How to Use iPerf3 to Test Network Bandwidth

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iPerf3 is an open-source benchmarking tool used to measure the speed of data transfers over a network, ensuring everything works efficiently. iPerf3 tests both the upload and download speeds to provide a complete picture of your network’s performance.

This guide will explain how to download, install, and use iPerf3 on Windows and Linux systems. For optimal operations, we recommend that you run iPerf3 tests when fewer people are using the network due to its high bandwidth usage, which may limit the speed of others.

#Instructions to Use iPerf3 on Windows

#Step 1: Download iPerf3

Visit the iPerf3 download page.
Download the ".zip" file for Windows.

#Step 2: Extract the “.Zip” File

Navigate to your "Downloads" folder.
Right-click the downloaded ".zip" file (e.g., iperf-3.1.3-win64.zip or iperf3.17_64.zip) and select "Extract All..."
Choose a destination folder for the extracted files. You can do this wherever you prefer, but for this tutorial, we will use "C:\Users\cherry\Downloads\iperf3".

#Step 3: Navigate to the iPerf3 directory

Open Command Prompt or PowerShell as an Administrator:
- Command Prompt: Search for "cmd" in the Start menu, right-click Command Prompt, and select "Run as administrator".
- PowerShell: Search for "PowerShell" in the Start menu, right-click Windows PowerShell, and select "Run as administrator".
Use the "cd" command to navigate to the directory where iPerf3 was extracted. Replace "cherry" with your actual username and "x.x" with the version number:
Command Line
```
cd C:\Users\cherry\Downloads\iperf3\iperfx.x_64
```

#Step 4: Run iPerf3

To test the bandwidth, run the following command:
Command Line
```
.\iperf3.exe -c paris.testdebit.info -p 9215 -P 10 
```
Explanation of the flags:
- -c: Specifies the client mode and the server address to connect. In this case, it connects to paris.testdebit.info.
- -p: Specifies the port number to connect to on the server. Here, it uses port 9215.
- -P: Specifies the number of parallel client threads to use. Here, it uses 10 threads.

#Instructions to Use on Linux

#Step 1: Install iPerf3

To install iPerf, simply run the command for your Linux distribution from the list below:
- For Debian/Ubuntu-based systems:
Command Line
```
sudo apt install iperf3
```
- For CentOS/RHEL-based systems:
Command Line
```
sudo yum install iperf3
```
- For Fedora operating systems:
Command Line
```
sudo dnf install iperf3
```
- For Arch Linux-based systems:
Command Line
```
sudo pacman -S iperf3
```
- For openSUSE operating systems:
Command Line
```
sudo zypper install iperf3 
```

#Step 2: Run iPerf3

Run the following command:
Command Line
```
iperf3 -c paris.testdebit.info -p 9215 -P 10 
```
Explanation of the flags:
- -c: Specifies the client mode and the server address to connect. In this case, it connects to paris.testdebit.info.
- -p: Specifies the port number to connect to on the server. Here, it uses port 9215.
- -P: Specifies the number of parallel client threads to use. Here, it uses 10 threads.

#Instructions to Test Network Speed Between Two Servers

To test the speed between two servers using iPerf3, you must set up one server as an iPerf3 server and the other as a client.

#Step 1: Set up the iPerf3 Server

On the first server, start iPerf3 in server mode:
Command Line
```
iperf3 -s
```
This command will start iPerf3 in server mode, listening for incoming connections on the default port - 5201.

#Step 2: Set up the iPerf3 Client

On the second server, run iPerf3 in client mode and connect to the first server. Replace “<server_ip>” with the IP address of the first server:
Command Line
```
iperf3 -c <server_ip>
```

#Step 3: Exit iPerf3 Server Mode

To exit iPerf3 server mode, press Ctrl + C in the terminal where iPerf3 runs.

#Review Test Results

iPerf3 displays the test results in the terminal.

Results show the total bandwidth for both client-to-server and server-to-client directions. An example output of this would be:

Output[ ID] Interval  		Transfer     	Bitrate
[  5] 0.00-10.01 sec  	194 MBytes   162 Mbits/sec    sender
[  5] 0.00-10.05 sec  	193 MBytes   161 Mbits/sec    receiver
[  7] 0.00-10.01 sec 	323 MBytes   270 Mbits/sec    sender
[  7] 0.00-10.05 sec  	322 MBytes   269 Mbits/sec    receiver
[  9] 0.00-10.01 sec  	296 MBytes   248 Mbits/sec    sender
[  9] 0.00-10.05 sec  	293 MBytes   244 Mbits/sec    receiver
[ 11] 0.00-10.01 sec  	580 MBytes   486 Mbits/sec    sender
[ 11] 0.00-10.05 sec  	574 MBytes   479 Mbits/sec    receiver
[ 13] 0.00-10.01 sec  	845 MBytes   708 Mbits/sec    sender
[ 13] 0.00-10.05 sec 	832 MBytes   694 Mbits/sec    receiver
[ 15] 0.00-10.01 sec	1.26 GBytes  1.08 Gbits/sec   sender
[ 15] 0.00-10.05 sec	1.26 GBytes  1.07 Gbits/sec   receiver
[ 17] 0.00-10.01 sec  	235 MBytes   197 Mbits/sec    sender
[ 17] 0.00-10.05 sec  	232 MBytes   194 Mbits/sec    receiver
[ 19] 0.00-10.01 sec  	226 MBytes   189 Mbits/sec    sender
[ 19] 0.00-10.05 sec  	223 MBytes   186 Mbits/sec    receiver
[SUM] 0.00-10.01 sec  3.89 GBytes  3.34 Gbits/sec   sender
[SUM] 0.00-10.05 sec  3.86 GBytes  3.30 Gbits/sec   receiver

iperf Done.

#Additional Resources

List of iPerf3 servers - For a comprehensive list of public iPerf3 servers, visit GitHub iPerf3 Servers.
iPerf3 documentation - Detailed documentation and various test options are available at the iPerf3 Documentation.
iPerf3 server locations - Find a list of servers, their locations, and available ports at iPerf3 Server Locations.

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