rsh <ip-src> netperf -H <ip-tgt> -- -S 256000 -s 256000 Where ip-src and ip-tgt were all separate machines (20 machines total) none of which were the head node. I saw wire speed on them all (> 900 Mbit/second), usually close to 940 Mbit/second. So perhaps 10 GB/s switch (minimum), at least in this configuration. This was only a 10 second test... Your milage may vary...