Re: Is it possible to control access between clients on same LAN with a firewall?

[Will Brickles <wbricks () yahoo com>]

Using DD-WRT, what comes to mind immediately is to put your devices into separate VLANs and then use iptables to 
restrict traffic between the VLANs.  I don't know how flexible DD-WRT is when it comes to VLANs, but it might be your 
best bet on such a platform.  A configuration guide for VLANs I came across is at 
http://www.dd-wrt.com/phpBB2/viewtopic.php?t=1160 - it sounds as if you are already familiar with iptables.

Using other (much more expensive) platforms, you have other options - for example using private VLANs, protected ports, 
"transparent" firewalls, etc.

 Will Brickles




________________________________
From: William Fitzgerald <wfitzgerald () 4c ucc ie>
To: firewall-wizards () listserv cybertrust com
Sent: Mon, January 25, 2010 9:21:59 AM
Subject: [fw-wiz] Is it possible to control access between clients on same LAN with a firewall?

Dear all,

I was just wondering how people control access amongst machines on the same subnet (LAN) that are protected by the same 
firewall.

In my case, the firewall is a home router (WRT54G) running DD-WRT, so iptables is the firewall there.

Presumably as with all firewalls, once a packet is not being sent to the firewall itself or forwarded through the 
firewall towards another network, the firewall will not protect machines behind the firewall from each other. Perhaps 
as a result of the built-in switch, packets don't get up to layer 3 and so the firewall is oblivious to inter-LAN 
packet traffic.

It would be nice to be able to restrict some LAN clients from talking to each other, perhaps by layer 3 filtering. For 
example, it may make sense to prohibit the network printer from talking to a web server and vice versa.

Is there away to force/make it easier for the firewall to inspect inter-LAN packets. Perhaps examining packets at layer 
2 could capture this.

I understand that one solution would be to install a local firewall on each machine.

This is just a general question, so that I might better understand the area of "inter-LAN" protection.

While it may be possible to have a firewall to not just protect traffic from Internet to LAN and LAN to Internet but 
also LAN to LAN, it may not be a practical thing to do.

Any comments or insights are welcomed.

regards,
Will.
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