The purpose of Firewalld is to replace the need for iptables and improve the management of security by enabling configuration changes without stopping the current connections. Firewalld runs as a daemon that allows for rules to be added and changed instantly and it uses network zones to define a level of trust for any and all associated network connections. For the troubleshooter, this does provide a range of flexible options but, more importantly, it is necessary to understand that, while a connection can only be a part of a single zone, a zone can be used across many network connections.

To know whether Firewalld is currently running, you can type:

# firewall-cmd --state

To list the predefined zones, you can use:

# firewall-cmd --get-zones