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Switching and Network Access →mediumMultiple ChoiceObjective-mapped

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. A key principle to apply: a Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged.. 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 gi1/0/10
 switchport mode access
 switchport access vlan 999
 switchport voice vlan 20
 spanning-tree portfast

A user says the phone connected to a switch port works, but the attached PC does not get network access. What is the most likely switch-side 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.

Question 1mediummultiple choice
Full question →

Exhibit

interface gi1/0/10
 switchport mode access
 switchport access vlan 999
 switchport voice vlan 20
 spanning-tree portfast

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 access VLAN for the PC is misconfigured

An IP phone can use a voice VLAN while the attached PC uses the access VLAN. If the access VLAN is missing or wrong, the phone may still work while the PC fails.

Key principle: A Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged.

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 access VLAN for the PC is misconfigured

    Why this is correct

    The PC uses the access VLAN, not the voice VLAN.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    A Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged.

  • ✗

    The voice VLAN should always match the access VLAN

    Why it's wrong here

    They are commonly different.

  • ✗

    PortFast blocks the PC from sending traffic

    Why it's wrong here

    PortFast is usually appropriate on such a port.

  • ✗

    The phone requires the switch to be in trunk mode

    Why it's wrong here

    An access port with voice VLAN is a normal design.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Ensure you understand the difference between voice and access VLANs and how they affect different devices on the same port.

Detailed technical explanation

How to think about this question

In Cisco networking, when an IP phone and a PC connect to the same switch port, the port typically operates as an access port with a configured voice VLAN. The IP phone tags its voice traffic with the voice VLAN, while the PC sends untagged data traffic that the switch associates with the access VLAN. This separation allows the switch to handle voice and data traffic differently, ensuring quality of service for voice and proper network segmentation for data. The switch port configuration must explicitly define both the access VLAN for the PC and the voice VLAN for the phone. If the access VLAN is misconfigured or missing, the PC’s untagged frames will not be assigned to the correct VLAN, resulting in no network connectivity for the PC. Meanwhile, the phone continues to function correctly because it tags its traffic with the voice VLAN, which is properly configured and recognized by the switch. A common exam trap is assuming that the voice VLAN must match the access VLAN or that the port should be in trunk mode for the phone to work. In practice, the voice VLAN is distinct from the access VLAN, and the port remains an access port with voice VLAN configured. Misunderstanding this leads to misconfiguration and connectivity issues for the PC, even though the phone works fine, which is the scenario described in the question.

KKey Concepts to Remember

  • A Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged.
  • The access VLAN on a switch port determines the VLAN membership for untagged frames sent by devices like PCs connected behind IP phones.
  • If the access VLAN is misconfigured or missing, the PC connected to the IP phone will fail to obtain network access despite the phone working correctly.
  • Voice VLAN and access VLAN are commonly different and must be configured separately to support both voice and data on the same physical port.
  • Switch ports connecting IP phones and PCs typically operate as access ports with a voice VLAN, not as trunk ports.
  • PortFast does not block traffic from PCs; it is used to speed up port transition to forwarding state and is appropriate for ports with end devices.
  • The switch uses VLAN tagging to differentiate voice traffic from data traffic, ensuring proper QoS and network segmentation.
  • Misconfiguring VLANs on switch ports is a frequent cause of connectivity problems in networks with IP phones and attached PCs.

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

A Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged.

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 a Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged., then practise related 200-301 questions on the same topic to reinforce the concept.

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FAQ

Questions learners often ask

What does this 200-301 question test?

Switching and Network Access — This question tests Switching and Network Access — A Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged..

What is the correct answer to this question?

The correct answer is: The access VLAN for the PC is misconfigured — An IP phone can use a voice VLAN while the attached PC uses the access VLAN. If the access VLAN is missing or wrong, the phone may still work while the PC fails.

What should I do if I get this 200-301 question wrong?

Review a Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged., then practise related 200-301 questions on the same topic to reinforce the concept.

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?

A Cisco switch port configured with a voice VLAN separates voice traffic from data traffic by tagging voice frames and leaving data frames untagged.

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Last reviewed: May 17, 2026

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