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GUESTBOOK

Demonstrate knowledge of troubleshooting targets for connection-oriented and connectionless protocols

Reason to use troubleshooting

• Networks are complex and require thorough troubleshooting.
• Difficult problems require a systematic and logical method.

A systematic model

• Does not always resolve problem quicker.
• Does not have to be required in diagnosing Cisco equipment commands.

Eight step of the Cisco troubleshooting model 

1. Define problem.
   1. Main purpose is to form a specific and concise problem statement that directs the focus of the troubleshooting effort.
2. Gather facts.
   1. Reasons are for isolating:
      1. The possible causes of the failure.
      2. The boundary of the problem.
   2. Types of information
      1. Network baseline info.
      2. The scope of the failure.
      3. Whether the trouble is reproducible.
      4. The timeline of the failure.
      5. Symptoms of the failure.
3. Consider possibilities.
4. Create action plan.
   1. Guidelines:
      1. Make one change at a time.
      2. Make non-service-impacting changes.
      3. Do not create security holes while implementing changes.
      4. Leave an avenue available, in case you need to back out of the changes you made.
   2. This step mimics the the Gathering facts.
5. Implement action plan.
6. Observe results.
7. Iterate process. Benefits:
   1. It allows small steps to be made to resolve a larger network failure.
   2. It allows the troubleshooting process to focus on a problem with more and more detail.
   3. It allows for ineffective changes to be removed.
8. Document facts.

Efficient methods of troubleshooting a network failure

1. Inbound (starting on the far end and working back).
2. Outbound (starting with the immediate equipment and working toward the destination).
3. Partitioning or dividing-by-half (dividing the path by half and isolating the problem that way).

Establishing the failure boundary is important because

1. It focuses on the portion of the network or application that is failing.
2. It focuses on the relevant information.
3. It narrows the possibilities of possible failure.

Gather specific information before considering the possible causes of the failure is to shorten the list of possible failures.