Basic Troubleshooting Approach: What Has Changed?

Figure C-1 shows a basic troubleshooting model.

Figure C-1. Troubleshooting Model

NOTE

Remember that during the CCIE Lab Exam that any notes or documentation you make cannot be taken with you when you leave the lab. This model is to help you to create a standard method to troubleshoot problems that will help you to quickly identify problems during your exam.

When analyzing a problem you should consider the flowchart in Figure C-1 and the following facts:

• Make sure you have a clear definition of the problem.

• Gather all the relevant facts and consider the likely possibilities.

• Create and implement an action plan and then observe the results. Before beginning to troubleshoot a problem, ensure that you save a backup copy of the configuration that you can use to fall back to if your action plan does not resolve the problem.

• If the symptoms do not stop, try another action plan and gather additional facts. If you try one thing and it does not work, you should take that configuration or feature off. In case you make the situation worse, always keep it basic and get back to a known position.

• If the symptoms do stop, document how you fixed the problem.

This model can help you to identify and fix network problems, especially network implementation problems. Every fact (or question) that you gather is very important and most of the time will lead you to the primary reason for a failed implementation. When implementing or solving a real problem or during your CCIE Lab Exam, ask yourself the following questions:

• What has changed?

• What was the last change or configuration made?

These questions can quickly identify what is causing or caused your network to stop receiving routes updates or stopped a previously successful ping to a router's interface, and so on.

Because you are implementing a network following a set of sequential requirements, the potential number of ways you have to "break" something during the exam is high. Because of this, you need to have complete control of what is happening and in what you are configuring. Documentation is the key to tracking your progress and identifying problems.