Starting with CentOS 7, FirewallD replaces iptables as the default firewall management tool.

FirewallD  is a complete firewall solution that can be controlled with a  command-line utility called firewall-cmd. If you are more comfortable  with the Iptables command line syntax, then you can disable FirewallD  and go back to the classic iptables setup.

This tutorial will show you how to disable the FirewallD service and install iptables.

Prerequisites

Before starting with the tutorial, make sure you are logged in as a user with sudo privileges.

Disable FirewallD

To disable the FirewallD on your CentOS 7 system, follow these steps:

Type the following command to stop the FirewallD service:

sudo systemctl stop firewalld

Disable the FirewallD service to start automatically on system boot:

sudo systemctl disable firewalld

Mask the FirewallD service to prevent it from being started by another services:

sudo systemctl mask --now firewalld

Install and Enable Iptables

Perform the following steps to install Iptables on a CentOS 7 system:

Run the following command to install the iptables-service package from the CentOS repositories:

sudo yum install iptables-services

Once the package is installed start the Iptables service:

sudo systemctl start iptables

Enable the Iptables service to start automatically on system boot:

sudo systemctl enable iptables

Check the iptables service status with:

sudo systemctl status iptables

To check the current iptables rules use the following commands:

sudo iptables -nvL

By default only the SSH port 22 is open. The output should look something like this:

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
 5400 6736K ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            state RELATED,ESTABLISHED
    0     0 ACCEPT     icmp --  *      *       0.0.0.0/0            0.0.0.0/0           
    2   148 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0           
    3   180 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0            state NEW tcp dpt:22
    0     0 REJECT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            reject-with icmp-host-prohibited

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 REJECT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            reject-with icmp-host-prohibited

Chain OUTPUT (policy ACCEPT 4298 packets, 295K bytes)
 pkts bytes target     prot opt in     out     source               destination     

At  this point, you have successfully enabled the iptables service and you  can start building your firewall. The changes will persist after a  reboot.

Conclusion

In this tutorial, you learned how to disable the FirewallD service and install iptables.

If you have any questions or remarks, please leave a comment below.