Why do we need sender MAC address in ARP request?
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[Here][1] is a wireshark capture of an ARP request PNG image, I contains the sender MAC inside the ARP packet. The receiving station can derive the MAC from the Ethernet frame. It seems to be redundant. Is there any particular use of separately including the sender MAC address in ARP Request too ?.

  [1]: http://wiki.wireshark.org/AddressResolutionProtocol?action=AttachFile&do=get&target=arp.png