Cisco CCNA Routing and Switching ICND2 200-101 Official Cert Guide

Problem Isolation

Troubleshooting requires that you find the root cause of the problem and then fix it. The process to find the root cause begins with problem isolation. Problem isolation moves you from the general ideas about a problem, to a specific idea of what the problem is, as follows:

Before problem isolation: I have no idea, except for some general symptoms.

After problem isolation: I have an idea of what is not working, a comparison to how it should be working, and I know on which devices it should be working differently.

For example, consider Figure 3-1 again, which shows a packet being delivered from PC1 to PC2, and back, in six routing steps. In this case, however, you determine that R2 gets the packet that flows left to right in ...