[lug] cable modem network topology

D. Stimits stimits at idcomm.com
Sat Jul 20 13:39:45 MDT 2002

Jeff wrote:
> I have a very similar situation at home.  I have anywhere from 2-4
> machines on my home lan using only 1 outside ip.  Use ip masq'ing.  Much
> easier and cheaper.

Anyone who ever plays a network based game where it is not a 
direct/active set of port requests and responses will be instantly cut 
off. Masquerade is simply not capable of being a full service connect, I 
do not mind setting up bridging if it will do the job (and it looks like 
it will, some of the recent emails have pointed out more current 
information than what I had). Take my word for it when I say masq will 
not do what I need it to do, that it will not work (it will work for 99% 
of the time, but that 1% makes it worthless).

D. Stimits, stimits @ idcomm.com

> Jeff
> LittleViggy at alum.manhattan.edu wrote:
>>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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