Core 1 · 28% exam weight

Hardware & Network Troubleshooting: a practical CompTIA A+ guide

A repeatable diagnostic workflow under real help-desk constraints. Learn the mental models, common failure modes, and evidence-based troubleshooting steps.

220-1201V15 objectives4 deep-dive sections

How to use this guide: Read one section, explain the concept in your own words, then walk through each support case without looking at the suggested diagnostic path. A strong tech tests a hypothesis before replacing parts.

01. The six-step process

Identify the problem; establish a theory; test the theory; plan and implement a fix; verify full system functionality and preventive measures; document findings. Preserve user data and obtain approval before risky changes. If your theory fails, establish a new one—do not stack random fixes.

02. Use scope to find the fault domain

One user versus an entire floor suggests very different causes. If an entire VLAN fails, investigate switch uplinks, addressing services, and routing. If one host fails, inspect its adapter, cable, configuration and recent changes. Check whether the issue is reproducible, time-dependent or load-dependent.

03. Distinguish similar symptoms

No power: no fans/lights. No POST: power but hardware initialization fails. No display: check external/internal monitor path. No boot: POST succeeds but firmware cannot locate a bootable OS. A system that shuts down under CPU load is not the same as one that loses power randomly even when idle.

04. Change control and verification

Restore the user’s service safely, but do not declare success after a single ping if the issue was a failed video meeting. Reproduce the original use case and document baseline, changes, result, and rollback. Escalate appropriately if you lack permission or specialized access.

Apply the lesson: real support cases

Support case 1

A new switch uplink causes many desks to lose internet but local printers still work. Look at gateway, trunk/VLAN, and uplink before changing every PC.

Support case 2

A laptop repeatedly shuts down during video rendering after being serviced. Inspect fan engagement, heatsink seating and temperature before reinstalling software.

Exam-day decision rule: Use the symptom and the blast radius to constrain a theory, then verify the original workflow.

Practice this material →

These are original explanatory notes aligned to the named exam domains; review the current official objectives for exact scope. The mock exam is practice only and is not scored on CompTIA's scale.