Hat, what you are trying to do(open all ports to multiple computers) is impossible. And port forwarding in ICS is a really pain in the ass, at least it was the last time I used ICS a few years ago.
I'm going to have to suggest the WRT54GL also, but with the Tomato firmware. It is just as stable as OpenWRT, but less complicated to set up, which I like.
And if you are talking about the original Quake, you don't need to open all the ports to host a server.
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