Which company owns MAC address prefix B8:38:EF?

MAC address prefix B8:38:EF is registered to ADVA Optical Networking Ltd. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with B8:38:EF has a network interface built by ADVA Optical Networking Ltd..

What is the OUI B8:38:EF?

B8:38:EF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to ADVA Optical Networking Ltd.. It covers every address from B8:38:EF:00:00:00 to B8:38:EF:FF:FF:FF, or 16,777,216 addresses in total. It is also written B8-38-EF.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in B8:38:EF:00:00:00 that is B8:38: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 ADVA Optical Networking Ltd. located?

ADVA Optical Networking Ltd. is listed at ADVAntage House York GB YO30 4RY in the IEEE OUI registry entry for B8:38:EF. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does ADVA Optical Networking Ltd. own?

ADVA Optical Networking Ltd. holds 7 OUI prefixes in the IEEE registry, of which B8:38:EF is one. A device made by ADVA Optical Networking Ltd. could carry a MAC address from any of them.

ADVA Optical Networking Ltd.

MAC address prefix B8:38:EF is registered to ADVA Optical Networking Ltd. in the IEEE OUI registry. Any device whose MAC address begins with B8:38:EF has a network interface built by ADVA Optical Networking Ltd.. 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 B8:38:EF:00:00:00 to B8:38:EF:FF:FF:FF.

OUI prefix: B8:38:EF
Hyphen form: B8-38-EF
MAC range: B8:38:EF:00:00:00 – B8:38:EF:FF:FF:FF
Addresses in block: 16,777,216
Organization: ADVA Optical Networking Ltd.
Address: ADVAntage House York GB YO30 4RY
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 ADVA Optical Networking Ltd.

ADVA Optical Networking Ltd. holds 7 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

Assignment history (1)

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

2026-07-17Assigned to "ADVA Optical Networking Ltd."

Nearby in the registry

The prefixes assigned immediately before and after B8:38:EF:

FAQ

Which company owns MAC address prefix B8:38:EF?: MAC address prefix B8:38:EF is registered to ADVA Optical Networking Ltd. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with B8:38:EF has a network interface built by ADVA Optical Networking Ltd..
What is the OUI B8:38:EF?: B8:38:EF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to ADVA Optical Networking Ltd.. It covers every address from B8:38:EF:00:00:00 to B8:38:EF:FF:FF:FF, or 16,777,216 addresses in total. It is also written B8-38-EF.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in B8:38:EF:00:00:00 that is B8:38: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 ADVA Optical Networking Ltd. located?: ADVA Optical Networking Ltd. is listed at ADVAntage House York GB YO30 4RY in the IEEE OUI registry entry for B8:38:EF. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does ADVA Optical Networking Ltd. own?: ADVA Optical Networking Ltd. holds 7 OUI prefixes in the IEEE registry, of which B8:38:EF is one. A device made by ADVA Optical Networking Ltd. could carry a MAC address from any of them.