How to configure and use the Firewalld firewall to manage network traffic in Linux?

Firewalld is a dynamic firewall management tool in a number of Linux distributions, such as RHEL, CentOS, and Fedora. Unlike static configurations, it allows you to change rules on the fly without restarting services and dropping active connections, using the concept of security zones.

To get started, you need to make sure that the service is running and added to autostart using the systemctl command. You can check the current status via the firewall-cmd utility, which is the main interface for interacting with the firewall daemon.

All network interfaces and connections are distributed into trust zones, for example, public, home, or drop. Each zone defines the level of trust in traffic coming from certain sources, which simplifies the administration of complex network topologies.

Using zones allows you to flexibly restrict access for internal and external networks, improving the overall security of the server infrastructure without the need to write complex rule chains manually.