I don't think Internet Connection Sharing is what you're after. Although that might work, I think the solution could be much simpler. Let me explain...
You use a cable modem, right? And your Internet Service provider doled out that IP address to you, right? They may have assigned you a fixed IP address which you hand-entered into the configuration screen, or the IP address might be a dynamic one that was automatically assigned from a DHCP pool-- the "pool" representing all the computers in your neighborhood.
Here's the situation: The Empeg is like another computer on the local sub-network. And in the case of cable modems, the "local sub-network" is your neighborhood. So if you take it upon yourself to hand-assign the IP address to the Empeg, you're essentially preventing someone else on your sub-network from getting that IP address. And the minute you unplug the Empeg, then the address becomes "free" again, so someone else might use it. Then the next time you plug in your empeg it won't work and you'll have to go chasing for another IP address.
How you handle this depends upon how your cable company doles out IP addresses. If they assigned you a fixed IP address, then you just broke the rules and might get in trouble for what you did: You just claimed another address without paying for it.
If your cable company uses DHCP, then all you need to do is figure out how to configure the Empeg so that it can see your cable company's DHCP server and get its own dynamic IP each time you plug it in. The reason it's not seeing the DHCP server right now is because the DHCP server is on a different subnet. So you need to tell the Empeg what "Gateway" to use. (Does anyone else have any more information on how Chris should set his gateway setting?)
If setting the Gateway doesn't work, then ICS might solve the problem (by allowing your PC to be the Gateway), but I'd avoid it if I could. I have heard of people who've had lots of trouble with their home networks after setting up ICS.
Another option would be to set up one of those SOHO router products. These are basically a little router, NAT Gateway, firewall, and hub, all built into one little box. They allow multiple computers to share a single internet connection (like your single-ip-address connection), essentially doing in a piece of self-contained hardware what the ICS software would be doing. The advantage is that you don't have to mess up your PC's configuration to do it. And if you're not already using a firewall product with your "always-on" cable modem, you should be, so this could be the best option for you. There are many of these on the market made by dozens of different companies, check them out.
And by the way, you started this thread by saying "Off topic", but I don't think this is off topic at all-- this is important stuff for Empeg owners using ethernet.
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Tony Fabris