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Hardware & Network Troubleshooting

Study Guide

Hardware and network troubleshooting is the largest domain on Core 1 at 28%. You need to know the CompTIA troubleshooting methodology, how to diagnose hardware and network issues, and how to use diagnostic tools like multimeters, cable testers, and loopback plugs.

1CompTIA Troubleshooting Methodology

Follow these steps in order: 1) Identify the problem, 2) Establish a theory of probable cause, 3) Test the theory, 4) Establish a plan of action, 5) Implement the solution, 6) Verify full system functionality, 7) Document findings. Always start with the simplest solutions first (check cables, restart) before diving into complex diagnostics.

Examples:

•A PC won't turn on — first check: power cable plugged in, power switch on, outlet working
•No internet — first check: other devices can connect, cables are seated, Wi-Fi is enabled
•Blue Screen of Death — note the error code, check Event Viewer, test RAM with Windows Memory Diagnostic
2Common Hardware Failures

No POST (Power-On Self-Test): PC powers on but shows nothing — check RAM, GPU, CPU connections. Overheating: system shuts down or throttles — check fans, thermal paste, dust buildup. Drive failure: clicking/grinding noises from HDD, or drive not detected — replace drive. RAM failure: random crashes, blue screens — test with memory diagnostic tool.

Examples:

•A PC that beeps on startup is using POST beep codes to indicate hardware issues
•A clicking HDD means the read/write head is failing — back up immediately
•Overheating can be fixed by cleaning dust from fans, reapplying thermal paste, or improving case airflow
3Network Troubleshooting Commands

Windows commands for network troubleshooting: ipconfig shows IP configuration. ping tests connectivity to a host. tracert traces the route to a destination. nslookup tests DNS resolution. netstat shows active connections. arp shows the ARP table (IP-to-MAC mappings).

Examples:

•ipconfig /all shows detailed network info including DNS servers and MAC address
•ping 8.8.8.8 tests if you can reach the internet (bypasses DNS)
•nslookup google.com tests if DNS is resolving domain names to IP addresses
•tracert google.com shows each hop between your computer and the destination
4Diagnostic Tools

A multimeter measures voltage, current, and resistance — useful for testing power supplies and cables. A cable tester verifies cable continuity and correct pinout. A loopback plug tests a NIC by reflecting the signal back. A tone generator and probe (fox and hound) trace cables through walls. A POST card plugs into a motherboard to display error codes.

Examples:

•A multimeter set to DC voltage can verify a PSU is delivering correct voltages (3.3V, 5V, 12V)
•A loopback plug tests a network port by sending and receiving on the same port
•A cable tester can identify broken wires, shorts, and miswired connections in a network cable
5Mobile Device Troubleshooting

Mobile devices have unique troubleshooting considerations. Common issues include: apps crashing (clear cache, reinstall), battery draining fast (check background apps, screen brightness), no connectivity (toggle airplane mode, check SIM), and screen issues (recalibrate touchscreen, check for physical damage).

Examples:

•An app that keeps crashing can often be fixed by clearing its cache in Settings > Apps
•Poor battery life may be caused by apps running in the background — check battery usage stats
•If a phone won't connect to Wi-Fi, forget the network and re-enter the password
Test-Taking Tips
Always follow the CompTIA troubleshooting methodology in order — the exam tests this sequence.
Start with the simplest solution: check cables, restart the device, verify settings.
Know your port numbers — if ping works but nslookup doesn't, DNS (port 53) is likely the issue.
For mobile devices, a factory reset is a last resort after trying all other solutions.