Did you ever want to test the network-speed to your ESX-Host with iperf? iperf exists already on installations with vSphere 6.0. Follow this short description:

iperf is located on the ESX host at /usr/lib/vmware/vsan/bin/iperf

Execution of /usr/lib/vmware/vsan/bin/iperf gives an error:

bind failed: Operation not permitted

Workaround: Make a copy of the binary:

cp /usr/lib/vmware/vsan/bin/iperf /usr/lib/vmware/vsan/bin/iperfcopy

Disable the firewall during the tests:

esxcli network firewall set --enabled false

Start the copy of iperf:

/usr/lib/vmware/vsan/bin/iperfcopy -s

Perform tests from client: (download iperf here)

iperf -c <ESX-IP>

After the tests, don't forget to re-enable the firewall with:

esxcli network firewall set --enabled true