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@rhel-centos7-tejas-barot-linux ~]# systemctl mask firewalld

2. Stop Firewalld Service.

[root@rhel-centos7-tejas-barot-linux ~]# systemctl stop firewalld

3. Install iptables service related packages.

[root@rhel-centos7-tejas-barot-linux ~]# yum -y install iptables-services

4. Make sure service starts at boot:

[root@rhel-centos7-tejas-barot-linux ~]# systemctl enable iptables

# If you do not want ip6tables, You can skip following command.

[root@rhel-centos7-tejas-barot-linux ~]# systemctl enable ip6tables

5. Now, Finally Let’s start the iptables services.

[root@rhel-centos7-tejas-barot-linux ~]# systemctl start iptables

# If you do not want ip6tables, You can skip following command.

[root@rhel-centos7-tejas-barot-linux ~]# systemctl start ip6tables

Firewalld Service is now disabled and stop, You can use iptables.