Locally administered vs. universal MAC addresses
Read the individual/group and universal/local bits without mistaking a prefix for a device identity.
Two low-order bits carry distinct flags
In the first octet, the least significant bit indicates individual versus group addressing; the next least significant bit indicates universal versus local administration. These flags answer different questions.
First octet 02 = 00000010₂ I/G bit (bit 0): 0 → individual address U/L bit (bit 1): 1 → locally administered First octet 00 = 00000000₂ → individual, universally administered
Local administration changes lookup expectations
A locally administered address may be assigned by software or an administrator and need not map to a manufacturer allocation. A vendor-prefix lookup can therefore return no useful manufacturer even when the address is valid on a network.
Randomization can change over time
Operating systems may use randomized MAC addresses for privacy in some network contexts. Do not use a MAC address as a durable person or device identity without a separate, explicit system design.
Inspect the bits before interpreting the prefix
Normalize separators, parse the first octet, and report group/local flags alongside any registry match. State that the registry result is allocation data, not proof of current manufacturer or ownership.