Arrange the wires so that they lie flat and line up according to Table 9-2.

Switches are more efficient than hubs, but not just because they are faster. If you really want to know, here’s the actual difference between a hub and a switch: ⻬ In a hub, every packet that arrives at the hub on any of its ports is auto- matically sent out on every other port. The hub has to do this because it doesn’t keep track of which computer is connected to each port. For example, suppose Wally’s computer is connected to port 1 on an 8-port hub, and Ward’s computer is connected to port 5. If Ward’s computer sends a packet of information to Wally’s computer, the hub receives the packet on port 1 and then sends it out on ports 2-8. All the computers connected to the hub get to see the packet so they can determine whether or not the packet was intended for them. ⻬ A switch does keep track of which computer is connected to each port. So if Wally’s computer on port 1 sends a packet to Ward’s computer on port 5, the switch receives the packed on port 1 and then sends the packet out only on port 5. This is not only faster, but also improves the security of the system because other computers aren’t shown packets that aren’t meant for them. Working with hubs and switches You only need to know a few details when working with hubs and switches. Here they are, in no particular order: ⻬ Installing a hub or switch is usually very simple. Just plug in the power cord and then plug in patch cables to connect the network. ⻬ Each port on the hub or switch has an RJ-45 jack and a single LED indica- tor labeled Link that lights up when a connection has been established on the port. If you plug one end of a cable into the port and the other end into a computer or other network device, the Link light should come on. If it doesn’t, something is wrong with the cable, the hub or switch port, or the device on the other end of the cable. ⻬ Each port may also have an LED indicator that flashes to indicate net- work activity. If you stare at a hub or switch for a while, you can find out who uses the network most by noting which activity indicators flash the most. ⻬ The ports may also have a Collision indicator that flashes whenever a packet collision occurs on the port. It’s perfectly acceptable for this light to flash now and then, but if it flashes a lot, you may have a problem with the network. Usually this just means that the network is overloaded and should be segmented with a switch to improve performance. But in some cases, a flashing Collision indicator may be caused by a faulty network node that clogs up the network with bad packets. 118 Part II: Building Your Own Network