If I have one computer connected to a router and another two computers connected to each other, how do I get one of the other computers that are directly connected to see the computer connected to the router on a network ? tongue twister :)
Why arent you connecting all of the computers to the router directly? If the router doesnt have enough ports, plug in a switch to the router, then plug all of your hosts to the switch. Make sure that all of your computers are on the same logical IP scheme.
It's similar setup rather
Computer 1 <--> Computer 2
Computer 3 <--> Router
What your saying is, if I connect all the computers to the router they will be able to share information amoungst each other, rather then my current setup. If so, where does a switcher come into this solution, if it does at all ?
The switch is not required if your router has enough ports. Most of the consumer based routers come with 4 ports. If your router only has one port, then you need a switch. If your router has wireless capability, then you obviously can leverage that as well to add additional nodes to this network.
Once you plug in your computers into the router, assuming that you have your Windows computers' network cards set to DHCP clients, they will all receive a compatible IP configuration. From there you can work on sharing resources between computers.
Keep in mind that sharing requires correct permissions on files and folders as well as configuring the local firewalls to allow the appropriate traffic.
I dont understand why you are asking why you should only use one NIC port to connect to the network?
Some computers have multiple NICs, but that doesnt mean you need to plug all of them in to the network. If you plug multiple NICs into the same logical subnet, there is not benefit. You are only adding complexitity to the network connection.
Multiple NICs are used when you need to plug the computer into multiple VLANs for specific reasons.