If you’ve not had a chance to use iPerf at some point in your IT travels for testing TCP/IP links between two machines, you should check it out. It’s pretty nifty, and very lightweight. It easily lets you test bandwidth and performance between two machines on a network.

However, if you’re running VMWare ESXi on a machine, it’s hard to test the true throughput from that machine, since you’d have to run iPerf in a VM. Well, I found out the other day that iPerf can run from the maintenance shell of a VMWare box. Yep, just grab the 32-bit “simple installation” binary from the iPerf website, and drop that anywhere on the filesystem you like. Then just run it by its absolute path. (You MAY have to adjust or disable the built-in ESXi firewall. “esxcli network firewall set –enabled false” will do the trick, but beware this takes the firewall COMPLETELY down and leaves it down. YMMV.)

This saved my bacon the other day, when I needed to rule out the health and speed of our network as a contributor to a problem.