What this means
The IEEE assigned the MA-L block 00071C to AT&T. 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 00:07:1C, it is AT&T hardware.
Frequently Asked Questions
Who owns MAC prefix 00071C?
00071C is registered to AT&T 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. AT&T's block covers 16,777,216 addresses.
What devices use 00071C?
Any network device with a MAC address starting 00:07:1C was manufactured by or for AT&T.