Chapter 18 Troubleshooting : Troubleshooting methodologies : Define the problem
  
Define the problem
The following questions can help determine the scope of the problem and isolate it:
What is the problem?
Do not assume that the problem is being experienced is the actual problem. First determine that the problem does not lie elsewhere before starting to troubleshoot the FortiGate device.
Has it ever worked before?
If the device never worked from the first day, you may not want to spend time troubleshooting something that could well be defective. See “Troubleshooting bootup”
Can the problem be reproduced at will or is it intermittent?
If the problem is intermittent, it may be dependent on system load. Also an intermittent problem can be very difficult to troubleshoot due to the difficulty reproducing the issue.
What has changed?
Do not assume that nothing has changed in the network. Use the FortiGate event log to see if any configuration changes were made. The change could be in the operating environment, for example, a gradual increase in load as more sites are forwarded through the firewall.
If something has changed, see what the affect is if the change is rolled back.
Determine the scope of the problem - after you have isolated the problem what applications, users, devices, and operating systems does it effect?
 
Before you can solve a problem, you need to understand it. Often this step can be the longest in this process.
Ask questions such as:
What is not working? Be specific.
Is there more than one thing not working?
Is it partly working? If so, what parts are working?
Is it a connectivity issue for the whole device, or is there an application that isn’t reaching the Internet?
Be as specific as possible with your answers, even if it takes awhile to find the answers.
These questions will help you define the problem. Once the problem is defined, you can search for a solution and then create a plan on how to solve it.