmbH located?: KWS Computersysteme GmbH is listed at Carl Zeiss Str. 1 Ettlingen BW DE 76275 in the IEEE OUI registry entry for 00:12:91. This is the address the organization registered with the IEEE, which may differ from its current operating address.