[lug] cable modem network topology

LittleViggy at alum.manhattan.edu LittleViggy at alum.manhattan.edu
Fri Jul 19 10:53:26 MDT 2002

Why the need for Internet addys for each machine behind the firewall?  Couldn't 
you setup IP masq'ing, and just use one Internet IP?

My setup (albeit DSL) is like this, on Windows (yuck!).  I have one machine 
that has the DSL card and an Ethernet card.  It's running NAT32p (a Windows 
program for doing IP masqing).  From the two machines behind the router 
machine, I can do anything I want (including VPN).  The only thing I cannot do 
is have people contact machines behind my router, which is not a problem for me.

If you could get away with that, it's prolly less of a headache to setup.  And, 
it saves you $10 /mo...  Best of all, the ISP really need not know that you've 
done this!



D. Stimits wrote:
> Within the last two weeks, my telephone line quality went permanently 
> downhill. Not only is it between 25% and 33% slower, latency seems to 
> have doubled. The phone company is not interested until it drops below 
> 14.4kbps. Within roughly the last week, cable modems became available 
> for a good price (especially compared to DSL).
> What I want to do is use an old P166 as the firewall/router/gateway, but 
> it is complicated by the need for 3 IP addresses, all of which are 
> dhcp/non-static. Each dynamic address beyond the first costs $5 each, 
> but that is fine for 3 computers that might run at the same time. The 
> gateway/router/firewall does not need a routable IP as far as I am 
> concerned. What I wanted was something like this:
> cable modem
>     | (eth0)
>   P166 firewall/gate/router
>     | (eth1)
>   8 port switch
>     |
>     |- Machine 1
>     |- Machine 2
>     |- Machine 3
> But how to actually do this is a mystery, it seems as though the P166 
> would need eth0 to respond to multiple dhcp IP's, and then transparently 
> forward them to whichever machine booted up, while still allowing rules 
> to stop things like port 137-139 from passing through. I have never set 
> up a DHCP system, which seems easy if only one machine touches the cable 
> modem, but becomes problematic if the P166 must simply pass through DHCP 
>  packets, then do the right firewalling for each machine. Can this be done?
> D. Stimits, stimits @

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