First, turn your router’s firewall back on. I’ll wait while you go do that.
Ok, now you need to check thoroughly for vermin you may have let in when you disabled the firewall. That’s an anti-virus check, AdAware, and Spybot S&D. It’ll take you a while to do that, but no problem, I’ll wait here while you do that.
Back now? Good. Now write down this very firm rule, “I will not connect to the internet without a firewall”, 500 times.
(Lousy penmanship, there.) Anyway, let’s talk about port-forwarding. Why do that? The reason is, to get one port through a firewall. So if you don’t have a firewall, (because you turned the flippin’ thing off because you didn’t know any better), you don’t have anything that needs a port forwarded through. Got that? A forwarded port is sorta like a pet door to let Rover in. When you turned off the firewall, you took the front door off the hinges. NOT a good way to resolve the issue.
Your firewall protects you from ghastlies and ghosties and long-leggity beasties. Every open port on it is a gate they can come through. You need something there on that opened port to staunchly handle expected traffic through it, and repel all others. That would be, for example, your trusty Bittorrent client. It’s listening on one port. Those others you opened? Holes for the beasties to invade through. So whoever gave you that advice, don’t listen to them anymore.
Now, your router. A router, when hooked to your modem, becomes your face to the outer world. Your ISP, and the whole internet, sees the router. THey see nothing else. They don’t know what’s on the other side of that router. They don’t care what’s on the other side of it. They only talk to the router. What happens behind the router is your problem and they dont’ know and won’t help you with it.
What you do on your side of the router, your subnet, is entirely your affair. You want to set up a static IP in your subnet? Fine. You want some static and some dynamic? Fine. You want them all static? Fine. You want to bridge over to token-ring and connect to forty IBM mainframes and a Vax? Fine. Your subnet, your rules, and also your problem. Set it up any way you want. Change it every other Thursday.
You can set all three computers up as static IP’s within your subnet, and leave a couple of dynamic addresses available for DHCP in case a friend wants to temporarily hook up his laptop to your router.
Just don’t let any two devices ever have the same internal IP address. That way lies madness.
You want to open your bittorrent listen port on the router. Just one port, please. Use the IP of your current Bittorrent machine. All should be well. If you later want to use bittorrent on another computer too, just add another rule pointing to the IP addresses of the other. You can even use the same port number, the router will keep it straight. That’s it’s job.
Now since you’re doing your port-forwarding manually, you don’t want UPnP at all. It has nothing to do, and doesn’t work all that well with most routers anyway. So just disable it in your client.