This switch (E) displays the client MAC address if known. (In practice, this will only be known when the client is ATE.) This could be useful for distinguishing between clients that share an IP address due to some kind of proxy server, and those that are really from the same PC.
Note that "MAC" stands for "Media Access Control," or physical hardware address, and is represented with a code like 00:0E:0C:50:B2:44
History
2006 January, Shell 949, SYSTAT.LIT 3.0(155): Switch added
