iperf3 support?

We have different ISP's for each of our DD's.   Both sides have said they have upgraded the circuit speed to 300mbps with 600mbps burst.   We are only seeing 200mbps on our replications.

I would like to see which side is not giving us the full meal deal.  There are some iperf sites out on the internet, but they are all version 3 of iperf, and don't seem to work with the iperf on the DD.   Anyone know if 1) there are some iperf version 1 sites available with 500mbs connections or 2) if there is a way to run iperf3 on the DD?

On the other side, we don't have any other equipment plugged in to run speed test/etc.   So I am trying to figure out a way to duplicate the test on both sides so I can clearly tell which ISP is not set up correctly.

Dennis