Which company owns MAC address prefix B4:B1:5A?

MAC address prefix B4:B1:5A is registered to Siemens AG Energy Management Division in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with B4:B1:5A has a network interface built by Siemens AG Energy Management Division.

What is the OUI B4:B1:5A?

B4:B1:5A is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Siemens AG Energy Management Division. It covers every address from B4:B1:5A:00:00:00 to B4:B1:5A:FF:FF:FF, or 16,777,216 addresses in total. It is also written B4-B1-5A.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in B4:B1:5A:00:00:00 that is B4:B1:5A — 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 Siemens AG Energy Management Division located?

Siemens AG Energy Management Division is listed at Humboldtstr. 59 Nurnberg Bavaria DE 90459 in the IEEE OUI registry entry for B4:B1:5A. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Siemens AG Energy Management Division

MAC address prefix B4:B1:5A is registered to Siemens AG Energy Management Division in the IEEE OUI registry. Any device whose MAC address begins with B4:B1:5A has a network interface built by Siemens AG Energy Management Division. 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 B4:B1:5A:00:00:00 to B4:B1:5A:FF:FF:FF.

OUI prefix: B4:B1:5A
Hyphen form: B4-B1-5A
MAC range: B4:B1:5A:00:00:00 – B4:B1:5A:FF:FF:FF
Addresses in block: 16,777,216
Organization: Siemens AG Energy Management Division
Address: Humboldtstr. 59 Nurnberg Bavaria DE 90459
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 "Siemens AG Energy Management Division"
archived source →
2026-07-17Assigned to "Siemens AG Energy Management Division"

Nearby in the registry

The prefixes assigned immediately before and after B4:B1:5A:

FAQ

Which company owns MAC address prefix B4:B1:5A?: MAC address prefix B4:B1:5A is registered to Siemens AG Energy Management Division in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with B4:B1:5A has a network interface built by Siemens AG Energy Management Division.
What is the OUI B4:B1:5A?: B4:B1:5A is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Siemens AG Energy Management Division. It covers every address from B4:B1:5A:00:00:00 to B4:B1:5A:FF:FF:FF, or 16,777,216 addresses in total. It is also written B4-B1-5A.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in B4:B1:5A:00:00:00 that is B4:B1:5A — 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 Siemens AG Energy Management Division located?: Siemens AG Energy Management Division is listed at Humboldtstr. 59 Nurnberg Bavaria DE 90459 in the IEEE OUI registry entry for B4:B1:5A. This is the address the organization registered with the IEEE, which may differ from its current operating address.