Before you buy anything, let me explain a little about how sharing a cable internet connection actually works. This will help you to buy the right equipment in the first place.

In essence, you always need a device to connect to the cable modem, and hence to the internet. This device is usually a computer (eg the computer that you've already hooked up to the cable modem), but can also be a specialised piece of hardware. Once connected to the internet, the device then shares its connection with the computers in the home network. The device is said to "route" the internet information to the different computers on the network, and is therefore labelled a "router".

Your task is to set up a router. There are 3 fundamental ways of doing this, as follows:

1. Use the computer that's already connected to the cable modem, and install special software on it to make it become a "router". The advantages of this approach are that it's the cheapest and is not too difficult. The main disadvantage is that the computer which is the "router" must always be switched on in order for the other computers to access the internet.

2. Find an old 486 or Pentium, install software to make it into a "router", hide it in a corner somewhere and forget about it. You can install Windows, Linux, whatever you like on this "router". This is basically the same as the first option, but costs a little more (for the old computer, and for the extra electricity). Its advantage over the first option is that each of the "real" computers can connect to the internet without needing any of the other "real" computers to be switched on. This avoids problems such as, eg, a child having to turn on his/her parent's computer in order to play internet games on his/her own computer - at 3am! (not that I'm speaking from personal experience, ahem)

3. Buy a "hardware router". This is a special piece of hardware that can connect to the cable modem and then share that connection ("route") with the computers in the house. It comes with a built-in hub (hubs are explained below), so all you need to buy is the hardware router and some cables. Its advantages are that it's easy to set up and that each computer can connect independently of one another (see above). Its main disadvantage is that it's expensive - around $350-$400 for a Netgear RT314, which is (deservedly) the most popular hardware router for home use.

So which is the best choice? It depends on your priorities! The first option is cheaper than the second, which is in turn cheaper than the third. The third option is easier than the first or the second. The first option is hopeless if you need each computer to be able to connect independently (ie computer 2 needs to connect when computer 1 is switched off, and vice versa).

For the majority of people, the first option is the best. It's far cheaper than buying a hardware router, and not much more difficult to set up. However, if you need the computers to be able to connect independently, then you should investigate one of the other options. Your choice between those will be guided by cost, and also by interest (it's fun, and very flexible, to set up a Linux computer to act as a router (option 2), whereas a hardware router is pretty boring, truth be told).

Since I believe that the first option is the best for most people, that's what this guide covers. For the second option, you could simply follow this guide, although I suspect you'd be using an illegal copy of Windows to do it - for that and other reasons (stability, flexibility, cost etc) I'd encourage you to investigate using Linux on your old 486/Pentium. This guide does not cover Linux, but if you're interested in that solution, feel free to email me for further advice. For the third option, the instructions that come with the hardware router should be sufficient to see you up and running. If not, use section 4.2 of this guide to set up the computers in the network.

From this point on, the information in this guide describes how to set up the first option above.

The hardware needed

You'll need to buy some network cards, some cabling, and perhaps a hub. The specifics will be determined by which type of network you set up...

What type of network should I set up? There are essentially 2 types of networks you need to be aware of, distinguished by the types of cables they use.

The older, slower type of network uses coaxial cables to connect each computer. This type of network is perfectly adequate for internet sharing, and has the following advantages: (1) it is usually cheaper than UTP networks; (2) it doesn't require a hub for more than 2 users; (3) it is easy to add computers to the network later. On the other hand, coaxial networks have these disadvantages: (1) they're slower than UTP networks (that doesn't matter for internet sharing but may be important if you want to share big files across your home network); (2) if one computer "goes down" then the whole network goes down (note that the computer can be off, and even unplugged from the network, and the rest of the network will still function; so this problem is unlikely to be important in the home network setting); (3) the cables are a bit more unsightly than UTP cables.

The modern type of network uses UTP cables (UTP stands for Unshielded Twisted Pair). These look like big fat telephone cables. The advantages of a UTP network are (1) slightly easier to set up if there's only 2 computers; (2) faster than a coaxial network; (3) more standard nowadays; (4) the cables look better and can be longer (up to a hundred metres - how big's your home?). The only real disadvantage of a UTP network is that if you have more than 2 computers you need to buy a hub, which is expensive.

Here's what the connectors look like on the netword card:

I personally use a coaxial network and it works fine, but these days I would recommend getting a UTP network because it's far more common and therefore easier to buy cables, easier to connect to friend's computers etc.

There are 2 common speeds that home networks run at - 10Mbps and 100Mbps. 10Mbps means 10 million bits per second, which is roughly 1.2 megabytes per second. This is way more than a cable modem can sustain, and is therefore ample for sharing an internet connection. 100Mbps connections are, as you'd expect, 10 times as fast as this. These networks are much better for transferring large files (eg if one of the computers in the network has a CD burner and you want to burn a full CD of backup stuff, it takes 2 minutes instead of 20 to transfer the files across the network). The speed of your home network depends on the speed of your network cards - basically the transfer rate between any 2 computers will be the speed of the slowest network card out of those 2 computers. For example, 2 computers with 10/100Mbps cards will transfer data at 100Mbps, but if one of the computers has a 10Mbps card, the transfer rate will be 10Mbps. Most (all?) network cards that are capable of running at 100Mbps can also run at 10Mbps - hence the designation "10/100Mbps".

Network cards: You'll need to buy 1 network card for each computer in the network. Optus or Telstra have already given you either a network card or a USB ethernet adaptor for the server (that is, the computer that is connected to the cable modem), but you still need to buy another network card for it. So what type of cards should you get? The cable modem is not capable of running at even 10Mbps, so 100Mbps cards will give you no more performance for internet use. So if you're really trying to save money you should get 10Mbps cards, which are 100% as good as 100Mbps cards for the internet; but in just about any other circumstance you should get 10/100Mbps cards since the increase in speed for file transfers is dramatic. The only problem is, if you want to set up a coaxial network, most 10/100Mbps cards don't even have coaxial connectors any more! The most flexible card you can buy is a 10/100Mbps card with both coaxial and UTP connectors, but these cards are hard to find. I would recommend getting 10/100Mbps cards, and if you can find ones with coaxial connectors, get those, but don't worry if you can't. You're looking at about $20-$30 for a standard, PCI, 10/100Mbps card. It's a good idea to use a different brand of network card from the one given to you by Optus/Telstra for your server, since this simplifies network configuration (otherwise you're left with 2 network cards which look identical in Windows, trying to guess which one is which). For those who are interested, the network cards provided by Optus/Telstra are 10/100Mbps cards with UTP ports...

Cabling: What type of cabling you need depends, of course, on what type of network you are setting up. There are 3 scenarios: