Network+

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Next, check the MDI/MDX port setting on small, workgroup hubs, a potential source of trouble that is often overlooked. This port is used to uplink, for example, to a hub on the network’s backbone. The port setting has to be set to either MDI or MDX, depending on the type of cable used for the hub-to-hub connection. A crossover cable (discussed later in this chapter) requires that the port be set to MDI; a standard network patch cable requires that the port be set to MDX (sometimes labeled MDI-X). You can usually adjust the setting via a regular switch or a DIP (Dual Inline Package) switch. Check the hub’s documentation.


Some hubs just have a port labeled MDX, since the MDI setting is really just another standard port for all intents and purposes. If you connect hubs using a standard patch cable, you must connect the MDX port to a standard port on the backbone hub.

Troubleshooting Steps


In the Network+ troubleshooting model, there are eight steps:


1.    Establish symptoms.


2.    Identify the affected area.


3.    Establish what has changed.


4.    Select the most probable cause.


5.    Implement a solution.


6.    Test the result.


7.    Recognize the potential effects of the solution.


8.    Document the solution.


To facilitate our discussion of the troubleshooting steps, let’s assume that a user has called you, the network administrator, to complain about not being able to connect to the Internet.

Step 1: Establish Symptoms


Obviously, if you can’t identify a problem, you can’t begin to solve it. Typically, you need to ask some questions to begin to clarify exactly what is happening. In our example, we should ask the user the following:

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