Hubs and Switches

The biggest difference between using coaxial cable and twisted-pair cable is that when you use twisted-pair cable, you also must use a separate device called a hub. Years ago, hubs were expensive devices - expensive enough that most do-it-yourself networkers who were building small networks opted for thinnet cable in order to avoid the expense and hassle of using hubs. Nowadays, the cost of hubs has dropped so much that the advantages of twisted-pair cabling outweigh the hassle and cost of using hubs. With twistedpair cabling, you can more easily add new computers to the network, move computers, find and correct cable problems, and service the computers that you need to remove from the network temporarily.

A switch is simply a more sophisticated type of hub. Because the cost of switches has come down dramatically in the past few years, most new networks are built with switches rather than hubs. If you have an older network that uses hubs and seems to run slowly, you may be able to improve the network's speed by replacing the older hubs with newer switches. For more information, see the sidebar, "Hubs and switches demystified," later in this tutorial.

If you use twisted-pair cabling, you need to know some of the ins and outs of using hubs:

• Because you must run a cable from each computer to the hub or switch, find a central location for the hub or switch to which you can easily route the cables.
• The hub or switch requires electrical power, so make sure that an electrical outlet is handy.
• When you purchase a hub or switch, purchase one with at least twice as many connections as you need. Don't buy a four-port hub or switch if you want to network four computers because when (not if) you add the fifth computer, you have to buy another hub or switch.
• You can connect hubs or switches to one another, as shown in Figure below; this is called daisy-chaining. When you daisy-chain hubs or switches, you connect a cable to a standard port on one of the hubs or switches and the daisy-chain port on the other hub or switch. Be sure to read the instructions that come with the hub or switch to make sure that you daisy-chain them properly.
  
• You can daisy-chain no more than three hubs or switches together. If you have more computers than three hubs can accommodate, don't panic. For a small additional cost, you can purchase hubs that have a BNC connection on the back. Then you can string the hubs together using thinnet cable. The three-hub limit doesn't apply when you use thinnet cable to connect the hubs. You can also get stackable hubs or switches that have high-speed direct connections that enable two or more hubs or switches to be counted as a single hub or switch.
• When you shop for network hubs, you may notice that the expensive ones have network-management features that support something called SNMP. These hubs are called managed hubs. Unless your network is very large and you know what SNMP is, don't bother with the more expensive managed hubs. You'd be paying for a feature that you may never use.
• lFor large networks, you may want to consider using a managed switch. A managed switch allows you to monitor and control various aspects of the switch's operation from a remote computer. The switch can alert you when something goes wrong with the network, and it can keep performance statistics so that you can determine which parts of the network are heavily used and which are not. A managed switch costs two or three times as much as an unmanaged switch, but for larger networks, the benefits of managed switches are well worth the additional cost.