I've been asked, "Is there any way to share my internet connection and not get charged by my ISP to have multiple computers online?"... Well, short and sweet, yes it's simple to share your internet connection over a home network of computers, today we'll dive into how to setup your ISP for multiple connections...
First, what you'll need as a bare minimum is a Router for your network... You'll need to decide if you want to have to run wire to each area you wish to have each computer at or if you'll want to allow the computers to connect via a wireless connection (or both!).
Myself, I recommend the wireless approach, as you can have both, or move to having both at all times... What I'd recommend as far as hardware is the Linksys WRT54GL router, which is quite affordable in today's market (hardware wise it's basically identical to the WRT54G v4 that Linksys created years ago, which was quite reliable (unlike the newer WRT54G v5+ which are stripped down hardware wise))... If you'd like to go the route of a WIRED connection, there's always the LINKSYS BEFSR41 (it's likely important to note that the wireless router is just about the same price as the wired and has BOTH network ports AND wireless).
Now, most routers have a built in switch, a switch allows multiple computers to connect and will share the connections between your isp and your computers; here the WRT54GL has a 4 port switch built in, which means that 4 computers can be plugged into it and up to 255 computers can connect to the router altogether (wireless, or wired by adding additional switches should your needs grow).
Now, to connect wirelessly to the router, each computer which wants to connect wirelessly will need a wireless card; this card will "pull" the wireless signal and allow you to communicate with your router (they're nice!).
You have a few options, on a desktop you have the PCI cards which just slide into your computer, on a laptop you have PCMCIA cards which just slide into the slot on your computer. On BOTH types though you have USB ones which just plug into the USB slot on your system (which is easy for those which do not wish to take their computer apart).
If you're going the wired approach, any modern PC or Laptop should have a network port built into it, you'll simply need cabling (Clicky).
Now, we need to install and configure our new hardware...
Installing Network Card:
Installing a network card is simple; place it in its appropriate slot and when prompted to install the drivers, press "cancel" then run the CD which comes with the network card, it should install your drivers and prompt you to reboot and you should be installed.
Installing a router
Well, this is at least the fun part lol... Your router will come with a network cable, you'll want to plug the cable into the "WAN" port of your router and plug the other end into your cable or dsl modem. Now you'll plug another network cable into your computer.
Note: At least for the purposes of the initial configuration of the router (setting up wireless) you'll HAVE to have your router plugged into a computer with a cable. You can use the cable which comes with your router (vs plugging it into your modem, at least for the time being).
From here, you'll want to restart your computer, this is so that your system will check for a dhcp server from your router and get its information. After you've rebooted you'll want to open up your web browser of choice and go to http://192.168.1.1 (this is the default address for the Linksys router anyway; the quick start guide which comes with your particular model will show its default address).
Wireless: Now, you'll want to make some adjustments here for your WIRELESS router so that it's secured so only you can use it. I'm writing these out for a Linksys router, your settings may vary depending on vender.
First, go to the "Wireless" tab and make the following config updates:
-- Wireless Mode: AP
-- Wireless Network Mode: Mixed
-- Wireless Network Name: [enter a name for your router here so you can identify your router]
-- Wireless Channel: Auto
-- Wireless SSID Broadcast: Enable
Wireless: Now, in the Wireless Tab you'll want to click the "Security" link, and make the following adjustments:
-- Wireless Interface: WLAN
-- Security Mode: WPA PSK
-- WPA Algorithms: TKIP
-- WPA Shared Key: [enter a password that only you know]
-- Group Key Renewal: 3600
Both: From here, you'll want to visit the "System" tab, and the "DHCP" link, and make these adjustments:
-- DHCP Server: Enable
-- Starting Address: 50
-- Max DHCP: 205
-- Client Lease Time: 86400
Both: From here, you'll want to visit the "Administration" tab.
-- Router Password: [set your password]
-- UPnP: Enable (once you enable it, then visit the page again and turn on all of the upnp options below the upnp option)
Connecting Wireless Computers
From here you'll open the wireless connection setting on all of the wireless computers, it should be in your tool tray and say that it's found a new wireless network! From here simply double click on the linksys applet (or the Windows Wireless Configuration) then it'll show the list of available access points. You'll want to select the one you setup before in your router configuration. Now you'll simply need to enter in your password and you'll be able to connect!
Some Final Steps & Notes
Now, as soon as you plug your router into your cable modem, and connect your wireless computers, you should be online with all computers.
Should you not be able to connect to the internet, simply go back to your router setup and go to the "Status" tab, under the "Router" link you'll see an "internet configuration" area, all of the options here should have numbers, if for some reason the ip address isn't set, you'll want to click the "DHCP Release" and "DHCP Renew" buttons and test your internet again. If these do not make the router pull an ip address from your ISP you'll need to make sure you're connected from the router to the modem.