• Check if firewalld is installed: Before enabling the firewall, ensure that the firewalld package is installed on your system. You can check this by running the following command in the terminal:

  rpm -q firewalld

  If firewalld is installed, you'll see its version information. If it's not installed, you can install it using the package manager (yum or dnf).

• Start the firewalld service: If firewalld is installed but not running, you need to start the service. Use the following command to start the firewalld service:

  sudo systemctl start firewalld

• Enable the firewalld service to start on boot: To ensure that firewalld starts automatically at system boot, enable the service using the following command:

  sudo systemctl enable firewalld

• Check the status of firewalld: You can verify that firewalld is running and enabled by checking its status:

  sudo systemctl status firewalld

  This command will show you whether firewalld is active (running) and whether it's set to start automatically at boot.

Once you've completed these steps, the firewall provided by firewalld should be enabled on your RHEL system. You can then proceed to configure firewall rules based on your specific requirements using tools like firewall-cmd or graphical utilities like firewall-config.