1.1.4 Structured Troubleshooting Methods
There are several structured troubleshooting methods that can be used to solve computer and network problems. The troubleshooting method used will vary depending on the type of problem and the personal experience of the technician.
A technician may choose one or more of the following methods to solve a problem:
- Bottom-Up – Start with the physical layer and the physical components of the network and move up through the layers of the OSI model until the cause of the problem is identified.
- Top-Down – Start with the end-user applications and move down through the layers of the OSI model until the cause of the problem has been identified.
- Divide-and-Conquer – Start by collecting user experiences of the problem, document the symptoms and then, using that information, make an informed guess as to which OSI layer to start your investigation.
- Follow-the-Path – Discover the traffic path all the way from source to destination. This approach usually complements one of the other approaches.
- Substitution – Physically swap the problematic device or component with a known, working one. If the problem is fixed, then the problem is with the removed item. If the problem remains, then the cause is elsewhere.
- Comparison – Compare specifics such as configurations, software versions, hardware, or other device properties, links, or processes between working and nonworking situations and spot significant differences between them.
- Educated Guess – A less-structured troubleshooting method that uses an educated guess based on the experience of the technician and their ability to solve problems.