Which company owns MAC address prefix 00:26:66?

MAC address prefix 00:26:66 is registered to EFM Networks in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:26:66 has a network interface built by EFM Networks.

What is the OUI 00:26:66?

00:26:66 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to EFM Networks. It covers every address from 00:26:66:00:00:00 to 00:26:66:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-26-66.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:26:66:00:00:00 that is 00:26:66 — 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.

Where is EFM Networks located?

EFM Networks is listed at 6F, Benposra II 1197-1 Bojeong Giheung Gu Yong In Kyunggi do KR 446913 in the IEEE OUI registry entry for 00:26:66. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does EFM Networks own?

EFM Networks holds 8 OUI prefixes in the IEEE registry, of which 00:26:66 is one. A device made by EFM Networks could carry a MAC address from any of them.

EFM Networks

MAC address prefix 00:26:66 is registered to EFM Networks in the IEEE OUI registry. Any device whose MAC address begins with 00:26:66 has a network interface built by EFM 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 00:26:66:00:00:00 to 00:26:66:FF:FF:FF.

OUI prefix: 00:26:66
Hyphen form: 00-26-66
MAC range: 00:26:66:00:00:00 – 00:26:66:FF:FF:FF
Addresses in block: 16,777,216
Organization: EFM Networks
Address: 6F, Benposra II 1197-1 Bojeong Giheung Gu Yong In Kyunggi do KR 446913
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.

Other prefixes from EFM Networks

EFM Networks holds 8 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

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 "EFM Networks"
archived source →
2026-07-17Assigned to "EFM Networks"

Nearby in the registry

The prefixes assigned immediately before and after 00:26:66:

FAQ

Which company owns MAC address prefix 00:26:66?: MAC address prefix 00:26:66 is registered to EFM Networks in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:26:66 has a network interface built by EFM Networks.
What is the OUI 00:26:66?: 00:26:66 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to EFM Networks. It covers every address from 00:26:66:00:00:00 to 00:26:66:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-26-66.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:26:66:00:00:00 that is 00:26:66 — 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.
Where is EFM Networks located?: EFM Networks is listed at 6F, Benposra II 1197-1 Bojeong Giheung Gu Yong In Kyunggi do KR 446913 in the IEEE OUI registry entry for 00:26:66. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does EFM Networks own?: EFM Networks holds 8 OUI prefixes in the IEEE registry, of which 00:26:66 is one. A device made by EFM Networks could carry a MAC address from any of them.