Question 1hardmultiple choice
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Question 1,460 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network administrator has configured a switch…
This 200-301 practice question tests your understanding of 200-301 exam topics. 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.
Exhibit
interface GigabitEthernet1/0/24 description VoIP and Desktop switchport mode access switchport access vlan 10 switchport voice vlan 20 spanning-tree portfast !
A network administrator has configured a switch port to support a VoIP phone and a desktop PC. Users report that the desktop PC cannot obtain an IP address via DHCP, while the VoIP phone registers successfully. The switch port is up/up, and the desktop is connected to the phone's PC port. What is the most likely cause of the issue?
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 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 switchport access vlan 10 should be changed to vlan 20 to match the data vlan expected by the desktop.
The desktop PC is unable to obtain an IP address because the switchport access vlan 10 is configured for data traffic, but the switchport voice vlan 20 is configured for voice traffic. The desktop is connected to the phone's PC port, which typically passes data traffic untagged. However, the switchport access vlan 10 is set to vlan 10, and the desktop should be in the same vlan as the DHCP server. The issue is that the access vlan is misconfigured; it should be vlan 20 for data or the DHCP server must be in vlan 10. The correct fix is to change the access vlan to match the desktop's expected vlan, or ensure the DHCP server is in vlan 10. Option B is correct because it identifies the access vlan mismatch. Options A, C, and D are incorrect: A would not affect DHCP; C would break VoIP; D is unrelated to the symptom.
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 switchport mode access should be changed to switchport mode trunk to allow both vlans.
Why it's wrong here
Changing to trunk mode would require the phone to tag traffic, which might not be supported and could cause further issues.
- ✓
The switchport access vlan 10 should be changed to vlan 20 to match the data vlan expected by the desktop.
Why this is correct
The desktop is connected to the phone's PC port, which typically forwards data untagged. The access vlan determines the untagged vlan. If the DHCP server is in vlan 20, the access vlan must be vlan 20 for the desktop to receive an 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 switchport voice vlan 20 should be removed because the desktop cannot use the voice vlan.
Why it's wrong here
Removing the voice vlan would prevent the VoIP phone from registering, as it needs a dedicated voice vlan.
- ✗
The spanning-tree portfast should be disabled to prevent DHCP delays.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The switchport access vlan 10 should be changed to vlan 20 to match the data vlan expected by the desktop.Correct answer▾
Why this is correct
The desktop is connected to the phone's PC port, which typically forwards data untagged. The access vlan determines the untagged vlan. If the DHCP server is in vlan 20, the access vlan must be vlan 20 for the desktop to receive an IP.
✗The switchport mode access should be changed to switchport mode trunk to allow both vlans.Wrong answer — click to see why▾
Why this is wrong here
The current configuration uses access mode with voice vlan, which is correct for a phone+PC setup. Trunk mode is unnecessary and could break the phone's untagged traffic expectations.
✗The switchport voice vlan 20 should be removed because the desktop cannot use the voice vlan.Wrong answer — click to see why▾
Why this is wrong here
The voice vlan is correctly configured for the phone; the problem is with the data vlan assignment for the desktop.
✗The spanning-tree portfast should be disabled to prevent DHCP delays.Wrong answer — click to see why▾
Why this is wrong here
Portfast is beneficial for host ports; disabling it would worsen the issue by introducing STP convergence delays.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
What to study next
Got this wrong? Here's your next step.
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 200-301 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: The switchport access vlan 10 should be changed to vlan 20 to match the data vlan expected by the desktop. — The desktop PC is unable to obtain an IP address because the switchport access vlan 10 is configured for data traffic, but the switchport voice vlan 20 is configured for voice traffic. The desktop is connected to the phone's PC port, which typically passes data traffic untagged. However, the switchport access vlan 10 is set to vlan 10, and the desktop should be in the same vlan as the DHCP server. The issue is that the access vlan is misconfigured; it should be vlan 20 for data or the DHCP server must be in vlan 10. The correct fix is to change the access vlan to match the desktop's expected vlan, or ensure the DHCP server is in vlan 10. Option B is correct because it identifies the access vlan mismatch. Options A, C, and D are incorrect: A would not affect DHCP; C would break VoIP; D is unrelated to the symptom.
What should I do if I get this 200-301 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 200-301 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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