In this tutorial, we will show you how to configure Iptables firewall on CentOS. For those of you who didn’t know, Iptables is a versatile tool for Linux, serving as a crucial component for network security. It operates by allowing or blocking traffic based on a set of rules, effectively acting as a firewall. In CentOS, iptables are particularly important for safeguarding the system against unauthorized access and attacks.
This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you the step-by-step configure Iptables Firewall on a CentOS server.
Prerequisites
- A server running one of the following operating systems: CentOS or RHEL-based.
- It’s recommended that you use a fresh OS install to prevent any potential issues.
- A network connection or internet access.
- Mention the need for sudo privileges on a CentOS server and a basic understanding of the CLI.
Configuration Iptables Firewall on CentOS
Step 1. Disable FirewallD
CentOS uses FirewallD by default. To use iptables, you must disable FirewallD with the following commands:
sudo systemctl stop firewalld sudo systemctl disable firewalld sudo systemctl mask firewalld
Step 2. Installing iptables on CentOS.
You can use the following procedure to verify that iptables have been installed and view the status of iptables. Open the terminal and type the following command:
iptables -V sudo yum info iptables
If the above message does not appear, you can type the following command to install iptables:
sudo yum install iptables
Start and enable iptables to run on boot:
sudo systemctl start iptables sudo systemctl enable iptables
Verify the service status:
sudo systemctl status iptables
Step 3. Configuring iptables Rules.
- Configuring iptables Rules
Check existing rules with:
sudo iptables -L
Flush current rules:
sudo iptables -F
Set default policies:
sudo iptables -P INPUT DROP sudo iptables -P FORWARD DROP sudo iptables -P OUTPUT ACCEPT
Add basic rules for services like SSH (port 22), HTTP (port 80), and HTTPS (port 443):
sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT sudo iptables -A INPUT -p tcp --dport 80 -j ACCEPT sudo iptables -A INPUT -p tcp --dport 443 -j ACCEPT
- Creating Custom Chains
Create a custom chain:
sudo iptables -N MY_CHAIN
Implement stateful inspection:
sudo iptables -A INPUT -m state --state NEW,ESTABLISHED -j ACCEPT
Set up NAT and port forwarding:
sudo iptables -t nat -A PREROUTING -p tcp --dport 8080 -j REDIRECT --to-port 80
Manage IP blacklists/whitelists:
sudo iptables -A INPUT -s 1.2.3.4 -j DROP sudo iptables -A INPUT -s 5.6.7.8 -j ACCEPT
- Debugging iptables
Inspect rules with verbose output:
sudo iptables -L -v
Log dropped packets:
sudo iptables -A INPUT -j LOG --log-prefix "DROPPED: "
Check iptables status:
sudo systemctl status iptables
Congratulations! You have successfully Configured Firewall. Thanks for using this tutorial for Configuration Iptables Firewall in the CentOS system. For additional help or useful information, we recommend you check the official CentOS website.
