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
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?
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.