Which company owns MAC address prefix 2C:91:EF?

MAC address prefix 2C:91:EF is registered to Golmar Sistemas de Comunicacion SA in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 2C:91:EF has a network interface built by Golmar Sistemas de Comunicacion SA.

What is the OUI 2C:91:EF?

2C:91:EF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Golmar Sistemas de Comunicacion SA. It covers every address from 2C:91:EF:00:00:00 to 2C:91:EF:FF:FF:FF, or 16,777,216 addresses in total. It is also written 2C-91-EF.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 2C:91:EF:00:00:00 that is 2C:91:EF — 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 Golmar Sistemas de Comunicacion SA located?

Golmar Sistemas de Comunicacion SA is listed at Silici 13 Cornella de Llobregat Barcelona ES 08940 in the IEEE OUI registry entry for 2C:91:EF. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Golmar Sistemas de Comunicacion SA

MAC address prefix 2C:91:EF is registered to Golmar Sistemas de Comunicacion SA in the IEEE OUI registry. Any device whose MAC address begins with 2C:91:EF has a network interface built by Golmar Sistemas de Comunicacion SA. 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 2C:91:EF:00:00:00 to 2C:91:EF:FF:FF:FF.

OUI prefix: 2C:91:EF
Hyphen form: 2C-91-EF
MAC range: 2C:91:EF:00:00:00 – 2C:91:EF:FF:FF:FF
Addresses in block: 16,777,216
Organization: Golmar Sistemas de Comunicacion SA
Address: Silici 13 Cornella de Llobregat Barcelona ES 08940
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 (1)

The IEEE registry publishes current state only — this is the change record we've kept since we started tracking it daily.

2026-10-02Assigned to "Golmar Sistemas de Comunicacion SA"

Nearby in the registry

The prefixes assigned immediately before and after 2C:91:EF:

FAQ

Which company owns MAC address prefix 2C:91:EF?: MAC address prefix 2C:91:EF is registered to Golmar Sistemas de Comunicacion SA in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 2C:91:EF has a network interface built by Golmar Sistemas de Comunicacion SA.
What is the OUI 2C:91:EF?: 2C:91:EF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Golmar Sistemas de Comunicacion SA. It covers every address from 2C:91:EF:00:00:00 to 2C:91:EF:FF:FF:FF, or 16,777,216 addresses in total. It is also written 2C-91-EF.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 2C:91:EF:00:00:00 that is 2C:91:EF — 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 Golmar Sistemas de Comunicacion SA located?: Golmar Sistemas de Comunicacion SA is listed at Silici 13 Cornella de Llobregat Barcelona ES 08940 in the IEEE OUI registry entry for 2C:91:EF. This is the address the organization registered with the IEEE, which may differ from its current operating address.