EDIT:

See last post

Update:
Well because the RT2500 chipset doesn't show up as an Airport card, there is no way to have OS X turn it into a DHCP server. So looks like I will be searching for an Airport card, or a card that works nativly.

I'll keep this updated.

Later
Chris

You could buy a wireless router, and hook it up to the internet and to the wired router (see if you can set it up as a switch), that would work. Eg, this drawing:


And with a bit of googling I found this:
http://www.ralinktech.com/ralink/Home/Support/Macintosh.html
I just googled "RT2500 mac" Those drivers should work. I don't know what model you have.

Also, why do you want your mac to be your router?

Hello,
I think you missed the part of my post where I said "Now please don't tell me to just "buy" a wireless router. What I have has all been free (except for the G4)." LOL

The RT2500 chipset "does" connect me VIA wireless, but shows up as an ethernet port and not "airport". This means that the Ralink software controls the card and NOT the G4.

I did notice that in the Sharing panel, the option to select more than one connection to share the internet on. So I have a good feeling that once I have an AirPort card, things will work like I want them to.

I'm wanting the G4 to be a router just to see if I can do it, nothing really more than that. Plus I don't have a wireless router and don't want to purchase one...(yet). I was able to find a Netgear PCI wireless card for dirt cheap on ebay, so I am going to buy that and update this post with my findings.

Chris

Sorry. Well just say that it sure wasn't early in the day for me. Your best bet would be to get an official AirPort card. Then you won't have any compatibility problems.

Sorry but I 've no solution for you because I never succeded to make working an ICS scenario as you successfully did.
May you be so kind to post all your configuration item and values involved, I will appreciate immensely !?
thanks and regards
Giovanna

UPDATE: 07/09/2008

I have successfully created a software base station sharing the internet to both wireless and wired devices with WEP security.

Dropped into the G4 a Belkin PCI wireless card Model #F5D7000, version 2000. Showed up right away as an Airport Express Card.

Plugged in all my premade Cat5e cables as shown below.



Hardware :
G4 Running Tiger 10.4.11
CNet 8 Port Ethernet Switch
Belkin PCI wireless card Model #F5D7000
3Com 10/100 PCI Network Card
Motorola DSL Modem


Now under System Preferences --> Sharing --> Internet
I selected Built in Ethernet for "Share your connection from"
Made a checkmark next to Ethernet Connection 2 and Airport
Click Airport Options, named my network, chose password.

Click on start, and there ya go.


Devices Connected:
Hackintosh Desktop (10.5.2)
MACer 5570Z (Sig - Dual boot, OSX 10.5.2 and Vista)
Gateway Laptop (Windows XP)
iPhone
NFusion Nova FTA Sat Receiver
PS2
Soon to be connected, my HackTV

Whatever you name your network, is what will show up in the wireless browsers of other computers. (instead of, linksys, belkin, netgear ... ect)

So there you have it, putting my G4 to use and packing up my old 802.11b router.

I am currently working on getting this same setup to work with OS X Server 10.4.11, there are a few more steps involved.

Hope this helps

Chris

I agree, with this configuration it works without problems. My question is now if it is possible to replace the Ethernet switch with a wireless router collecting wired and wireless machines. In this way I could eliminate the ethernet cable connecting the G4 to the switch (when replaced by a wireless router).
But I'm afraid this is not allowed by OSX Internet Sharing.

Yes, that works fine.

The main reason I didn't do that was because..

first, what's the point of having the G4 act as a NAT server, if your wireless router can be plugged into the modem? and second, most "internet" ports on wireless are only 10mbs. The ethernet ports are 100mbs, but since all information to and from the server is going through that "internet" port, it becomes a bottleneck of 10mbs. Understand?