Maximizing Firewall Protection with firewall-cmd: Best Practices and Tips

    skycentral.co.uk | Maximizing Firewall Protection with firewall-cmd: Best Practices and Tips


    Firewalls are an essential component of network security. They act as a barrier between your internal network and the outside world, helping protect your systems from unauthorized access and potential cyber threats. While there are several firewall solutions available, firewall-cmd is a popular choice for managing firewalls on Linux systems. In this article, we will explore some of the best practices and tips to maximize firewall protection using firewall-cmd.

    Understanding firewall-cmd

    firewall-cmd is a command-line tool designed to configure the Linux kernel’s built-in firewall functionality called Netfilter. It provides an easy-to-use interface to manage firewall rules, zones, services, and ports. It allows administrators to define inbound and outbound traffic rules, set up network zones, and control the system’s overall network security.

    Best Practices for Firewall Protection

    When using firewall-cmd, there are several best practices that can help optimize your firewall protection:

    1. Regularly Update Firewall Rules

    Keeping your firewall rules up to date is crucial for maintaining the security of your network. Regularly review and modify your rules according to your evolving network requirements and security policies. Ensure that unnecessary ports are closed and only essential services are allowed through the firewall. Regular updates will help mitigate potential vulnerabilities and reduce the risk of unauthorized access.

    2. Implement Default Deny Policy

    By default, firewall-cmd follows a “default accept” policy, where all incoming connections are allowed unless specifically denied. However, implementing a “default deny” policy is considered a more secure approach. This means that all incoming connections are denied by default unless explicitly permitted. By adopting this practice, you have greater control over incoming traffic and can better safeguard your network against potential threats.

    3. Use Network Zones

    firewall-cmd supports the concept of network zones, which enables you to group hosts based on their network trust levels. For example, you may have different zones for your internal network, a DMZ (Demilitarized Zone), and the Internet. Each zone can have its own set of firewall rules, allowing you to apply stricter policies for external-facing zones while allowing more permissive rules for trusted internal zones. Properly defining and configuring zones in firewall-cmd can significantly enhance your network security.

    4. Limit Access with Source IP(s)

    To further strengthen your firewall protection, consider limiting access to specific source IP addresses or ranges. By specifying allowed sources, you can restrict incoming connections to known and trusted hosts, reducing the risk of unauthorized access. This practice enhances the security of your network by denying connections originating from unknown or potentially malicious sources.

    5. Enable Logging for Firewall Events

    Enabling logging for firewall events can provide valuable insights into network traffic and potential security threats. By monitoring firewall logs, you can identify suspicious activity, analyze patterns, and take appropriate actions to mitigate any potential risks. Regularly reviewing firewall logs is an essential practice for maintaining the security and integrity of your network.

    Useful Tips for Working with firewall-cmd

    In addition to the best practices mentioned above, here are some useful tips for efficiently working with firewall-cmd:

    1. Check Firewall Status

    Before making any changes to your firewall configuration, it’s important to check its status. Use the command firewall-cmd --state to verify if the firewall is currently active or inactive. This will help you determine whether you need to enable or disable the firewall before making any modifications.

    2. View Active Zones

    To view the currently active network zones defined in your firewall-cmd configuration, use the command firewall-cmd --get-active-zones. This will provide a list of zones that are currently active on your system, helping you understand the current network configuration.

    3. Add or Remove Services

    You can add or remove services from the firewall-cmd configuration to allow or deny access to specific ports. Use the commands firewall-cmd --add-service=SERVICE and firewall-cmd --remove-service=SERVICE to add or remove services accordingly.

    4. Reload Firewall Rules

    After making changes to your firewall configuration, it’s crucial to reload the rules for them to take effect. Use the command firewall-cmd --reload to reload the firewall rules and apply any modifications you have made.

    5. List Rules for a Specific Zone

    To view the firewall rules specific to a particular zone, you can use the command firewall-cmd --zone=ZONE --list-all. Replace “ZONE” with the name of the zone you want to inspect. This command lists all the rules associated with the specified zone, giving you a clear overview of the configured firewall rules.


    Maximizing firewall protection with firewall-cmd requires a proactive approach to network security. By following the best practices mentioned above and using the tips provided, you can strengthen your firewall defenses, reduce the risk of unauthorized access, and enhance the overall security of your network. Regularly review and update your firewall rules, implement a default deny policy, leverage network zones, and enable logging to ensure maximum protection. By harnessing the power of firewall-cmd, you can effectively safeguard your systems from potential cyber threats.