How it works
Problems on a device rarely announce their cause, because hardware, software, and network layers all sit between you and the symptom. A process exists so that you narrow the field instead of guessing.
Gather information about what changed and when, try the cheap and non-disruptive fixes first, then work toward the expensive ones. Verify after every change rather than at the end.
Common error
A fix that was not verified is not a fix. If the symptom persists after a reasonable change, consider that there may be more than one fault, or that the cause was misidentified.
Worked example
A laptop stopped reaching the school portal after a wireless settings change. Other laptops on the same network still work. Choose a first investigation step.
Evidence
Affected devices: 1
Change: manual wireless profile
Other devices: portal reachableThe scope suggests a device-specific problem, although it does not prove a cause. Record the current profile and address settings, compare them with a working device, and test a reversible correction. Verify both portal access and ordinary network use before closing the incident.
Exercises
1.1.1
A tablet loses access after a profile change. Explain why rebooting every access point is a poor first action.
Show solution
Only one tablet is affected and the timing points to its profile. Restarting shared equipment disrupts unrelated users without testing that hypothesis. Compare the tablet configuration with a known working device first.
1.1.2
Write a four-step investigation record for a wrong gateway discovered on that tablet.
Show solution
Record the symptom and affected device; identify the configured gateway as inconsistent with the network plan; restore the approved setting or automatic configuration; verify local and remote access and document the result.