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I'm trying to understand the IEEE frames. 802.11 frames have four MAC address fields: The source (original creator of the frame), destination (ultimate destination of the frame), transmitter (the last station to transmit it) and receiver (the next immediate receiver of the frame on its way to the destination).

But 802.3 frames only have two MAC address fields: source and destination. Why is that? Why don't stations connected via Ethernet need to know the previous station that sent a frame?

Thanks for any help.

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  • \$\begingroup\$ Not sure, but I would assume it is because 802.11 has options for WIFI repeaters, logically the same network. \$\endgroup\$
    – Passerby
    Apr 7, 2013 at 1:47
  • \$\begingroup\$ I did notice recently that my laptop 'changes MAC address' when it changes WiFi hotspot. The top 3 bytes change and these bytes are identical for all devices on the 'remote' WiFi hotspot. \$\endgroup\$
    – jippie
    Apr 7, 2013 at 9:36

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In classic Ethernet, any kind of repeating or bridging is transparent. There is only one network segment, as far as all the stations are concerned. If packets cross into another network, they acquire a completely new ethernet identity (and so a higher level networking protocol is needed like IP, for global addressing). The old MAC headers are gone, replaced by new headers.

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