On Redhat Enterprise Linux and CentOS 7, the firewall service is changed to firewalld. If you prefer iptables, perform the below steps to change it back.
yum -y install iptables-services
Install your iptables script in /etc/sysconfig.
systemctl mask firewalld
systemctl stop firewalld
systemctl enable iptables
systemctl enable ip6tables
systemctl start iptables
systemctl start ip6tables
