Troubleshoot No Link Light on NIC: Check Switch Port
A technician is troubleshooting a workstation that cannot connect to the network. The link light on the NIC is off. The technician tests the Ethernet cable with a cable tester and it passes all four pairs. The workstation is connected to a wall jack that leads to a patch panel in the server room. The technician verifies that the patch cable from the patch panel to the switch is good. Which of the following should the technician do NEXT?
Quick Answer
The answer is to check the port status on the switch. This is correct because a link light that is off indicates a Layer 1 physical connectivity failure, and since the cable tester passed all four pairs and the patch cable is verified good, the issue must be at the switch port itself—such as the port being administratively shut down, error-disabled, or misconfigured. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your ability to isolate network hardware faults step by step, often tricking test-takers into re-testing cables or replacing the NIC when the real problem is a disabled switch port. A common memory tip is to remember that the link light is the first clue: if cables are good, the switch port is the next suspect. Think “Link off, cables fine, check the switch line.”
⚠ Common exam trap
The trap here is that candidates often jump to replacing the NIC or re-terminating the cable when the link light is off, forgetting that the switch port itself may be disabled or misconfigured, which is a faster and more logical check.
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
✓
Check the port status on the switch
The link light being off indicates no physical layer (Layer 1) connectivity. Since the cable tester passed all four pairs and the patch cable is verified good, the issue likely lies with the switch port itself. Checking the port status on the switch (e.g., using 'show interfaces status' or verifying PoE/administrative shutdown) is the logical next step to confirm if the port is enabled, not error-disabled, or configured correctly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace the NIC
Why it's wrong here
Replacing the NIC should be done only after verifying that the switch port is active and the cable path is fully intact. The link light being off could also be due to a disabled port.
- ✗
Re-terminate the wall jack
Why it's wrong here
The cable tester passed all pairs, so the termination at the wall jack is likely correct. Re-terminating is unnecessary at this point.
- ✓
Check the port status on the switch
Why this is correct
The switch port may be administratively disabled, faulty, or not configured for the correct VLAN. Checking the switch port status is the most efficient next step to identify the problem.
- ✗
Change the workstation's IP address to static
Why it's wrong here
An IP address configuration issue would not cause the link light to be off. The link light indicates physical connectivity, so the problem is at Layer 1 or Layer 2.
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
Related to this question
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Same concept, more angles
2 more ways this is tested on 220-1101
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a workstation that cannot connect to the network. The technician sees that the Ethernet cable used is a crossover cable. The workstation's network adapter supports Auto-MDI/X. The switch port does not have any link light. Which of the following is the MOST likely reason for the lack of connectivity?
medium- ✓ A.The crossover cable is faulty
- B.The switch does not support Auto-MDI/X
- C.The NIC driver is out of date
- D.The cable length exceeds 100 meters
Why A: The NIC supports Auto-MDI/X, so it can automatically adjust its internal crossover configuration for either a straight-through or crossover cable, regardless of the switch's support. Since the switch port has no link light, the crossover cable itself is not the issue (the NIC can handle it). The most likely reason is a defective cable, making option A correct.
Variation 2. A technician installs a new network interface card (NIC) into a desktop computer. After installation, the computer boots normally and the NIC is detected in Device Manager without errors. When an Ethernet cable is connected, the link light does not light up on the NIC or the switch port. The cable is known to work with another computer. The technician tries a different port on the same switch, but the link light remains off. Which of the following should the technician do NEXT?
hard- A.Update the NIC driver from the manufacturer's website
- B.Disable and re-enable the NIC in Device Manager
- C.Check the NIC's configuration for a disabled port
- ✓ D.Reseat the NIC in the PCIe slot
Why D: Since the NIC is detected in Device Manager without errors and the cable works on another computer, the issue is likely a physical connection problem. Reseating the NIC ensures proper contact with the PCIe slot, which can resolve intermittent connectivity or poor electrical contact that prevents the link light from activating.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.