If you are not familar with firewalld and the firewall-cmd, check out our Getting Started article.

The --list-all-zones option can be used to list the zones. Something like this should be returned for each zone.

~]# firewall-cmd --list-all-zones
public
  target: default
  icmp-block-inversion: no
  interfaces:
  sources:
  services: dhcpv6-client mdns ssh
  ports:
  protocols:
  forward: no
  masquerade: no
  forward-ports:
  source-ports:
  icmp-blocks:
  rich rules:

The --add-interface option can be used to bind an interface to a zone. In this example, eth0 is bound to the public zone.

firewall-cmd --zone=public --add-interface eth0 --permanent
firewall-cmd --reload

The --remove-interface option can be used to remove an interface from a zone.

firewall-cmd --zone=public --remove-interface eth0 --permanent
firewall-cmd --reload

The --check-config command can be used to ensure there are no configuration errors.

~]$ firewall-cmd --check-config
success

The --list-interfaces option can be used to display the interfaces a zone is bound to.

~]# firewall-cmd --zone public --list-interfaces
eth0

Or, the --list-all can be used.

~]# firewall-cmd --list-all
public
  target: default
  icmp-block-inversion: no
  interfaces: eth0
  sources:
  services: smtp
  ports:
  protocols:
  masquerade: no
  forward-ports:
  sourceports:
  icmp-blocks:
  rich rules: