As we all know that, CentOS / RHEL 7 both are completely systemd based, So We will have to use few systemd related commands to disable firewalld and enable iptables service. 1. Disable Firewalld Service. [root@localhost ~]# systemctl disable firewalld 2. Stop Firewalld Service. [root@localhost ~]# systemctl stop firewalld 3. Install iptables service related packages. [root@localhost ~]# yum -y i..