It may be frustrating to learn yet another firewall (firewalld) in Centos or RHEL 7 . Here is how you can switch back to the favorite IPTABLES.
Stop firewalld and disable it to start at boot time :
systemctl stop firewalld systemctl disable firewalld
Now Initiate and enable Iptables (IP V4 ) and ip6tables ( IPV6):
yum install iptables-service touch /etc/sysconfig/iptables systemctl start iptables systemctl enable iptables touch /etc/sysconfig/ip6tables systemctl start ip6tables systemctl enable ip6tables