Information
firewall zones define the trust level of network connections or interfaces.
Note: The firewall in the Linux kernel is not able to handle network connections with the name shown by NetworkManager, it can only handle the network interfaces used by the connection. Because of this NetworkManager tells firewalld to assign the network interface that is used for this connection to the zone defined in the configuration of that connection. This assignment happens before the interface is used. The configuration of the connection can either be the NetworkManager configuration or also an ifcfg. For example: If the zone is not set in the configuration file, the interfaces will be assigned to the default zone defined in the firewalld configuration. If a connection has more than one interface, all of them will be supplied to firewalld. Also changes in the names of interfaces will be handled by NetworkManager and supplied to firewalld.
Rationale:
A network interface not assigned to the appropriate zone can allow unexpected or undesired network traffic to be accepted on the interface.
Impact:
Changing firewall settings while connected over network can result in being locked out of the system.
Solution
Run the following command to assign an interface to the approprate zone.
# firewall-cmd --zone=<Zone NAME> --change-interface=<INTERFACE NAME>
Example:
# firewall-cmd --zone=customezone --change-interface=eth0
Default Value:
If the zone is not set in the configuration file, the interfaces will be assigned to the default zone defined in the firewalld configuration