[vox-tech] 2-nics question

[ME]

Dave Margolis said:
> I want to put an ancient laptop to use as a wireless bridge.  My Gamecube
> sits in a room that I can't get ethernet to without a lot of effort.
> I could buy the Linksys _gaming adapter_ or any of several similar
> devices,
> but I figured this would be worthwhile experiment and I can save some
> cash.

I do not know about the gamecube side of things, but if I replace gamecube
with "generic computer" then what you describe is possible.

This may be useful as a resource. http://nocat.net/ This is a group of
people who have been working on making wireless access points out of
cheap/slow hardware. Their purpose is for creating a community-services
and sourced Internet access for others. However, their project can also be
used to helpyou with the filtering/NAT and other parts.

They have also had discussion on their lists for creating wireless routers
(wireless to wireless kinds of "range extenders" for network access.

> Here is what I have:
>
> P-I 100 / 40MB ram / 2GB HD -  Toshiba Laptop
> Slackware 9.1 slim install < 200MB for base install and some networking

That can be a NAT/DHCP box easily enough.

> 1 wired pcmica nic (dhcp server to the gamecube, and perhaps other
> devices if I get a hub or switch) - eth1
> 1 wireless pcmcia nic (dhcp client to my wireless router) - eth0
>
>
> I just installed the OS and everything is working.  The wireless nic is
> talking to the router and the outside world.  I configured the wired card
> as 192.168.1.1 (my _normal_ home network is 192.168.0.0).
>
> Here is where I don't know what to do next.  I've got DHCP installed, but
> I've never configured it before.  Assuming I can get DHCP working through
> that nic, what software do I need or what configuration is required to
> _pass_ the internet through this machine.  I know I'm showing my
> networking ignorance here, but I've always used a hardware router...

This is not clear. If the laptop will be a dhcp server, then you can check
out the free dhcp server from ISC. You configure it to server addresses in
a subnet. (In this case, the subnet to serve would be 192.168.1.0/24)

It is possible to have a single dhcp server on a network and use DHCHP
relay across subnets, but that will raise the bar on education
requirements when compared to a new dhcp server.

Next, you will need to setup some kind of NAT or masquerading of IP
address information. I expect this will be necessary as your commercial
NAT/Masquerading/Router/Wireless unit is probably configured to only NAT
for the private network for which it is subnetted.

Depending upon the NAT/Masquerading/Router/Wireless unit, you may be able
to have the laptop just act a a router (without NAT/Masquerading) but this
will require support on the NAT/Masquerading/Router/Wireless unit for
routing so that it will know where to "route" packets for the new subnet
based on destination address.

One advantage to simple Masquerading/NAT is that it is modular; you only
need to configure the box doing the NAT and do not need support from the
gateway that is used by the box being configured.

> For this part, I'm sure I can
> RTFM, but if anybody can give me a quick 1,2,3 or point me in the
> direction
> of good reading material, that would be great.

There are NAT/Masquerading how to on the linux documentation project site.
These cover setting up NAT/Masq as well as DHCP server setup. These HOWTO
are "the quick 1, 2, 3." Certainly it is possible to have a shorter list
of steps customized on a per user, per requirement  case, but such
documents have little use for the general population. The HowTo are good
generic docs which cover most generic tasks people desire to accomplish.

> The part I'm really unclear on is this:  do I need a crossover cable to
> talk to the Gamecube (or whatever dhcp client)?  If I plug a hub into the
> wired nic, does that require a crossover cable, or a regular one?

Some newer NIC can auto-sense and auto-flip to match the devices to which
they are connected. (If the device is a hub, then connection is "normal"
while connections directly to other devices can cause the NIC to switch Rx
and Tx to also have that work.)

> I haven't bought the gamecube network adapter yet, and I wasn't planning
> on doing so until I proved this would work (I can always test with another
> laptop).

I do not know about the gamecube side of things, but I know what you
describe is possible for other devices. I have setup my laptop as a
wireless to wired-network router back when wireless was new and some
people wanted network access shared.