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I have a screenshot of an ethernet packet frame from Wireshark.

I need to explain what is the meaning of these marked lines (with dots and zeros). I searched in web, but still I don't have an answer.

enter image description here

Thanks!

  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 13 '17 at 5:47
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Both the LG bit (sometimes also referred to as UL bit) and the IG bit are located in the most significant byte of each MAC address, where the IG bit is the least significant bit in this byte and the LG bit is the second least significant bit in this byte.

The IG bit distinguishes whether the MAC address is an individual or group (hence IG) address. In other words, an IG bit of 0 indicates that this is a unicast MAC address, an IG bit of 1 indicates a multicast or broadcast address.

The LG or UL bit on the other hand distinguishes vendor assigned and administratively assigned MAC addresses. When you administratively change the MAC address of your device to another address, then you should set this bit to one. Many drivers and cards however do not enforce this, and I do not know one application which really relies on this one.

So the vast majority of cases (except for broadcast messages) you will see both bits set to 0 (unicast and vendor assigned), as can be confirmed in your screenshot.

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