The correct next step is to check the switch port configuration, specifically the VLAN assignment. This is because a workstation with a valid IP address and solid link lights confirms that Layer 1 (physical cabling) and Layer 3 (IP configuration) are functional, so the inability to ping the default gateway points to a Layer 2 issue—most commonly a VLAN mismatch where the switch port is assigned to a different VLAN than the workstation’s subnet, preventing frames from reaching the gateway. On the CompTIA Network+ N10-009 exam, this scenario tests your understanding of the OSI model layers and common troubleshooting flow; a common trap is to immediately suspect the gateway’s IP or the cable, but solid link lights and a valid IP rule those out. Remember the mnemonic “Ping fails, link is green? Check the VLAN between.”
N10-009 Network Troubleshooting Practice Question
This N10-009 practice question tests your understanding of network troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is troubleshooting a loss of network connectivity for a single workstation. The workstation has a valid IP address but cannot ping its default gateway. The link lights on both the workstation and the switch are solid. Which of the following should the technician check NEXT?
Why wrong: Since link lights are solid, the cable is likely functional at layer 1.
B
The switch port configuration, such as VLAN assignment
The port might be in the wrong VLAN, preventing communication with the gateway. Solid link lights indicate layer 1 is up but layer 2 may be misconfigured.
C
The DNS server settings
Why wrong: DNS is not involved in reaching the default gateway via IP.
D
The workstation's ARP cache
Why wrong: ARP cache issues would be a symptom, not a likely cause; the cache can be cleared, but the root cause is more likely a port configuration problem.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The switch port configuration, such as VLAN assignment
The workstation has a valid IP address and solid link lights, indicating Layer 1 (physical) and Layer 3 (IP configuration) are functional. The inability to ping the default gateway points to a Layer 2 issue, such as the switch port being in the wrong VLAN or having a misconfigured access/trunk setting. Checking the switch port configuration is the logical next step because VLAN mismatches prevent frames from reaching the gateway's subnet.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 cable integrity with a tester
Why it's wrong here
Since link lights are solid, the cable is likely functional at layer 1.
✓
The switch port configuration, such as VLAN assignment
Why this is correct
The port might be in the wrong VLAN, preventing communication with the gateway. Solid link lights indicate layer 1 is up but layer 2 may be misconfigured.
Related concept
Read the scenario before looking for a memorised answer.
ARP cache issues would be a symptom, not a likely cause; the cache can be cleared, but the root cause is more likely a port configuration problem.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that solid link lights guarantee full Layer 2 connectivity, when in fact they only indicate carrier detect and electrical synchronization, not correct VLAN membership or spanning-tree port state.
Detailed technical explanation
How to think about this question
When a switch port is assigned to a VLAN that does not match the workstation's subnet, the switch will drop frames destined for the gateway because the gateway's MAC address is in a different broadcast domain. The workstation may still have a valid IP address via DHCP if the DHCP server is on the same VLAN, but the gateway is unreachable. A common real-world scenario is a port accidentally left in the native VLAN (VLAN 1) while the workstation is on a different data VLAN.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Network Troubleshooting — This question tests Network Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The switch port configuration, such as VLAN assignment — The workstation has a valid IP address and solid link lights, indicating Layer 1 (physical) and Layer 3 (IP configuration) are functional. The inability to ping the default gateway points to a Layer 2 issue, such as the switch port being in the wrong VLAN or having a misconfigured access/trunk setting. Checking the switch port configuration is the logical next step because VLAN mismatches prevent frames from reaching the gateway's subnet.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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