Ethernet Address Format

The MAC address or hardware address is a 48 bits (6 bytes) in hexadecimal format and composed of two sections. The first half is assigned by IEEE to a vendor. This is called Organization Unique Identifier or OUI. The second half is the value assigned by the vendor.
The first byte which is the most significant byte has 8 bits total. The 1st bit is the most significant but the 8th bit is the least significant bit. The 7th bit is the universal/local or U/L bit, and the 8th bit is the individual/group or I/G bit.

If the U/L bit is set to 0, it means that it is vendor assigned and globally unique. If it is set to 1, it is administratively assigned.
If the I/G bit is set to 0, it is a unicast frame. However, if it is set to 1, it is either multicast or broadcast frame.
See figure 01.

ethernet frame

Figure 1


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One Response to Ethernet Address Format

  1. Technocrats says:

    Reblogged this on Technocrats.

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