RHCSA Rapid Track

The netfilter subsystem allows kernel modules to inspect every packet traversing the system. All incoming, outgoing or forwarded network packets are inspected.

The use of firewalld has simplified management by classifying all network traffic into zones. Each zone has its own list of ports and services. The public zone is set as the default zone.

The firewalld service ships with a number of pre-defined services. They can be listed using the firewall-cmd --get-services command.