How To Whitelist An IP Address In IPTables

Details

To whitelist an IP address in IPTables (Linux's firewall management tool), you need to add a rule that allows incoming traffic from the specified IP address while blocking all other incoming traffic. Here's a step-by-step guide on how to do this:

Note: You should have administrative privileges (root or sudo access) to modify the firewall rules.

• Open a Terminal: Access your Linux server or computer and open a terminal window.
• Check Existing Rules (Optional): You can check your existing IPTables rules to ensure that you don't already have a rule that conflicts with the one you're going to add. You can do this with the following command:

sudo iptables -L

This command will list the current rules. Make sure to look under the INPUT chain.

• Add the Whitelist Rule: Allow incoming connections from 192.168.0.1 you can use the following command:

sudo iptables -A INPUT -s 192.168.0.1 -j ACCEPT

This command appends a rule to the INPUT chain that accepts traffic from the specified IP address (192.168.0.1).

• -A: Appends the rule to the end of the chain.
• -s: Specifies the source IP address you want to allow.
• -j ACCEPT: Indicates that traffic from the specified IP should be accepted.
• Add the Whitelist Rule: Allow outgoing connections from 192.168.0.1 you can use the following command:

iptables -A OUTPUT -d 192.168.0.1 -j ACCEPT

This command appends a rule to the INPUT chain that accepts traffic from the specified IP address (192.168.0.1).

• -A: Appends the rule to the end of the chain.
• -d: This option sets the destination IP address for the rule
• -j ACCEPT: Indicates that traffic from the specified IP should be accepted.
• Save the Rules: To ensure your changes persist across reboots, you need to save the IPTables rules. The method for doing this may vary depending on your Linux distribution. For example, on Ubuntu/Debian, you can use:

sudo iptables-save > /etc/iptables/rules.v4

On CentOS/RHEL, you can use:

sudo service iptables save

• Verify the Rule: After adding the rule, it's a good practice to verify that it's in place. You can list the rules again with:

sudo iptables -L

You should see your new rule allowing traffic from the specified IP address.

• Restart IPTables (Optional): In some cases, you might need to restart IPTables or your server for the changes to take effect. You can do this with:

sudo systemctl restart iptables

Now, traffic from the whitelisted IP address (192.168.0.1 in this example) will be allowed through your firewall, while all other incoming traffic will be blocked by default. Make sure to replace 192.168.0.1 with the actual IP address you want to whitelist.

Example