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CompTIA Linux+ XK0-005 - 2.3 - Key Firewall Features: Zones

Firewalls play a crucial role in securing computer networks by monitoring and controlling network traffic. As part of the CompTIA Linux+ exam objectives, it is important to understand key firewall features, such as zones. This guide will provide you with an overview of zones and how to implement and configure them in a Linux firewall.

Key Firewall Feature: Zones

Zones are a concept used in some firewall technologies to group network interfaces into logical zones based on their security requirements or trust levels. Each zone typically has a specific set of rules and policies associated with it. Implementing zones allows for fine-grained control over network traffic and helps enforce security policies in a more organized manner.

Here's how you can implement and configure zones in a Linux firewall:

  • Identify the firewall technology: Before working with zones, it's important to determine the firewall technology in use. Different firewall technologies may have varying approaches to implementing zones. For example, firewalld is a common firewall management tool that supports zones.

  • Check the current zone configuration: Use the following command to view the current zone configuration:

    sudo firewall-cmd --get-zones

    This command lists the existing zones defined in the firewall configuration.

  • Define custom zones (if necessary): In some cases, you may need to create custom zones tailored to your network environment. The steps to create custom zones may vary depending on the firewall technology in use. For example, with firewalld, you can use the following command to create a new zone:

    sudo firewall-cmd --permanent --new-zone=custom_zone

    Replace custom_zone with the desired name for the new zone.

  • Assign network interfaces to zones: To associate network interfaces with specific zones, use the following command:

    sudo firewall-cmd --permanent --zone=zone_name --change-interface=interface_name
    • zone_name: Name of the zone to which you want to assign the network interface.
    • interface_name: Name of the network interface you want to assign to the zone.


    sudo firewall-cmd --permanent --zone=public --change-interface=eth0

    This command assigns the network interface eth0 to the public zone.

  • Configure rules and policies for each zone: Once you have defined and assigned zones, you can configure rules and policies specific to each zone. These rules control the traffic flow between zones and define what is allowed or denied. The specific commands and configuration settings depend on the firewall technology you are using. Refer to the documentation of your chosen firewall technology to learn how to configure rules and policies for zones.

  • Reload the firewall configuration: After making changes to the zone configuration and rules, reload the firewall to apply the updates:

    sudo firewall-cmd --reload

    This command reloads the firewall configuration, ensuring that the changes take effect.


Implementing and configuring zones in a Linux firewall provides a way to organize and manage network interfaces based on their security requirements. By following the steps outlined in this guide, you will gain a solid understanding of how to work with zones and enforce fine-grained control over network traffic. Remember to consult the documentation of your chosen firewall technology for detailed instructions and additional configuration options.

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