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This chapter is from the book

Foundation Summary

The "Foundation Summary" section of each chapter lists the most important facts from that chapter. Although this section does not list every fact from the chapter that will be on your CCNP exam, a well-prepared CCNP candidate should at a minimum know all the details in each "Foundation Summary" before taking the exam.

Table 6-2 Summary of Troubleshooting Approaches

Troubleshooting Approach

How It Operates

Cases It Is Suitable For



Always starts at the physical layer and works its way up until it finds a faulty layer.

More suited for complex cases.

It is a slow, but solid approach.

When the problem is application (or upper layer) related, this approach can take a long time.


Always starts at the application layer and works its way down until it finds a faulty layer.

More suitable for simpler problems or those that are suspected to be application/user or upper-layer related.

If the problem turns out to be related to lower layers, you have wasted a lot of time and effort at the upper or application layers.


Based on the circumstances (reported issues) and your experience, you might decide to start at any layer and work up or down the OSI stack.

Most suitable when you are experienced and the problem has precise symptoms.

It approaches the layer of the culprit faster than the other approaches.

You need experience to use this approach effectively.

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