Troubleshooting Methodology
CompTIA tests the order directly. A question gives you a scenario mid-way through and asks what to do next, and the answer is whichever step comes next in this list, not whichever action would fix it fastest.
Troubleshooting Methodology · firsttry.app/cheatsheets/troubleshooting-methodology · original reference written from published exam objectives. Not affiliated with any certification body.
The six steps, in order
| Step | What it involves | The trap |
|---|---|---|
| 1. Identify the problem | Question the user, identify changes, back up before changing anything | Skipping the backup |
| 2. Establish a theory | Question the obvious, research if needed | Testing before you have a theory |
| 3. Test the theory | Confirm it, or form a new one and test again | Fixing without confirming the cause |
| 4. Establish a plan of action | Consider impact, escalate if needed | Acting without considering side effects |
| 5. Verify full functionality | Confirm the fix and apply preventive measures | Stopping when the symptom disappears |
| 6. Document | Findings, actions and outcomes | Leaving nothing behind for the next person |
Network troubleshooting commands
| Command | What it tells you |
|---|---|
| ping | Whether a host answers, and round-trip time |
| ping 127.0.0.1 | Whether the local TCP/IP stack works |
| ipconfig / ifconfig / ip addr | Local addressing |
| ipconfig /all | DHCP server, DNS servers, MAC address |
| ipconfig /release and /renew | Get a fresh DHCP lease |
| ipconfig /flushdns | Clear a stale DNS cache |
| tracert / traceroute | Where along the path it stops |
| nslookup / dig | Whether name resolution works, and what it returns |
| netstat -ano / ss -tulpn | What is listening and connected |
| arp -a | Local MAC to IP mappings |
| pathping / mtr | Latency and loss per hop over time |
Working out where the fault is
| Symptom | Likely layer |
|---|---|
| No link light | Physical. Cable, port, or NIC |
| APIPA address 169.254.x.x | DHCP unreachable |
| Can ping IP but not name | DNS |
| Can ping local but not remote | Default gateway or routing |
| Intermittent loss on wireless only | Interference, channel overlap, or range |
| One application fails, others work | Application or firewall rule on that port |
| Slow for everyone at the same time | Congestion, duplex mismatch, or an upstream link |
Exams covered
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