What this means
The IEEE assigned the MA-L block B48B19 to Apple, Inc.. 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 B4:8B:19, it is Apple, Inc. hardware.
Frequently Asked Questions
Who owns MAC prefix B48B19?
B48B19 is registered to Apple, Inc. in the IEEE MA-L registry.
What does the MA-L registry type mean?
An MA-L assignment, the IEEE's original OUI format, gives the vendor the first three octets and 16,777,216 device addresses under them. Apple, Inc.'s block covers 16,777,216 addresses.
What devices use B48B19?
Any network device with a MAC address starting B4:8B:19 was manufactured by or for Apple, Inc..