Information
firewalld.service is a firewall service daemon that provides a dynamic, customizable firewall with a D-Bus interface.
firewalld.service must be active to enforce rules configured through FirewallD. firewalld.service must be enabled to start automatically after a system reboot.
Solution
Run the following commands to unmask, enable, and start firewalld.service :
# systemctl unmask firewalld.service
# systemctl --now enable firewalld.service
Impact:
Enabling and starting firewalld.service activates host-based packet filtering: from that point, incoming traffic is evaluated against the applicable zone and any traffic that is not permitted is blocked. Ensure the services and ports required for the system's role - including remote administration such as SSH - are allowed, or connectivity to the system can be affected.