The answer is a VLAN mismatch on the switch port. This is correct because the workstation can ping its own IP, confirming the NIC, TCP/IP stack, and IP configuration are functioning properly at Layer 3, but it cannot reach the default gateway, which points to a Layer 2 connectivity issue. When a switch port is assigned to a different VLAN than the workstation, frames from the device never reach the gateway’s broadcast domain, even though the IP addressing appears valid. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your ability to distinguish between Layer 2 and Layer 3 problems; a common trap is to blame the IP configuration or cable when the link light is solid and the IP is correct. Remember the memory tip: “Ping self works, ping gateway fails—think VLAN rails.”
220-1101 Network Troubleshooting Practice Question
This 220-1201 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 network where a single workstation cannot access any network resources. The link light on the NIC is solid, and the IP configuration shows an address of 192.168.1.100 with a subnet mask of 255.255.255.0. The workstation can ping its own IP but not the default gateway (192.168.1.1). What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 is configured with the wrong VLAN.
The workstation has a valid IP and can ping itself, indicating the NIC and stack are working. However, it cannot reach the gateway, which suggests a Layer 2 issue—likely an incorrect or missing default gateway configuration, or a VLAN mismatch on the switch port.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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 DNS server is unreachable.
Why it's wrong here
Incorrect—DNS is not needed to ping an IP address; the issue is with Layer 3 routing.
✓
The switch port is configured with the wrong VLAN.
Why this is correct
Correct—if the switch port is in a different VLAN, the workstation cannot reach the gateway, even with a valid IP.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
The Ethernet cable is a crossover cable.
Why it's wrong here
Incorrect—modern switches auto-MDIX, so crossover cables work fine; this would not cause a gateway issue.
✗
The workstation's subnet mask is wrong.
Why it's wrong here
Incorrect—the subnet mask is correct for a /24 network; a wrong mask would cause different symptoms.
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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 220-1201 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 220-1201 questions on switching, trunking, and access-port configuration.
Network Troubleshooting — This question tests Network Troubleshooting — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The switch port is configured with the wrong VLAN. — The workstation has a valid IP and can ping itself, indicating the NIC and stack are working. However, it cannot reach the gateway, which suggests a Layer 2 issue—likely an incorrect or missing default gateway configuration, or a VLAN mismatch on the switch port.
What should I do if I get this 220-1201 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 220-1201 questions on switching, trunking, and access-port configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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