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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My name is Karlo, I work as a Network Engineer. A little about myself. I started as a PC gamer back when I was in high school. PC gaming became my addiction and pushed me to learn more about computers. Slowly got my some certifications and landed an IT Tier 1 Helpdesk job. This job opened the door for me to work to push further on my certifications and going deeper into the IT world. My goal was to get my Cisco CCIE Routing and Switching, but my journey for CCIE has changed due to I always ended up working on non-Cisco network appliances. Therefore, I have to pivot and decided to jump to the dark side and go with Juniper. Hopefully, I would get my JNCIE in the near future. All the entries/post I made are based on my views, opinion and for educational purposes only. If you see some mistakes, feel free to drop some comments. I would appreciate all the helpful comments. Thanks
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One Response to Ethernet Address Format

  1. Technocrats says:

    Reblogged this on Technocrats.

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