How to Drop or Block Incoming Access From Specific IP Address Using Iptables

Introduction:

Iptables is a powerful tool used to manage the Linux firewall. It is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. One of the most common use cases of iptables is to block incoming access from specific IP addresses.

--append  -A Append to chain
--delete  -D Delete matching rule from chain
--delete  -D Delete rule rulenum (1 = first) from chain	
--insert  -I Insert in chain as rulenum (default 1=first)
--replace -R Replace rule rulenum (1 = first) in chain
--list    -L List the rules in a chain or all chains

--source      -s [!] address[/mask] source specification
--destination -d [!] address[/mask] destination specification                         
--jump        -j target

INPUT = Incoming Access
OUTPUT = Outgoing Access
-I = Insert
-D = Delete
-s = Source Ip Address
-j = Target Action
DROP = Block action

In this guide, we will show you how to drop or block incoming access from a specific IP address using iptables.

See also  How to Setup Squid Proxy Service on CentOS 5.9

Step 1: Check Current Iptables Rules

Before we begin, let’s check the current iptables rules by running the following command:

sudo iptables -L

This will display the current iptables rules.

Step 2: Add a Rule to Block Incoming Access from a Specific IP Address

To block incoming access from a specific IP address, we need to add a new rule to iptables. The rule will drop all incoming traffic from the IP address.

To add the rule, run the following command:

sudo iptables -A INPUT -s 192.168.1.100 -j DROP

In this command, we are adding a new rule to the INPUT chain to drop all traffic from IP address 192.168.1.100.

See also  How to Install “man” Command on CentOS 5.8

Step 3: Save the Rule

To ensure that the new rule persists after a reboot, we need to save the iptables rules.

To save the current iptables rules, run the following command:

sudo sh -c "iptables-save > /etc/iptables.rules"

This command will save the current iptables rules to the file /etc/iptables.rules.

Step 4: Load the Rule on Boot

To ensure that the new rule is loaded on boot, we need to modify the /etc/rc.local file.

Open the file in a text editor:

sudo nano /etc/rc.local

Add the following line to the file before the exit 0 line:

iptables-restore < /etc/iptables.rules

This command will load the saved iptables rules from the file /etc/iptables.rules on boot.

See also  How to Install Iptables on CentOS 5.8

Step 5: Test the Rule

To test the new rule, try to access your server from the blocked IP address. You should not be able to establish a connection.

Commands Mentioned:

  • iptables - tool used to manage the Linux firewall
  • iptables-save - saves the current iptables rules to a file
  • iptables-restore - loads the saved iptables rules from a file

Conclusion:

In this guide, we have shown you how to drop or block incoming access from a specific IP address using iptables. By adding a new rule to iptables, we can drop all traffic from the specified IP address. Remember to save the iptables rules and load them on boot to ensure that the new rule persists after a reboot.

Comments

Leave a Reply

Your email address will not be published. Required fields are marked *