Common symptoms - Learn Tech From Zero

5.5 Given a scenario, troubleshoot network issues.

📘CompTIA A+ Core 1 (220-1201)

Common Symptoms of Network Issues

When troubleshooting network problems, understanding the symptoms helps you figure out the root cause. Here’s a detailed look at the key ones:

1. Intermittent Wireless Connectivity

What it is:
The Wi-Fi connection keeps dropping and reconnecting.

Possible causes:

Weak Wi-Fi signal or the device is too far from the access point.
Wi-Fi channel conflicts with nearby networks.
Overloaded wireless network (too many devices connected).
Router or access point firmware issues.

What to check:

Check signal strength on the device.
Move closer to the Wi-Fi access point.
Change the Wi-Fi channel on the router to reduce interference.
Restart the access point/router.

2. Slow Network Speeds

What it is:
Webpages load slowly, downloads are slow, or streaming buffers frequently.

Possible causes:

High network traffic or too many devices using bandwidth.
Faulty or outdated network equipment (switch, router, cables).
Malware or background apps using the network.
ISP throttling or external network issues.

What to check:

Run a speed test to measure network performance.
Check for apps using high bandwidth.
Inspect cables and devices for faults.
Restart network equipment.

3. Limited Connectivity

What it is:
Device is connected to the network but cannot access the internet or other resources.

Possible causes:

Incorrect IP configuration (IP address conflict or misconfigured DHCP).
Gateway or DNS issues.
Firewall or security software blocking traffic.

What to check:

Run ipconfig (Windows) or ifconfig (Linux/macOS) to verify IP configuration.
Ping the default gateway to test connectivity.
Verify DNS settings and try accessing a website by IP address.

4. Jitter

What it is:
Variations in network latency, causing unstable connection performance, especially noticeable in real-time applications like VoIP or video calls.

Possible causes:

Network congestion.
Poor Wi-Fi signal or interference.
Low-quality network hardware.

What to check:

Test latency using tools like ping or traceroute.
Reduce network load or prioritize real-time traffic using Quality of Service (QoS) settings.

5. Poor Voice over Internet Protocol (VoIP) Quality

What it is:
VoIP calls have choppy audio, echoes, or dropped calls.

Possible causes:

High latency or jitter.
Packet loss in the network.
Insufficient bandwidth for voice traffic.

What to check:

Test network speed and latency.
Configure QoS for VoIP traffic.
Ensure network devices are not overloaded.

6. Port Flapping

What it is:
A network port on a switch repeatedly goes up and down, causing instability.

Possible causes:

Loose or faulty cables.
Misconfigured switch or loop in the network.
Network interface issues on the connected device.

What to check:

Inspect cables and connectors.
Check switch configuration for loops or errors.
Update switch firmware if needed.

7. High Latency

What it is:
Network takes a long time to respond to requests.

Possible causes:

Network congestion or overloaded devices.
Long physical distance or multiple hops between devices.
Poor routing configuration.

What to check:

Run ping or traceroute to identify delays.
Reduce unnecessary network traffic.
Check router and switch configurations.

8. External Interference

What it is:
Wireless networks experience disruption due to outside factors.

Possible causes:

Microwaves, cordless phones, or other electronics interfering with Wi-Fi.
Other Wi-Fi networks using the same channel.

What to check:

Move Wi-Fi devices away from potential sources of interference.
Change the Wi-Fi channel on the access point.
Use the 5 GHz band if interference is high on 2.4 GHz.

9. Authentication Failures

What it is:
Devices cannot connect to the network because credentials are rejected.

Possible causes:

Incorrect Wi-Fi password.
Expired user credentials in enterprise networks (like Active Directory).
Issues with security protocols (WPA2, WPA3).

What to check:

Verify credentials and re-enter the password.
Check network authentication server logs if available.
Ensure security settings on the device match the network.

10. Intermittent Internet Connectivity

What it is:
Internet connection works sometimes but drops randomly.

Possible causes:

ISP issues.
Modem or router instability.
Loose cables or faulty hardware.

What to check:

Test the connection with another device to rule out device-specific issues.
Reboot the modem/router.
Contact ISP if problems persist.

✅ Exam Tips

Know the difference between wireless and wired network issues.
Symptoms can overlap, so check multiple factors (signal, configuration, hardware).
Use built-in tools like ping, tracert, ipconfig, or Wi-Fi analyzers.
Focus on symptom → possible cause → troubleshooting step for questions.