Question: Examining Hub and Switch Indicator Lights and Uplink Ports Time Required: 30 minutes Objective: Examine the indicator lights of a hub or switch and understand the purpose of the uplink port. Required Tools and Equipment: Three lab computers, four patch cables, one crossover cable, two hubs, and a switch Description: In this project, you view the indicator lights of hubs and switches. Ideally, your hub has indicators for link status, activity, and collisions. In addition, if your hub has an uplink port, you test its function. Like the previous two projects, this project can be done in groups or as a class demonstration
1. The computers should be shut down and one hub should be plugged in and turned on, if necessary. Connect all three computers to the hub with patch cables, but don't use the uplink port on the hub. Turn on the computers.
2. Examine the hub's indicator lights. A link status light should be glowing for each port a computer is connected to. Next, examine the indicator lights on the NIC, if they're accessible. They should also be glowing to indicate a good connection. See whether the hub's indicator lights vary for different connection speeds. Write the link status light's color and the connection speed, if available, in the following chart:
3. Generate some traffic by using ping commands on each computer. At each computer, open a command prompt window and ping another computer (Computer1 ping Computer2, Computer2 ping Computer3, and Computer3 ping Computer1, for example) by typing ping -n 20 IPaddress and pressing Enter. Examine the activity indicator lights, which should blink as data is received. (On hubs combining the activity indicator with the link status, network activity just causes the link status indicator to blink.) The -n 20 option in the ping command specifies sending 20 ICMP packets instead of just 4.
4. Next, if your hub has collision indicators, try to get them to glow. Note that the pings must be sent from each computer at the same time for a collision to occur. At each computer, type ping -n 20 -l 60000 IPaddress and press Enter. The -l 60000 (lowercase "L") option makes each ping packet 60,000 bytes in length. Even with these large amounts of data being transferred, you might not see a collision. Remember that a collision occurs when two or more computers send data simultaneously, which isn't permitted when using a hub. However, if your hub and NICs are operating at 100 Mbps, data is transferred so quickly that producing a collision might be difficult.
5. Leave the first hub powered on, and power on the second hub. With a regular patch cable, connect the first hub to the second hub, but don't use the uplink port. In most cases, you won't see the link lights glow at the ports where the two devices are connected. To fix this problem, plug one end of the patch cable into the uplink port on one hub (not on both hubs) and set the switch to the uplink position. You should now have connectivity between the hubs, and the link lights should be on.
6. If your hubs don't have an uplink port, you can connect two hubs with a crossover cable. To do this, disconnect the two hubs, and using a crossover cable from your instructor, connect each end of it to regular (not uplink) ports on the two hubs. The link lights should glow. (You learn more about patch and crossover cables in Chapter 4.)
7. List any other indicator lights you find on the hub and what these lights tell you:
8. Disconnect the computers from the hubs and put the hubs away. Connect the computers to the switch, and then power on the switch.
9. Along with link status lights, most switches have lights on each port to indicate whether the port is operating in full-duplex or half-duplex mode. If your switch has these indicators, find them and try to determine in which mode your NIC and switch are communicating. Most NICs and switches support full-duplex communication, and this mode is chosen automatically.
10. List any other indicator lights you find on the switch, and explain what these lights tell you:
11. Close all open windows, and shut down the computers.