iperf3: Local Router Speedtest

Objective

To measure the actual network throughput between two devices connected to the same local router using iperf3.

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What is iPerf3?

iPerf3 is a command-line tool for measuring network bandwidth. It works using a client-server model and can test both upload and download speeds across TCP and UDP protocols.

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Requirements

• Two devices connected to the same local network (wired or wireless)

• iperf3 installed on both devices

• Access to a terminal or command prompt

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Installation

Ubuntu/Debian

sudo apt update
sudo apt install iperf3

macOS (Homebrew)

brew install iperf3

Android (Termux)

pkg install iperf3

Windows

Download from: https://iperf.fr/iperf-download.php

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Test Setup

iPerf3 operates with one device as the server and the other as the client.

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Step-by-Step Test

1. Start the Server

On Device A (e.g., your laptop or Raspberry Pi):

iperf3 -s

This will start the iPerf3 server and wait for incoming connections.

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2. Run the Client

On Device B, determine the IP address of Device A, then run:

iperf3 -c <server_ip_address>

Example:

iperf3 -c 192.168.1.10

This runs a default 10-second test from client to server.

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3. Test in Reverse (Optional)

To test bandwidth from server to client:

iperf3 -c 192.168.1.10 -R

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Understanding the Results

• Focus on the Bandwidth column (in Mbits/sec).

• The value represents the actual throughput between the devices.

• Expect variations based on Wi-Fi vs Ethernet, signal strength, and router quality.

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Additional Options

Option	Description
-t <seconds>	Change test duration (default: 10s)
-P <number>	Use multiple parallel connections

Examples:

iperf3 -c 192.168.1.10 -t 30
iperf3 -c 192.168.1.10 -P 4

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Conclusion

iPerf3 is a simple yet effective tool to test the real network speed between two devices on the same local network. It helps identify potential bottlenecks in routers, cables, or wireless connections.