Table 1-5 I/G and U/L Bits
Field Meaning
I/G Binary 0 means the address is a unicast; Binary 1 means the address is a multicast or
broadcast.
U/L Binary 0 means the address is vendor assigned; Binary 1 means the address has been
administratively assigned, overriding the vendor-assigned address.
The I/G bit signifies whether the address represents an individual device or a group of devices, and
the U/L bit identifies locally configured addresses. For instance, the Ethernet multicast addresses used
by IP multicast implementations always start with 0x01005E. Hex 01 (the first byte of the address)
converts to binary 00000001, with the most significant bit being 1, confirming the use of the I/G bit.
NOTE Often, when overriding the MAC address to use a local address, the device or device
driver does not enforce the setting of the U/L bit to a value of 1.