Who owns MAC prefix F4B381?

F4B381 is registered to WindowMaster A/S in the IEEE MA-L registry.

What devices use F4B381?

Any network device with a MAC address starting F4:B3:81 was manufactured by or for WindowMaster A/S.

MA-L · OUI prefix

WindowMaster A/S

Any MAC address starting F4:B3:81 is registered to WindowMaster A/S in DK.

OUI prefix	F4B381
Vendor	WindowMaster A/S
Registry	MA-L (24-bit, large block)
Country	DK
Example MAC	F4:B3:81:00:00:00

What this means

The IEEE assigned the MA-L block F4B381 to WindowMaster A/S. Every network interface they manufacture under this block has a MAC address beginning with these digits, followed by a unique per-device identifier. If a device on your network shows a MAC starting F4:B3:81, it is WindowMaster A/S hardware.

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