Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

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 use iperf to test bandwidth, if i set large test bandwidth, it gives me "WARNING: did not receive ack of last datagram after 10 tries" and there is no report, i want to know what does this mean?

iperf -c xxx -u -b 100m

share|improve this question
up vote 3 down vote accepted

It could be:

Something is blocking the traffic between your hosts.

You specified UDP on the client command, did you do the same on the server side?

The client connection to the server should generate output indicating it has connected, are you seeing this?

share|improve this answer

With what options did you invoke the iperf server? If it's listening on a TCP socket it won't respond to the UDP datagrams that you're sending.

share|improve this answer

Because you are running . two kinds of server on the machine . on server side you are running for both with iperf -s and iperf -s -u like this because of this

share|improve this answer
You may want to look at cleaning up your answer so it makes more sense. – Drew Khoury Nov 14 '13 at 11:19

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.