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iptables

Creating a firewall using iptables

I need to create a file to filter traffic.

It should work like this:

  • Input traffic from 192.168.5.0/24 should be blocked unless it's ICMP or from 192.168.5.200
  • Output traffic to 192.168.5.0/24 should be blocked unless it's ICMP or to 192.168.5.200
  • The remaining traffic should be allowed.

This is my solution:

iptables -P INPUT DROP
iptables -F INPUT
iptables -A INPUT -i eth0 -p ICMP -s 192.168.5.200 -j ACCEPT
iptables -A INPUT -i eth0 -s 192.168.5.0 -j DROP
iptables -A OUTPUT -o eth0 -p ICMP -d 192.168.5.200 -j ACCEPT
iptables -A OUTPUT -o eth0 -d 192.168.5.0 -j DROP
iptables -A OUTPUT ACCEPT
iptables -A INPUT ACCEPT

I'm new to iptables, so I appreciate any help I can get.

Solution

  • Try rules like this:

    iptables -P INPUT ACCEPT
iptables -A INPUT -s 192.168.5.200 -j ACCEPT
iptables -A INPUT -s 192.168.5.0/24 -p icmp -j ACCEPT
iptables -A INPUT -s 192.168.5.0/24 -j DROP
iptables -P OUTPUT ACCEPT
iptables -A OUTPUT -d 192.168.5.200 -j ACCEPT
iptables -A OUTPUT -d 192.168.5.0/24 -p icmp -j ACCEPT
iptables -A OUTPUT -d 192.168.5.0/24 -j DROP