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