Software⏱️ 3 min read📅 2026-06-11

How to Fix: Why am I getting this pf error, “No ALTQ support in the kernel”, in macOS?

macOS pf firewall configuration issue with ALTQ support

Quick Answer: ALTQ is a kernel module that requires macOS to be compiled with ALTQ support, which is not enabled by default.

📋 Table of Contents

  1. ⚠️ Common Causes
  2. ✅ Best Solutions to Fix It
  3. ✨ Wrapping Up

The pf error 'No ALTQ support in the kernel' occurs when you attempt to configure and use the pf firewall on macOS, which is based on the BSD pf system. This issue affects users who want to utilize the pf firewall for its advanced features and flexibility.

This error can be frustrating because it prevents you from fully utilizing the pf firewall's capabilities. However, this guide aims to help you troubleshoot and resolve the issue by exploring possible causes and providing viable solutions.

⚠️ Common Causes

  • The primary cause of this error is that the macOS kernel does not support ALTQ (Advanced Traffic Shaping and Classification), a queueing program used for statistical multiplexing of packets at the kernel level. This is likely due to the fact that macOS uses a different kernel module for packet queuing, which is incompatible with ALTQ.
  • An alternative cause could be that the pf firewall configuration is not compatible with the current kernel version or that there are other system-level issues preventing ALTQ from functioning correctly.

✅ Best Solutions to Fix It

Enabling ALTQ Support

  1. Step 1: To enable ALTQ support, you need to load the pf altq module using the kextload command. Open a Terminal and type `sudo kextload pf_altq` to load the module.
  2. Step 2: After loading the module, you may need to restart your system or reload the pf firewall configuration to take effect.
  3. Step 3: Verify that ALTQ support is enabled by running the `pfctl -s rules` command again. If you still encounter the error, proceed to the next method.

Workaround using pf's built-in features

  1. Step 1: As an alternative, you can configure and use the pf firewall without ALTQ support by utilizing its built-in features. This may limit your ability to take full advantage of advanced pf configurations.
  2. Step 2: To do this, navigate to System Preferences > Security & Privacy > Firewall, and adjust the settings accordingly. You can also use pf commands directly in the Terminal to configure rules and exceptions.

✨ Wrapping Up

In summary, the 'No ALTQ support in the kernel' error occurs due to compatibility issues between the macOS kernel and the pf altq module. To resolve this issue, you can try enabling ALTQ support by loading the pf altq module or use a workaround by configuring and using the pf firewall's built-in features. If you encounter any further issues, consider seeking additional assistance from Apple Support or the pf community.

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