gateway with one interface

["meekaaku kaaku" <meekaaku@gmail.com>]

hi,

I have a small LAN with about 3 windows machiens, 1 debian server
(etch), and adsl router with 4 ports.
Currently, I am using the router as a gateway (192.168.0.1), and the
debian server is 192.168.0.254. The client machiens are configured to
use 192.168.0.1 as a gateway.

What i need to do is to use the linux server 192.168.0.254 as a
gateway for all the client machines, thereby i can monitor traffic and
gives me more control. But the problem is the debian machine has only
one interface and it is not directly connected to internet. It is also
using the router  as the gateway to internet (just like the other
client machines).

So my question is, can this be done? if so any pointers is
appreciated. I have checked routing/iptables info on the web, but in
all the cases, the linux machine is directly connected to the net and
has two interfaces.


thanks,
meekaaku

ps:
I could do squid as an http proxy, but i need to do for all types of traffic.