I have a 4 port cable router. 3 pc's connected and sharing files, all using internet, etc. All is well, to that point. On one PC,(WinXP), I added a 2nd NIC to network a 4th PC,(Win98). Problem: Can't get file sharing or anything set up. From each PC I can ping the other successfully. That is as far as I can get it. A network search does not find anything about the 2nd NIC PC's. Routers IP, etc. is 192.168.1.100-103, 255.255.255.0. The second NIC on the XP PC, I assigned it 192.168.8.5, 255.255.255.0. The 98 PC I assigned 192.168.8.6, 255.255.255.0.
OK, see the problem is you're going to have to route from one NIC to the other - more complication than is necessary. I'd just buy a hub for upstairs and be done with it. You can probably get one from newegg for $25 or so.
if your handy with a crimper you can do it with just the one wire. assuming your just running 100 base, your one pc is only using two pairs, you can use the other two pairs to connect another computer. ive done it many times, even used the extra pairs to run audio signal through. it was pretty cool if i do say so myself lol.
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