[Boondoggle]

I've got an iMac that is sharing it's airport connection with an ethernet attached G3. I can get on the net with the G3, but I cannot access it's IP address from other computers on the airport network. No Pings, nothing. I am guessing that it is on a subnet but I don't know how to access that.

[aaanorton]

The iMac is distributing IPs when it shares the connection. I'm pretty sure this is just how it works. There may be a way of disabling DHCP serving for internet sharing, but I don't know of one.
The BEST solution is simply getting a wireless router. This will solve this problem and others as well. It is a far better way to share the internet. And for 36 bucks, it's definitely the way to go.

[Boondoggle]

I've got a wireless router, and the iMac is getting the internet from it. I'm sharing that connection with th G3 via ethernet and that works fine. The problem is that I want to network with the G3 from other computers on the wireless network. That does not work. DHCP is fine, but the IP address the iMac assigns the G3 is not seen on the airport network.

[car1son]

I don't think you can do that with the stock OS X Internet Sharing. When you use internet sharing on the iMac, OS X uses natd to provide NAT to your G3. Essentially the iMac becomes a router, serving the G3 as a subnet. The G3's IP is shielded from the rest of yoru network (the iMac's IP is used for both machines' internet connections) and there's no way to add port forwarding to the OS X Internet Sharing.

You could possibly turn off OS X internet sharing (disabling natd) and assign your G3 a static IP address on the router's subnet, specify the router and netmask as well, and reach the router directly through routed (using the iMac as a switch rather than a router.) Not sure if that will work automagically or if you'll need to use some Unix route commands in the Terminal.
(Addemdum: Nope, doesn't work automagically.)

[Boondoggle]

Thanks for the help... I had a feeling it was something like that. I think I'll just spring for a Wireless to ethernet bridge and get the other box on the air.