The answer is to configure `switchport voice vlan 20` and `power inline auto` on interfaces Gi0/1 and Gi0/2, and `power inline auto` on Gi0/3, which is set as a trunk with native VLAN 100. This is correct because IP phones require a separate voice VLAN to tag their traffic, while the access point on Gi0/3 needs PoE and must operate on the native VLAN of a trunk to pass multiple VLANs. On the CCNA 200-301 v2 exam, this tests your understanding of voice VLAN and PoE configuration as part of switchport security and QoS fundamentals—a common trap is forgetting that the AP port must be a trunk, not an access port, and that PoE is disabled by default on Cisco switches. Remember the mnemonic: “Phones need voice, APs need trunk, both need power.”
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. 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.
Network Topology
You are connected to SW1. This is a Layer 2 switch that connects multiple IP phones and an AP. The AP is on Gi0/3 and must receive PoE and be placed in VLAN 100 (native VLAN). IP phones on Gi0/1 and Gi0/2 must use VLAN 20 for voice and VLAN 10 for data, and must receive PoE. Currently, the AP cannot get an IP address and the phones have no voice connectivity. Configure SW1 to fix these issues.
interface Gi0/1; switchport voice vlan 20; power inline auto; interface Gi0/2; switchport voice vlan 20; power inline auto; interface Gi0/3; power inline auto
This configuration correctly enables PoE on all three interfaces and assigns voice VLAN 20 to the phone ports, which is necessary for IP phones to obtain voice connectivity. The AP port already has access VLAN 100 configured, so adding PoE resolves the AP's inability to get an IP address.
B
interface Gi0/1; switchport voice vlan 10; power inline auto; interface Gi0/2; switchport voice vlan 10; power inline auto; interface Gi0/3; switchport access vlan 100; power inline auto
Why wrong: This is incorrect because the voice VLAN should be VLAN 20, not VLAN 10. VLAN 10 is designated for data traffic on the phone ports, so using it as the voice VLAN would cause the phones to use the data VLAN for voice, breaking voice connectivity.
Why wrong: This is incorrect because it omits the 'power inline auto' command on all interfaces. Without PoE enabled, the AP and IP phones will not receive power and will not function, even if VLAN configurations are correct.
D
interface Gi0/1; power inline auto; interface Gi0/2; power inline auto; interface Gi0/3; power inline auto; switchport trunk native vlan 100
Why wrong: This is incorrect because it does not configure the voice VLAN on Gi0/1 and Gi0/2, which is essential for IP phones to separate voice and data traffic. Additionally, changing the trunk native VLAN is unnecessary and may cause issues if the upstream switch expects a different native VLAN.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
interface Gi0/1; switchport voice vlan 20; power inline auto; interface Gi0/2; switchport voice vlan 20; power inline auto; interface Gi0/3; power inline auto
The AP on Gi0/3 requires PoE (power inline auto) and must be on a trunk port with native VLAN 100. The current configuration likely lacks PoE, and the port may be set as an access port instead of a trunk. For the IP phones on Gi0/1 and Gi0/2, the missing 'switchport voice vlan 20' command prevents voice traffic from using VLAN 20, and PoE must also be enabled. The provided solution adds the necessary voice VLAN and PoE commands. Option A is correct because it applies voice VLAN 20 and PoE to the phone ports, and PoE to the AP port. Option B incorrectly assigns voice VLAN 10; Option C omits PoE on the AP port; Option D applies PoE globally but fails to set voice VLANs and incorrectly configures trunk native VLAN on all ports.
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.
✓
interface Gi0/1; switchport voice vlan 20; power inline auto; interface Gi0/2; switchport voice vlan 20; power inline auto; interface Gi0/3; power inline auto
Why this is correct
This configuration correctly enables PoE on all three interfaces and assigns voice VLAN 20 to the phone ports, which is necessary for IP phones to obtain voice connectivity. The AP port already has access VLAN 100 configured, so adding PoE resolves the AP's inability to get an IP address.
Related concept
Access ports place end devices into a single VLAN.
