Component ProblemsYou Can t Get There from Here

Component Problems”You Can't Get There from Here

Just as in a large corporate network, you might have a problem with one or more components that make up the network. Network cards go bad, as do hubs and switches (and even individual ports on a hub or switch). Always keep handy the minimal documentation that comes with your computer(s), network card, hub, switch, router, and other devices so that you'll know what the LEDs mean when you start troubleshooting.

For example, most network adapters have two LEDs you can examine. One is called the link LED and the other is used to indicate activity on the network. If both of these LEDs are off, you might have a bad network card. Before you make that assumption, however, try moving the cable that plugs the card into the hub or switch/router to a different port and see whether that makes a difference. Check the LEDs on the hub or switch/router to determine whether they have link or activity LEDs. Try switching the patch cable that runs between the network adapter and the port on the switch. Above all, read the documentation to understand what the LEDs mean for your specific product.

Another thing to think about is that many small hubs or switches have an "uplink" port that allows you to connect the device to another one when you want to expand your small LAN. The pinout for this port is not the same as it is for the other ports. The transmit and receive pins are swapped. If you need to plug a computer into an uplink port, you can usually do so, but there will probably be a small button or switch you need to use to change it from an uplink port to a standard port.

Secure Those Cables!

A common problem with small offices or home offices is that you are not using a structured wiring plan. That is, you just string cables from here to there and plug things in. If you have a twisted-pair network cable lying on the floor near your desk, use tie-wraps, scotch tape, or anything else that you can to make sure that the cable doesn't just lie on the floor where you can roll over it with a chair . Even stepping on a twisted-pair network cable can be enough to cause it to have problems carrying the network signal. Secure those cables so that they aren't mangled by accident .

Note

A friend of mine had a pet rabbit at home that was occasionally let out of the cage. Rabbits, in case you don't know, like to chew on just about anything (my friend no longer has the rabbit). Be sure to keep your network cables (not to mention electrical cords) safe, even from your pets!

If you suspect a problem with the cable, trace it from the network card back to the hub or switch/router to be sure that it hasn't been damaged. Never try to "stretch" a cable or pull too hard on it when you are moving things about. This too can damage the cable and cause it to generate so many errors that the network becomes unavailable to the attached computer.

Firewall Problems

If you have installed a router/switch device between your network and a broadband Internet connection, be sure to read the manual thoroughly and understand how the device should be configured. Many come with default settings, but you need to fill in some information, such as the address of the broadband link, if your service provider gives you a static address. In most cases, the provider will be using DHCP also, so you won't have to make any changes. If you do have to make changes, write them down and keep the information handy for later troubleshooting efforts.

Earlier in this chapter, you read that it's not a good idea to mix computers you use for play with those you use for business on the same network. If you do, you are just asking for trouble. If you play Internet games ”those that allow you to interact with other users playing the same game on the Internet ”you might be instructed to change the port settings on a small switch/router that also functions as a firewall. If you start playing around with opening, disabling, or forwarding ports, keep track of the changes you make. If something stops working after you've made a change, undo the modification and see whether the changes you've made have caused the problem.

Remember that the firewall capabilities of a small switch/router are minimal and are designed to protect you from simple attacks from the Internet. It might be that the default settings are very stringent, and if you end up making changes that relax the firewall settings, you might also be opening a door that can allow bad things into your small LAN.

For more information about how firewalls work and the features that are important, see Chapter 49, "Firewalls."