Which company owns MAC address prefix 6C:81:66?

MAC address prefix 6C:81:66 is registered to Private in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 6C:81:66 has a network interface built by Private.

What is the OUI 6C:81:66?

6C:81:66 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Private. It covers every address from 6C:81:66:00:00:00 to 6C:81:66:FF:FF:FF, or 16,777,216 addresses in total. It is also written 6C-81-66.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 6C:81:66:00:00:00 that is 6C:81:66 — 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.

Private

MAC address prefix 6C:81:66 is registered to Private in the IEEE OUI registry. Any device whose MAC address begins with 6C:81:66 has a network interface built by Private. 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 6C:81:66:00:00:00 to 6C:81:66:FF:FF:FF.

OUI prefix: 6C:81:66
Hyphen form: 6C-81-66
MAC range: 6C:81:66:00:00:00 – 6C:81:66:FF:FF:FF
Addresses in block: 16,777,216
Organization: Private
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.

2026-01-08Assigned to "Private"
archived source →
2026-07-17Assigned to "Private"

Nearby in the registry

The prefixes assigned immediately before and after 6C:81:66:

FAQ

Which company owns MAC address prefix 6C:81:66?: MAC address prefix 6C:81:66 is registered to Private in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 6C:81:66 has a network interface built by Private.
What is the OUI 6C:81:66?: 6C:81:66 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Private. It covers every address from 6C:81:66:00:00:00 to 6C:81:66:FF:FF:FF, or 16,777,216 addresses in total. It is also written 6C-81-66.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 6C:81:66:00:00:00 that is 6C:81:66 — 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.