alexachucarro,
Although not actually supported by Apple in 10.1.x (ie there's no simple button to do it), you CAN setup a software basestation network using OS X. I have such a setup at home - an iMac DV and Titanium G4 with airport cards, no base station - ADSL connected to the iMac and then shared between both machines via airport.
The trick is to jump on the sustainable softworks website (don't remember the URL offhand) and download their OS X version of IPNetRouter (which is actually gNAT rebadged). Follow the setup instructions for both machines (host and client) and you'll be right, with a few caveats:
1. If you want to use the internet on the host machine also, you'll have to setup a 'dummy' IP router on the airport interface that sets up the airport IP address (needed for the client machine), and then passes all packets to the cable connection (router the same as your IP address on the cable configuration, 0.0.0.0 as a subnet mask).
2. If using ADSL (not sure about cable) there were issues with the MTU (maximum transport unit - basically the size of the packets being transferred) that emerged with 10.1, and were fixed under 10.1.1. Basically the symptoms of this is that smaller packets (eg pings, or sometimes mail packets) are transferred properly, but larger web packets are not - so you were not able to use the web. However, when using the Airport connection as the primary connection, this problem re-emerges until you apply the temporary (ie needed for each restart of the computer):
in the terminal, type:
sudo ifconfig en1 mtu 1492
(ie reset the mtu size to 1492 bytes for the airport interface).
3. The settings and NAT seem to take a few minutes to propegate, so don't dispair if things don't work right away - give it a few minutes, then try again.
4. If the host goes to sleep, the NAT is broken and thus your internet connection is lost - so be sure to setup the host to stay awake whilst you're on the net. The screensaver on my iMac also seems to upset the connection, but as it SHOULDN'T do that, I wouldn't worry about the possibility straight away.
Hope this helps you,
Cheers,
James Hodge
james.hodge@beatentrack.com.au
http://photo.beatentrack.com.au
