How to Install, Configure and Use Firewalld in CentOS and Ubuntu

Firewalld (firewall daemon) is an alternative to the iptables service, for dynamically managing a system’s firewall with support for network (or firewall) zones and provides a D-Bus interface for managing configurations. It’s easy to use and configure, and it’s now the default firewall management tool on RHEL/CentOS, Fedora and several other Linux distributions.