Software⏱️ 3 min read📅 2026-06-11

How to Fix: iperf3 error exactly 7 seconds into running the test

iperf3 error receiving unknown control message during test, possible causes and solutions.

Quick Answer: The issue is likely due to a misconfigured or incompatible iperf version on the container. Try updating or reinstalling iperf3 to resolve the problem.

📋 Table of Contents

  1. 🔍 Why This Happens
  2. ✅ Best Solutions to Fix It
  3. 🎯 Final Words

The error 'iperf3: error - received an unknown control message' occurs when the iperf client sends an unexpected control message to the server, causing the test to terminate abruptly. This issue affects users running iperf tests on Linux-based systems, particularly those using containers or virtual machines.

This error can be frustrating for network administrators and testers who rely on iperf to measure bandwidth and assess network performance. Fortunately, there are steps you can take to resolve this issue and ensure your iperf tests run smoothly.

🔍 Why This Happens

  • The primary cause of this error is a mismatch between the version of iperf used by the client and server. Iperf versions prior to 3.6.0 may not support certain control messages, leading to this error. Additionally, issues with network interface configuration or packet filtering can also contribute to this problem.
  • Another possible cause is an incorrect configuration of the iperf client or server, which can result in unexpected control messages being sent. This could be due to a misconfigured firewall rule, a missing or corrupted iperf configuration file, or an incorrect setting on the network interface.

✅ Best Solutions to Fix It

Updating iperf versions

  1. Step 1: Update the iperf version on both the client and server to at least 3.6.0 using the package manager (e.g., apt-get or yum) or by downloading the latest binary from the official iperf website.
  2. Step 2: Verify that the updated versions are installed correctly by running the command 'iperf3 -v' on both the client and server.
  3. Step 3: Restart the iperf service or process to ensure the changes take effect.

Configuring network interface settings

  1. Step 1: Check the network interface configuration on both the client and server to ensure that packet filtering and firewall rules are not restricting iperf traffic.
  2. Step 2: Verify that the IP addresses and port numbers used by iperf match those configured in the network interface settings.
  3. Step 3: Adjust or modify the network interface settings as needed to allow iperf traffic to pass through.

🎯 Final Words

By following these steps, you should be able to resolve the 'iperf3: error - received an unknown control message' issue and ensure your iperf tests run smoothly. Remember to update your iperf versions and configure network interface settings as needed to avoid this problem in the future.

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