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| 2.2 |  | Troubleshooting Approaches |
| 2.2.5 |  | Guidelines for selecting and approach |

When selecting an effective troubleshooting approach to solve a network problem, the problem is usually resolved in a quicker, more cost-effective manner.

Consider the following when selecting an effective troubleshooting approach.

Determine the scope of the problem
A troubleshooting approach is often selected based on its complexity. A bottom-up approach typically works better for complex problems. Using a bottom-up approach for a simple problem may be overkill and inefficient. Typically, if symptoms come from users then a top-down approach is used. If symptoms come from the network, a bottom-up approach will likely be more effective.

Apply previous experiences
If a particular problem has been experienced previously, then the troubleshooter may know of a way to shorten the troubleshooting process. A less experienced troubleshooter will likely implement a bottom-up approach, while a skilled troubleshooter may be able to jump into a problem at a different layer using the divide and conquer approach.

Analyze the symptoms
The more known about a problem, the better the chance that it can be solved. It may be possible to immediately correct a problem simply by analyzing the symptoms.

Example
Two IP routers have been identified in a network that have connectivity, but are not exchanging routing information. Before attempting to solve the problem, a troubleshooting approach needs to be selected. Similar symptoms have been seen previously, which point to a likely protocol issue. Since there is connectivity between the routers, it is not likely to be a problem at the physical or data link layer. Based on this past experience knowledge, it is decided to use the divide and conquer approach, and the troubleshooter begins testing the TCP/IP-related functions at the network layer.