I need to test network throughput of a server to/from itself (it's a lonnnng story!).

I love Iperf and use it across the network, but, I just can't figure out how to bind it to a single interface and only listen via that.

From the documentation, I would assume that this would work: iperf -B eth0 -s to bind one instance to eth0, then in another session: iperf -B eth1 -c ip.of.eth.1.

This doesn't work at all, and actually fails. If I use the ip instead of interface, it does work, but, throughput is at 29Gb/s - so, unless there is some magic going on where by I have a super server with a 30Gb/s card, I am guessing that I am not even touching the network and this is just going locally.

Can anyone help me here, or know of a better test/tool?