Bi directional test or how efficient is your Ethernet Duplexing:-

zodiac@gml-admin:~$ iperf -c 192.168.0.210 -d
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Client connecting to 192.168.0.210, TCP port 5001
TCP window size: 16.0 KByte (default)
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[ 3] local 192.168.0.17 port 55554 connected with 192.168.0.210 port 5001
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Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
[ 5] local 192.168.0.17 port 5001 connected with 192.168.0.210 port 41681
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.1 sec 9.38 MBytes 7.78 Mbits/sec
[ 5] 0.0-10.3 sec 114 MBytes 92.8 Mbits/sec