This chapter covers the following subjects:
The bottom-up troubleshooting approach
The top-down troubleshooting approach
The divide-and-conquer troubleshooting approach
Selecting a troubleshooting approach
You cannot perform troubleshooting on an ad hoc basis in serious production environments; to effectively solve a problem, you must follow a specific methodology. This chapter presents three main approaches to troubleshooting and describes how to select a suitable troubleshooting approach for the problem at hand. As a troubleshooter, you must take your knowledge and aptitude into account and take the approach you feel is most suitable. With a method to follow, you can solve the problem more quickly and cost effectively than if you approached the problem haphazardly. After you have chosen an approach, do not switch to another one in the midst of the troubleshooting effort. Switching methods often causes confusion, wastes time and effort, and impedes the resolution efforts.
"Do I Know This Already?" Quiz
The purpose of the "Do I Know This Already?" quiz is to help you decide if you really need to read this entire chapter. If you already intend to read the entire chapter, you do not need to answer these questions now.
The 10-question quiz, derived from the major sections in the "Foundation Topics" portion of the chapter, helps you determine how to spend your limited study time.
Table 6-1 outlines the major topics discussed in this chapter and the "Do I Know This Already?" quiz questions that correspond to those topics.
Table 6-1 "Do I Know This Already?" Foundation Topics Section-to-Question Mapping
|
Foundation Topics Section |
Questions Covered in This Section |
|
"The Bottom-Up Troubleshooting Approach" |
2 |
|
"The Top-Down Troubleshooting Approach" |
3 |
|
"The Divide-and-Conquer Troubleshooting Approach" |
3 |
|
"Selecting a Troubleshooting Approach" |
2 |
CAUTION
The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you do not know the answer to a question or are only partially sure of the answer, you should mark this question wrong for purposes of the self-assessment. Giving yourself credit for an answer you correctly guess skews your self-assessment results and might provide you with a false sense of security.
Which of the following is an example of a problem that would take place at the network level of the bottom-up approach to troubleshooting?
An interface malfunctions.
A routing loop occurs.
A router heat sink needs to be replaced.
The duplex setting of a port is incorrectly set.
If you have exhausted the possibility of the problem occurring in all but the final level of the top-down troubleshooting approach, which layer are you concerned with?
Physical
Data link
Transport
Application
Using a divide-and-conquer approach, which layer would you begin with if you isolated the problem to an access list on a router?
Physical
Data link
Network
Transport
The power of the Cisco IOS command set encourages which troubleshooting approach?
Bottom-up
Top-down
Divide-and-conquer
Weighted fair
During the course of a troubleshooting case, you started checking the physical devices first. Which approach have you taken?
Bottom-up
Top-down
Divide-and-conquer
LLQ (Low Latency)
A user has initiated a trouble call, and it seems like a trivial case. Which approach should you most likely take?
Bottom-up
Top-down
Divide-and-conquer
Priority approach
Which one of the following is a problem that would occur at the first level of the top-down troubleshooting approach?
The PortFast setting on a port is incorrectly set to off.
The STP state on an interface is incorrectly set to forward.
A jabbering port is identified.
An FTP client application is found to be corrupt.
Which of the following provides the guidelines for selecting the best troubleshooting approach?
Apply experience, analyze the symptoms, and solve the problem.
Select a troubleshooting approach and determine the scope of the problem.
Determine the scope of the problem, analyze it using your experience, and solve it.
Determine the scope of the problem, apply experience, and analyze the symptoms.
Using the divide-and-conquer troubleshooting approach, you decide to begin troubleshooting a TCP/IP problem at the network layer. You determine that the network layer is working properly. Based on this knowledge, which of the following layers is/are not assumed to be working properly?
Physical layer
Data link layer
Transport layer
Application layer
Which troubleshooting approach is most appropriate to implement if the problem is located at the network interface?
Bottom-up
Top-down
Divide-and-conquer
Class-based weighted
You can find the answers to the "Do I Know This Already?" quiz in Appendix A, "Answers to the 'Do I Know This Already?' Quizzes and 'Q&A' Sections." The suggested choices for your next step are as follows:
8 or less overall score—Read the entire chapter. This includes the "Foundation Topics" and "Foundation Summary" sections, as well as the "Q&A" section.
9 or 10 overall score—If you want more review on these topics, skip to the "Foundation Summary" section and then go to the "Q&A" section. Otherwise, move to the next chapter.