Which company owns MAC address prefix B4:3A:31?

MAC address prefix B4:3A:31 is registered to Silicon Laboratories in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with B4:3A:31 has a network interface built by Silicon Laboratories.

What is the OUI B4:3A:31?

B4:3A:31 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Silicon Laboratories. It covers every address from B4:3A:31:00:00:00 to B4:3A:31:FF:FF:FF, or 16,777,216 addresses in total. It is also written B4-3A-31.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in B4:3A:31:00:00:00 that is B4:3A:31 — 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 Silicon Laboratories located?

Silicon Laboratories is listed at 400 West Cesar Chavez Austin TX US 78701 in the IEEE OUI registry entry for B4:3A:31. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Silicon Laboratories own?

Silicon Laboratories holds 156 OUI prefixes in the IEEE registry, of which B4:3A:31 is one. A device made by Silicon Laboratories could carry a MAC address from any of them.

Silicon Laboratories

MAC address prefix B4:3A:31 is registered to Silicon Laboratories in the IEEE OUI registry. Any device whose MAC address begins with B4:3A:31 has a network interface built by Silicon Laboratories. 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 B4:3A:31:00:00:00 to B4:3A:31:FF:FF:FF.

OUI prefix: B4:3A:31
Hyphen form: B4-3A-31
MAC range: B4:3A:31:00:00:00 – B4:3A:31:FF:FF:FF
Addresses in block: 16,777,216
Organization: Silicon Laboratories
Address: 400 West Cesar Chavez Austin TX US 78701
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 Silicon Laboratories

Silicon Laboratories holds 156 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.

2022-07-11Assigned to "Silicon Laboratories"
archived source →
2026-07-17Assigned to "Silicon Laboratories"

Nearby in the registry

The prefixes assigned immediately before and after B4:3A:31:

FAQ

Which company owns MAC address prefix B4:3A:31?: MAC address prefix B4:3A:31 is registered to Silicon Laboratories in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with B4:3A:31 has a network interface built by Silicon Laboratories.
What is the OUI B4:3A:31?: B4:3A:31 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Silicon Laboratories. It covers every address from B4:3A:31:00:00:00 to B4:3A:31:FF:FF:FF, or 16,777,216 addresses in total. It is also written B4-3A-31.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in B4:3A:31:00:00:00 that is B4:3A:31 — 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 Silicon Laboratories located?: Silicon Laboratories is listed at 400 West Cesar Chavez Austin TX US 78701 in the IEEE OUI registry entry for B4:3A:31. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Silicon Laboratories own?: Silicon Laboratories holds 156 OUI prefixes in the IEEE registry, of which B4:3A:31 is one. A device made by Silicon Laboratories could carry a MAC address from any of them.