Odd latency/speed problems with two desktops

92blacktt

I recently upgraded to gigabit internet and built a new pfsense machine (i5-4570, 8gb, ssd and intel pro lan card). I am getting 750+mbps internet on all my machines except two desktops. These two desktops are only getting around 100 - 250mbps.

I swapped cables and even took the other machines that are getting full speed and put those machines in their place (same Ethernet jack/cables) and they will still get full 750+mbps. I am not sure how to diagnose this problem.

Any suggestion?

NogBadTheBad

Download iperf on the two good and two bad desktops.

Run iperf ( server mode ) to iperf ( client mode ) record the speed between both good desktops
Run iperf ( server mode ) to iperf ( client mode ) record the speed between a good desktops and bad desktop.
Repeat test 2 but put fixed IP addresses on the devices and connect them directly together.

I'm guessing it's the nics on the bad desktops, test 3 would prove this.