What this means
The IEEE assigned the MA-M block 28B77C5 to GROTHE GmbH. 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 28:B7:7C:5, it is GROTHE GmbH hardware.
Frequently Asked Questions
Who owns MAC prefix 28B77C5?
28B77C5 is registered to GROTHE GmbH in the IEEE MA-M registry.
What does the MA-M registry type mean?
An MA-M assignment covers 28 bits of the address, giving the vendor 1,048,576 device addresses, a quarter of a full MA-L block. GROTHE GmbH's block covers 1,048,576 addresses.
What devices use 28B77C5?
Any network device with a MAC address starting 28:B7:7C:5 was manufactured by or for GROTHE GmbH.