Date: Thu, 25 Mar 1999 23:32:25 -0800 From: bmah@CA.Sandia.GOV (Bruce A. Mah) To: Nick <nick@namodn.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Cable modem: Firewall & Ip Aliasing Message-ID: <199903260732.XAA28795@stennis.ca.sandia.gov> In-Reply-To: Your message of "Thu, 25 Mar 1999 19:29:41 GMT." <Pine.BSF.3.96.990325190353.15727A-100000@namodn.com>
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--==_Exmh_672222227P
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If memory serves me right, Nick wrote:
> I'm trying to set up a LAN which is connected to the internet via cable
> modem. I am doing this by setting up one computer (lets call it wolf) as a
> firewall/gateway for my workstation (lets cann it yeaben)
OK. I have a setup like this at home, except that my "inside" machines are
dual boot Win95/FreeBSD instead of SuSE.
> Ok so im setting wolf up as the FIREWALL & want to masquerade the internal
> lan with a net address of 10.x here is my layout
>
> _FreeBSD_ 3.0 _SuSE Linux_ 6.0
> [-WOLF-] A.B.C.D (outside IP address) [-YEABEN-] 10.2.0.2
> | ed1 | eth0
> | |
> | |
> \_________________________[-HUB-]____________/
> |
> |
> [-CABLE MODEM-]
> |
> |
> /
> /
> [-GATEWAY-] A.B.C.1
> |
> [-DNS-] A.1.64.33
Nice ASCII art. It's missing a few details such as what kind of a cable modem
you're using (and the provider might be useful too), but I'm going to assume
it's like the cable network I use, which is TCI@Home (no snickers please). If
this were my system, I'd say it doesn't work because you shouldn't have the
hub plugged into the cable modem. On the cable modem I use, there should be
exactly one computer. My home network looks like this:
(cable network)<-------[cable modem]-----[gateway]
|
[ hub ]
/ \
[machine1] [machine2]
The gateway (analogous to wolf) is a FreeBSD machine with two Ethernet cards,
and runs ipfw and natd. The interface towards the cable modem has the
"outside IP address", and the one towards the hub has a private IP address (as
do the single Ethernet interfaces on machine1 and machine2).
As far as I know, the way you've wired it up will not work because your
gateway machine needs to have separate "inside" and "outside" network
interfaces. I'm not sure how the cable modem would react to being on the same
Ethernet segment with two (as opposed to one) computers.
I think if you buy another Ethernet card for wolf and wire it up like I drew
above, it'll make a little more sense, and the answers to most of your other
questions will fall into place.
Good luck,
Bruce.
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