220-1101 Hardware and Network Troubleshooting Practice Question
A technician is troubleshooting a workstation that lost network connectivity after a lightning storm. The workstation's Ethernet link light on both the NIC and the switch port is solid, but the workstation cannot access any network resources. The technician can ping 127.0.0.1 successfully. When pinging the default gateway (192.168.1.1), the request times out. The technician connects a known-good laptop to the same switch port and cable, and the laptop accesses the network normally. Which of the following is the MOST likely cause?
⚠ Common exam trap
Many candidates assume a solid link light guarantees full Layer 2 functionality, but the CompTIA exam tests that link lights only confirm Layer 1 connectivity, not the integrity of frame processing at Layer 2.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The lightning storm damaged the NIC, causing it to fail at the data link layer while maintaining a physical link.
The solid link light indicates a physical layer (Layer 1) connection is established, and the successful ping to 127.0.0.1 confirms the TCP/IP stack is functioning. However, the inability to ping the default gateway, combined with a known-good laptop working on the same port and cable, isolates the fault to the workstation's NIC. The most likely cause is that the lightning storm damaged the NIC at the data link layer (Layer 2), allowing link pulses (Layer 1) to pass but corrupting frame processing, which prevents successful ARP and IP communication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The workstation's IP address is statically configured with an incorrect subnet mask.
Why it's wrong here
While an incorrect subnet mask could prevent pinging the default gateway, the technician did not verify the IP settings. However, the fact that a known-good laptop works on the same port suggests that the network configuration on the workstation is likely incorrect. But a static IP with wrong mask would not cause the exact symptom described (link lights on, successful loopback). Additionally, the scenario implies the workstation was working before the storm, so configuration change is less likely than a hardware issue.
- ✓
The lightning storm damaged the NIC, causing it to fail at the data link layer while maintaining a physical link.
Why this is correct
A solid link light indicates Layer 1 connectivity, but the NIC may still be damaged and unable to process frames properly. This is a common after-effect of a power surge, where the transceiver gets fried but the carrier detection circuits survive. Replacing the NIC resolves the issue.
- ✗
The switch port is configured with the incorrect VLAN, but the link light remains on because the switch port is up.
Why it's wrong here
If the switch port had an incorrect VLAN, the workstation might not be able to communicate with the default gateway. However, the known-good laptop worked on the same port, which indicates the port configuration is correct. The laptop's success proves the VLAN assignment is fine.
- ✗
The workstation's network cable is faulty and only passes link pulses but not data frames.
Why it's wrong here
If the cable were faulty in a way that prevented data transmission, the link light might still be solid, but the known-good laptop would also fail. Since the laptop worked, the cable is functional for data. The issue is specific to the workstation's NIC.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
Go deeper
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Key term
Media Access Control
Media Access Control (MAC) is a sublayer of the Data Link Layer in networking that controls how devices on the same network share access to the physical medium and uniquely identifies each device with a hardware address.
Key term
TCP
TCP is a connection-oriented transport layer protocol that ensures reliable, ordered, and error-checked delivery of data between applications over IP networks.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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