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

[K K <kkadow () gmail com>]

Yes.
The most transparent (to the host) technique is what Cisco calls
"private VLAN", see:
http://en.wikipedia.org/wiki/Private_VLAN

There are other approaches to get the same results, all require either
a firewall with lots of interfaces (real or virtual) or a very smart
switch.

Kevin

On 1/25/10, William Fitzgerald <wfitzgerald () 4c ucc ie> wrote:
> 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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