This is the Basic Operation of Firewalld. The definition of services is set to zones on Firewalld. To enable Firewall, assosiate a zone to a NIC with related commands. [1] To use Firewalld, start it. [root@dlp ~]# systemctl start firewalld [root@dlp ~]# systemctl enable firewalld [2] By default, "public" zone is applied with a NIC and dhcpv6-client and ssh are allowed. When operating with "firewall-cmd" command, if you input the command without "--zone=***" specification, then, configuration is set to the default zone. # display the default zone [root@dlp ~]# firewall-cmd --get-default-zone public # display current settings [root@dlp ~]# firewall-cmd --list-all public (default, active) interfaces: eno16777736 sources: services: dhcpv6-client ssh ports: masquerade: no forward-ports: icmp-blocks: rich rules: # display all zones defined by default [root@dlp ~]# firewall-cmd --list-all-zon...