Iperf3 networking testing Print

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Iperf is an Open source network bandwidth testing application, available on Linux, Windows and Unix. Iperf can be used in two modes, client and server. The server runs on the remote host and listens for connections from the client. The client is where you issue the bandwidth test parameters, and connect to a remote server.

Install Iperf on Ubuntu

You can use apt-get install to install Iperf in Ubuntu.

apt-get install iperf

Start server

To start Iperf in server mode, use the below command.

iperf -s

Start server in daemon mode

Running the server without daemon mode keeps the process running in the terminal. Use the -D switch to run it as a daemon in the background.

iperf -s -D

Connecting to server from client

Iperf needs to run on the local host in client mode, as well as in server mode on the remote host. To connect to the remote host, add it’s IP address after the -c switch.

iperf -c

Bi-directional simultaneous (test the speed both ways at the same time)

Use the -d switch to test in the network bandwidth in both directions. This will perform two tests; one from local host to remote host, and another from the remote host to the local host.

iperf -c -d


Bi-directional  (test the speed both one after another)

Use the -r switch to test in the network bandwidth in both directions. This is similar to -d except the tests will be performed in sequence; first from local host to remote host, and another from the remote host to the local host.

iperf -c -r

Change the window size

The TCP window size can be changed using the -w switch followed by the number of bytes to use. the below example shows a window size of 2KB. This can be used on either the server or the client.

iperf -c -w 2048
 iperf -s -w 2048

Change the port

You must use the same port on both the client and the server for the two processes to communicate with each other. Use the -p switch followed by the port number to use on both the local and remote host.

iperf -c -p 9000
iperf -s -p 9000

Change the test duration

The default test duration of Iperf is 10 seconds. You can override the default with the -t switch followed by the time in seconds the test should last.

iperf -s -t 60

UDP instead of TCP

The default protocol for Iperf to use is TCP. You can change this to UDP with the -u switch. You will need to run both the client and server in UDP mode to perform the tests.

iperf -s -u
iperf -c -u

The result will have an extra metric for the packet loss which should be as low as possible, otherwise the packets will have to be re-transmitted using more bandwidth.

Run multiple threads

Iperf can spawn multiple threads to simultaneously send and receive data. Use the -P switch followed by the number of threads to use.

iperf -c -P 4

Check the version of Iperf

Use the -v switch to see the version of Iperf you have installed.

iperf -v

See the full list of arguments

Use the -h switch to see the full list of arguments supported by Iperf.

iperf -h

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