What this means
The IEEE assigned the MA-L block 642677 to BKM-Micronic Richtfunkanlagen 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 64:26:77, it is BKM-Micronic Richtfunkanlagen GmbH hardware.