iperf3
Iperf3 is a network performance testing tool widely used by system and network administrators to measure throughput, bandwidth, latency, and connection stability between two hosts. This guide details how to install and use Iperf3 on Linux, including server-client configuration and TCP/UDP testing.
Preparation
Here is the test scenario:
[Server] ←→ [Router/Switch] ←→ [Client]
192.168.167.89 192.168.167.67
Run the following command for each Linux distribution if iperf3 is not installed:
# AlmaLinux
dnf install iperf3 -y
# Ubuntu/Debian
apt-get install iperf3 -y
Upload Test (Client → Server)
Measures the upload speed from client to server.
Run the following command on the iperf server:
iperf3 -s -p 5201
An example of the output is:
Server listening on 5201
Then run the following command on the iperf client:
iperf3 -c 192.168.167.89 -p 5201 -t 30 -i 5
Output example:
Connecting to host 192.168.167.89, port 5201
[ 5] local 192.168.167.67 port 35532 connected to 192.168.167.89 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-5.00 sec 10.3 GBytes 17.7 Gbits/sec 0 3.10 MBytes
[ 5] 5.00-10.00 sec 10.8 GBytes 18.5 Gbits/sec 0 3.10 MBytes
[ 5] 10.00-15.00 sec 10.7 GBytes 18.4 Gbits/sec 0 3.10 MBytes
[ 5] 15.00-20.00 sec 10.2 GBytes 17.5 Gbits/sec 0 3.10 MBytes
[ 5] 20.00-25.00 sec 10.9 GBytes 18.7 Gbits/sec 0 3.10 MBytes
[ 5] 25.00-30.00 sec 10.4 GBytes 17.9 Gbits/sec 0 3.10 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-30.00 sec 63.3 GBytes 18.1 Gbits/sec 0 sender
[ 5] 0.00-30.04 sec 63.3 GBytes 18.1 Gbits/sec receiver
iperf Done.
The explanation of the iperf3 command above is as follows:
-c: connect to server-p: port number-t: test duration (30 seconds)-i: interval report (5 seconds)
Download Test (Server → Client)
Measures the download speed from server to client. In this test, the client will download data from the server, and the server will upload it. Reverse mode (server sends, client receives).
Run the following command on the iperf server:
iperf3 -s -p 5201
Then, run the following command by adding the -R (reverse test, client receives data) parameter to the iperf client:
iperf3 -c 192.168.167.89 -p 5201 -t 30 -i 5 -R
Output example:
Reverse mode, remote host 192.168.167.89 is sending
[ 5] local 192.168.167.67 port 42108 connected to 192.168.167.89 port 5201
[ ID] Interval Transfer Bitrate
[ 5] 0.00-5.00 sec 10.4 GBytes 17.9 Gbits/sec
[ 5] 5.00-10.00 sec 11.1 GBytes 19.0 Gbits/sec
[ 5] 10.00-15.00 sec 11.0 GBytes 18.8 Gbits/sec
[ 5] 15.00-20.00 sec 10.9 GBytes 18.7 Gbits/sec
[ 5] 20.00-25.00 sec 10.9 GBytes 18.7 Gbits/sec
[ 5] 25.00-30.00 sec 11.0 GBytes 18.9 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-30.04 sec 65.2 GBytes 18.7 Gbits/sec 1 sender
[ 5] 0.00-30.00 sec 65.2 GBytes 18.7 Gbits/sec receiver
iperf Done.
Parallel Test
Test with multiple parallel connections.
Run the following command on the iperf server:
iperf3 -s -p 5201
Then run the following command to test 4 parallel tests on the client:
iperf3 -c 192.168.167.89 -p 5201 -t 30 -i 5 -P 4
UDP Test
Run the following command on the iperf server:
iperf3 -s -p 5201
Run the following command on the iperf client side:
iperf3 -c 192.168.167.89 -p 5201 -u -b 100M -t 10
Here is an example of the output:
Connecting to host 192.168.167.89, port 5201
[ 5] local 192.168.167.67 port 37263 connected to 192.168.167.89 port 5201
[ ID] Interval Transfer Bitrate Total Datagrams
[ 5] 0.00-1.00 sec 11.9 MBytes 99.9 Mbits/sec 8626
[ 5] 1.00-2.00 sec 11.9 MBytes 100 Mbits/sec 8633
[ 5] 2.00-3.00 sec 11.9 MBytes 100 Mbits/sec 8632
[ 5] 3.00-4.00 sec 11.9 MBytes 100 Mbits/sec 8633
[ 5] 4.00-5.00 sec 11.9 MBytes 100 Mbits/sec 8632
[ 5] 5.00-6.00 sec 11.9 MBytes 100 Mbits/sec 8633
[ 5] 6.00-7.00 sec 11.9 MBytes 100 Mbits/sec 8633
[ 5] 7.00-8.00 sec 11.9 MBytes 100 Mbits/sec 8632
[ 5] 8.00-9.00 sec 11.9 MBytes 100 Mbits/sec 8633
[ 5] 9.00-10.00 sec 11.9 MBytes 100 Mbits/sec 8632
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams
[ 5] 0.00-10.00 sec 119 MBytes 100 Mbits/sec 0.000 ms 0/86319 (0%) sender
[ 5] 0.00-10.04 sec 119 MBytes 99.6 Mbits/sec 0.010 ms 0/86319 (0%) receiver
iperf Done.
Explanation of the iperf command above:
-u: UDP mode-b: target bandwidth