MAC Address Structure

MAC Address Structure

Here’s where we get into how Ethernet addressing works. It uses the Media Access Control (MAC) address burned into each and every Ethernet network interface card (NIC). The MAC, or hardware, address is a 48-bit (6-byte)address written in a hexadecimal format. You can see your system's MAC address by typing following command at command prompt:
C\>ipconfig /all

Structur of MAc address 
MAC address is divided in to two parts. The organizationally unique identifier (OUI) is assigned by the IEEE to an organization. It’s composed of 24 bits, or 3 bytes. The organization, in turn, assigns a globally administered address (24 bits, or 3 bytes) that is unique to each and every adapter it manufactures.

Structure of MAC

The high-order bit is the Individual/Group (I/G) bit. It can be either 0 or 1.
0 means that the address is the MAC address of a device (unicast).
1 means that the address represents either a broadcast or multicast address.

The next bit is the global/local bit, or just G/L bit.
0, this bit represents a globally unique address (as by the IEEE). When the bit is a 1, it represents a locally unique address. but i know you are confuse, actually 0 means this address belong to physical NIC.
1 means this address this may to virtual NIC if you are running virtual machine on physical machine.

The low-order 24 bits of an Ethernet address represent a manufacturer-assigned code. This portion commonly starts with 24 0s for the first card made and continues in order until there are 24 1s for the last (2^24 = 16,777,216th) card made.

For example 02-00-4C-4F-4F-50
02-00-4c assigned by IEEE for gigabyte manufacture so all gigabyte adapter have same 24 bit but next(4f-4f-50) 24 bit is assigned and start by gigabyte.

02-00-4c-00-00-01  first MAC address
02-00-4c-ff-ff-ff  last MAC address