Need help with setting up 4 connected home networks and with names.

Hello!

The first thing I need help with is what the terminology for what I want to create is, since that would make finding information, books and such about it a lot easier
It's kinda hard to find information on something you don't know the correct terms for ^^

Current Layout:
I have a house with 3 apartments, each has their own unique internet lines from different ISP's. (and No, getting them all to split on a bigger line is not an option).

Each apartment has it's own home network with several devices connected to their router. With their router being connected to their respective Modems(provided by their ISP).

The problem:
We want to have one or two computers on their own router to act as a fileserver and lan server for our computers.
So that anyone connected to any of the apartments can access the files on the file server(s).


What would the names for the parts of this network be? Is every apartment's network a subnet or?

And what would be a good solution to solve this problem?

Heres a plan for a solution I was thinking of, but I have no idea if it could work as simply as this?

Just adding a switch/router in between everything and editing some settings to get the routers to communicate together?
I guess thats easier said than done, but is it possible?
And would that be an okay solution to use?

Edit: I'm not able to post clickable links / images yet so heres the address itself:
img844.imageshack.us/img844/7643/networklayout.png

Thanks for the diagram.
If you have a switch in the middle then all 4 apartments need to be on the same network/subnet.

If you have a router in the middle instead of a switch then each apartment will be on a different subnet. I recommend the router approach so you can add security. Depending which router you get you can add access rules so the other 3 apartment networks cannot reach each other. And allow them to only reach devices in your network. For that matter you could restrict them to just the FTP server on port 21 to conduct file transfers and restrict them from the PCs in your network.
You'll need a router with firewall capabilities to do this.

You should use private addresses for all of the networks. For example,
Apt 1: 192.168.1.0 255.255.255.0
Apt 2: 192.168.2.0 255.255.255.0
Apt 3: 192.168.3.0 255.255.255.0
Apt 4: 192.168.4.0 255.255.255.0

That's way overkill for the amount of usable addresses per network (254), but it will work. Any traffic to a public address will get routed by the ISP router and dropped by the central router since it won't have a route to it. And vice versa for traffic going to the FTP server.

Thanks a lot for your answer, I will go for the router approach and I already have a suitable router for doing so I believe. (Linksys WRT54G).
So then it's time to play with some cables and have fun with the RJ-45 connectors :P

Once again thanks for your help, very much appreciated!

I've been thinking about this and the last sentence in my previous post is incorrect. The default gateway of the PC will determine which router your packets go to. That can either be set to the ISP router or to the central router but not both.

If you got into the WRT54G you probably noticed you can set a WAN IP address and a LAN IP address. For the router solution you'd need 4 interfaces to set IP addresses on, but the WRT54G only has 2 available.

To get things up and running today you can use all 4 switchports on the WRT54G. Each one connected to a switchport on the respective ISP router. Then just put everything in the same network.

Router 1's LAN IP could be 192.168.1.1 255.255.255.0
PC's on network 1 should have default gateway of 192.168.1.1
PC1-1: 192.168.1.2
PC1-2: 192.168.1.3
PC1-3: 192.168.1.4

Router 2's LAN IP could be 192.168.1.65 255.255.255.0
PC's on network 2 should have default gateway of 192.168.1.65
PC2-1: 192.168.1.66
PC2-2: 192.168.1.67

Router 3's LAN IP could be 192.168.1.129 255.255.255.0
PC's on network 3 should have default gateway of 192.168.1.129
PC3-1: 192.168.1.130
PC3-2: 192.168.1.131
PC3-3: 192.168.1.132

Router 4's LAN IP could be 192.168.1.193 255.255.255.0
PC's on network 4 should have default gateway of 192.168.1.193
PC4-1: 192.168.1.194
Server4-2: 192.168.1.195
Printer4-3: 192.168.1.196

I give you these addresses as an example so that you can easily subnet them into separate networks in the future if you get a router. Probably need a commercial router instead of Linksys to make it work.