Objectives
Upon completion of this chapter, you will be able to answer the following questions:
- What are some of the approaches used to troubleshoot networks?
- What is the process of detecting physical layer problems?
- How do you troubleshoot a wireless network problem?
- What are the common Internet connectivity problems?
- What outside sources and Internet resources are available for troubleshooting?
Diego has completed her task of designing and setting up a new branch network. He will need to test it, and if there are problems, she will diagnose and fix them. I want to know how to test, diagnose, and fix network problems too. Being able to do this is a sure sign that you are ready to become a networking professional.
Let’s do this together!
The Troubleshooting Process (36.1)
Troubleshooting is the process of identifying, locating, and correcting problems. Experienced individuals often rely on instinct to troubleshoot. However, there are structured techniques that can be used to determine the most probable cause and solution.
Video—Network Troubleshooting (36.1.1)
Refer to the online course to view this video.
Network Troubleshooting Overview (36.1.2)
When troubleshooting, proper documentation must be maintained. This documentation should include as much information as possible about the following:
- The problem encountered
- Steps taken to determine the cause of the problem
- Steps to correct the problem and ensure that it will not reoccur
Document all steps taken in troubleshooting, even the ones that did not solve the issue. This documentation becomes a valuable reference should the same or similar problem occur again. Even in a small home network, good documentation saves hours of trying to remember how a problem was fixed in the past.
When a problem is first discovered in the network, it is important to verify it and determine how much of the network is affected by it. After the problem is confirmed, the first step in troubleshooting is to gather information. The following checklist provides some of the important information you should check.
- Nature of Problem
- End-user reports
- Problem verification report
- Equipment
- Manufacturer
- Make/model
- Firmware version
- Operating system version
- Ownership/warranty information
- Configuration and Topology
- Physical and logical topology
- Configuration files
- Log files
- Previous Troubleshooting
- Steps taken
- Results achieved
One of the first ways to gather information is to question the individual who reported the problem, as well as any other affected users. Questions can include end-user experiences, observed symptoms, error messages, and information about recent configuration changes to devices or applications.
Next, collect information about any equipment that may be affected. This can be gathered from documentation. A copy of all log files and a listing of any recent changes made to equipment configurations are also necessary. Log files are generated by the equipment itself and are usually obtainable through the management software. Other information on the equipment includes the manufacturer, make, and model of devices affected, as well as ownership and warranty information. The version of any firmware or software on the device is also important because there may be compatibility problems with particular hardware platforms.
Information about the network can also be gathered using network monitoring tools. Network monitoring tools are complex applications often used on large networks to continually gather information about the state of the network and network devices. These tools may not be available for smaller networks.
After all necessary information is gathered, start the troubleshooting process.