Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am using iperf to test my bandwidth. But I am not getting whether it is showing my upload or download speed. Say, I have two PCs A and B. If I want to test how fast I can download a file to A from B, where should I run the server i.e "iperf -s" ? on A or B ? Thanks in advance.

share|improve this question

Traffic way is from client to server.

From manpage:

To perform an iperf test the user must establish both a server (to discard traffic) and a client (to generate traffic)

share|improve this answer
There's a great gui to Iperf that can be found at – Florent Courtay Feb 10 '11 at 15:11

With the iperf3 you can use the -R option to send the traffic from Server to client.

  -R, Reverse test mode – Server sends, client receives 
share|improve this answer

It's from to.

So if you run the listen daemon on B, and connect via A thats testing the TX performance from A to B, simply do it the other way around to test the connection back.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.