Which company owns MAC address prefix 00:0C:3F?

MAC address prefix 00:0C:3F is registered to Cogent Defence & Security Networks, in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:0C:3F has a network interface built by Cogent Defence & Security Networks,.

What is the OUI 00:0C:3F?

00:0C:3F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Cogent Defence & Security Networks,. It covers every address from 00:0C:3F:00:00:00 to 00:0C:3F:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-0C-3F.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:0C:3F:00:00:00 that is 00:0C:3F — 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 Cogent Defence & Security Networks, located?

Cogent Defence & Security Networks, is listed at Meadows Road, Newport, South Wales, GB NP19 4SS in the IEEE OUI registry entry for 00:0C:3F. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Cogent Defence & Security Networks,

MAC address prefix 00:0C:3F is registered to Cogent Defence & Security Networks, in the IEEE OUI registry. Any device whose MAC address begins with 00:0C:3F has a network interface built by Cogent Defence & Security Networks,. 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 00:0C:3F:00:00:00 to 00:0C:3F:FF:FF:FF.

OUI prefix: 00:0C:3F
Hyphen form: 00-0C-3F
MAC range: 00:0C:3F:00:00:00 – 00:0C:3F:FF:FF:FF
Addresses in block: 16,777,216
Organization: Cogent Defence & Security Networks,
Address: Meadows Road, Newport, South Wales, GB NP19 4SS
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 "Cogent Defence & Security Networks,"
archived source →
2026-07-17Assigned to "Cogent Defence & Security Networks,"

Nearby in the registry

The prefixes assigned immediately before and after 00:0C:3F:

FAQ

Which company owns MAC address prefix 00:0C:3F?: MAC address prefix 00:0C:3F is registered to Cogent Defence & Security Networks, in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:0C:3F has a network interface built by Cogent Defence & Security Networks,.
What is the OUI 00:0C:3F?: 00:0C:3F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Cogent Defence & Security Networks,. It covers every address from 00:0C:3F:00:00:00 to 00:0C:3F:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-0C-3F.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:0C:3F:00:00:00 that is 00:0C:3F — 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 Cogent Defence & Security Networks, located?: Cogent Defence & Security Networks, is listed at Meadows Road, Newport, South Wales, GB NP19 4SS in the IEEE OUI registry entry for 00:0C:3F. This is the address the organization registered with the IEEE, which may differ from its current operating address.