3 network card, how to forbidden communication between two nic

username1 · 07-29-2013, 11:46 AM

Hello,

I have linux (Debian) computer with 3 network adapters.

etho - 192.168.100.1 - local network
eth1 - 192.168.1.1 - internet
eth2 - 192.168.7.1 - wireless router connected to it

So, wireless router is connected to eth2.
I want just to forbidden communication between eth2 and eth0. Because eth0 is local network and eth2 is public where users can connect.

How to do that with iptables?

thanks

Ser Olmy · 07-29-2013, 12:49 PM

Code:

iptables -I FORWARD -i eth2 -o eth0 -j DROP

This will add the rule at the very top of the FORWARD chain in the filter table. Note that it will also catch any responses to connections initiated from the eth0 side.

username1 · 07-29-2013, 05:38 PM

So with that command users from eth2 (192.168.7.0) cannot ping or have access to eth0 (192.168.100.0)? Am i right?

Ser Olmy · 07-29-2013, 06:19 PM

Correct.

The command says "add a rule at the top of the FORWARD chain (-I FORWARD), saying that any packets entering eth2 (-i eth2) bound for eth0 (-o eth0) should be processed by the DROP target (-j DROP)".

The FORWARD chain is for packets not destined for the machine itself. The DROP target does just one thing: it discards the packet.

Ser Olmy · 07-29-2013, 06:19 PM

(duplicate, removed)

username1 · 07-30-2013, 04:08 AM

Thank you for help and explanation.
Regards