A simple Firewall at Linux

Here I want to share a simple firewall example. This will be a firewall using iptables at Linux. We have to create a file at /usr/bin name firewall. We can do this with the following command.

vi /usr/bin/firewall

Then we will edit the file. The edition are written below:

vi /usr/bin/firewall

#!/bin/bash

iptables -F

# set defaukt policy

iptables -P INPUT ACCEPT

iptables -P OUTPUT ACCEPT

iptables -P FORWARD DROP

# accept WAN interface

iptables -A FORWARD -i eth0 -j ACCEPT

# allow a specific IP

iptables -A FORWARD -i eth1 -s 192.168.100.2/32 -d  0/0 -j ACCEPT

Now We will set execution permission to all type user with the following command.

chmod +x /usr/bin/firewall

Now if we write firewall, just like other unix command, it will start firewall file.

For adding at startup configuration we can write a command at /etc/rc.local

vi /etc/rc.local

/usr/bin/firewall

We can also allow or deny any specified MAC also with the following command:

iptables -A FORWARD -i eth0 -s 192.168.100.2 -m mac –mac-source 00:21:D3:C1:11:17 -d 0/0 -j ACCEPT

We have add to the /usr/bin/firewall file.

Expect to get better advice.