4.8. Troubleshooting Various Network Infrastructures

While there are many ways to build a network, there are really only two main types of network infrastructure in today's networks: wired and wireless. Based on this infrastructure decision, a network administrator or network designer inherits all of the advantages and disadvantages of that type of network. Typically, wireless networks are not completely wireless but actually a wireless infrastructure connected to a wired infrastructure. This means that the network will benefit from all of the advantages of both but will also suffer from all of the disadvantages of both. In this section, we discuss each of these types of network infrastructures and the potential network problems related to each of them.

4.8.1. Critical Information

Given a network troubleshooting scenario involving an infrastructure problem, you should be able to identify the cause of the problem. This requires that you understand the basic design of the two types of network infrastructure: wired and wireless.

4.8.1.1. Wired Infrastructure

As we discussed earlier, most of today's networks are designed in a star topology and a wired infrastructure. This means that each computer has its own network cable that is connected to a central hub or switch. In a large network, that represents a lot of cable. Whether the cable is made of copper or fiber, there is always the possibility that it can become damaged, by being cut or broken. Copper cable can also suffer from electromagnetic interference (EMI) if the cable runs past an electric motor, fluorescent light fixture, or other high-voltage device. These factors can cause communication to fail intermittently or to fail completely, depending on the severity of the problem. Cable lengths that exceed the maximum recommended without the use of a repeater (or hub) can also affect the reliability of computer communication in a network.

Every component in a network including a NIC, hub, switch, router, etc., has a usable "lifetime" before it fails. In addition, every component will most likely fail at some point because it will be used until it fails. Accordingly, most organizations design and manage networks with fault tolerance and redundant components in mind. Their main goal is that if and when a component fails, it can be quickly replaced by a good component and the users can remain productive.

4.8.1.2. Wireless Infrastructure

As we explained earlier, typically a wireless infrastructure is not completely wireless. Most wireless infrastructures are additions to a wired infrastructure and therefore can have the same potential problems as a wired infrastructure. In addition, wireless networks can also suffer from interference from other devices and other radio signals. As we discussed in Chapter 2, most wireless networks use the 2.4GHz wireless radio band. This means that other devices such as wireless telephone, wireless mice, and wireless keyboards can potentially interfere with the communication on these networks. In addition, the structure of the building in which wireless networks are used can affect the reliability of the signal between the computers on the network. As we discussed in Chapter 2, you can use a "trial and error" method to design a functioning wireless network, or you can purchase special programs that determine where signal is traveling throughout your network and at what signal strength.

4.8.2. Exam Essentials

Understand the basic challenges and potential problems with a wired infrastructure, Today's star topology networks use relatively large amounts of cable, since each computer has its own network cable. Copper cables as well as fiber-optic cables can suffer from breaks or cuts. Copper cable connections can suffer from EMI if they are run close to a high-voltage source, such as an electric motor or a fluorescent light. The many components that connect a star topol-ogy (hubs, switches, and routers) have a usable lifetime, which will probably be exceeded before they are taken out of service completely. Therefore, it's not a matter of whether these devices will fail as much as a matter of when they will fail.

Know the basic challenges and potential problems with a wireless infrastructure. Most "wireless" networks are not completely wireless, but instead are a wireless addition to a wired network. Because of this fact, wireless networks can suffer from all of the same problems as wired networks, and then some. You should also understand that wireless networks can suffer from interference due to other devices on the same (or close to the same) frequency. The structure of a building can affect the communication of computers in a wireless network.