✗
interface Gi0/1; switchport voice vlan 10; power inline auto; interface Gi0/2; switchport voice vlan 10; power inline auto; interface Gi0/3; switchport access vlan 100; power inline auto
Why it's wrong here
This is incorrect because the voice VLAN should be VLAN 20, not VLAN 10. VLAN 10 is designated for data traffic on the phone ports, so using it as the voice VLAN would cause the phones to use the data VLAN for voice, breaking voice connectivity.
This is incorrect because it omits the 'power inline auto' command on all interfaces. Without PoE enabled, the AP and IP phones will not receive power and will not function, even if VLAN configurations are correct.
✗
interface Gi0/1; power inline auto; interface Gi0/2; power inline auto; interface Gi0/3; power inline auto; switchport trunk native vlan 100
Why it's wrong here
This is incorrect because it does not configure the voice VLAN on Gi0/1 and Gi0/2, which is essential for IP phones to separate voice and data traffic. Additionally, changing the trunknative VLAN is unnecessary and may cause issues if the upstream switch expects a different native VLAN.
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.
✓interface Gi0/1; switchport voice vlan 20; power inline auto; interface Gi0/2; switchport voice vlan 20; power inline auto; interface Gi0/3; power inline autoCorrect answer▾
Why this is correct
This configuration correctly enables PoE on all three interfaces and assigns voice VLAN 20 to the phone ports, which is necessary for IP phones to obtain voice connectivity. The AP port already has access VLAN 100 configured, so adding PoE resolves the AP's inability to get an IP address.
✗interface Gi0/1; switchport voice vlan 10; power inline auto; interface Gi0/2; switchport voice vlan 10; power inline auto; interface Gi0/3; switchport access vlan 100; power inline autoWrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the voice VLAN is set to VLAN 10 instead of VLAN 20, which contradicts the requirement that voice traffic uses VLAN 20.
Why candidates choose this
Candidates might confuse the data VLAN (10) with the voice VLAN (20) or assume that the same VLAN can serve both purposes, especially if they misread the scenario.
The specific factual error is the failure to enable PoE on the interfaces, which is required for both the AP and IP phones to operate.
Why candidates choose this
Candidates might focus solely on VLAN configuration and forget that PoE is necessary for devices that draw power from the switch, especially if they assume PoE is enabled by default.
✗interface Gi0/1; power inline auto; interface Gi0/2; power inline auto; interface Gi0/3; power inline auto; switchport trunk native vlan 100Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is the omission of the 'switchport voice vlan 20' command on the phone ports, leaving them without voice VLAN assignment.
Why candidates choose this
Candidates might think that PoE alone is sufficient for phones to work, or they might focus on trunk configuration instead of access port voice VLAN, especially if they misunderstand the role of native VLAN.
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.
Trap categories for this question
Command / output trap
This is incorrect because it omits the 'power inline auto' command on all interfaces. Without PoE enabled, the AP and IP phones will not receive power and will not function, even if VLAN configurations are correct.
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 200-301 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 200-301 questions on switching, trunking, and access-port configuration.
Switching and Network Access — This question tests Switching and Network Access — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: interface Gi0/1; switchport voice vlan 20; power inline auto; interface Gi0/2; switchport voice vlan 20; power inline auto; interface Gi0/3; power inline auto — The AP on Gi0/3 requires PoE (power inline auto) and must be on a trunk port with native VLAN 100. The current configuration likely lacks PoE, and the port may be set as an access port instead of a trunk. For the IP phones on Gi0/1 and Gi0/2, the missing 'switchport voice vlan 20' command prevents voice traffic from using VLAN 20, and PoE must also be enabled. The provided solution adds the necessary voice VLAN and PoE commands. Option A is correct because it applies voice VLAN 20 and PoE to the phone ports, and PoE to the AP port. Option B incorrectly assigns voice VLAN 10; Option C omits PoE on the AP port; Option D applies PoE globally but fails to set voice VLANs and incorrectly configures trunk native VLAN on all ports.
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.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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