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← 200-301
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mediummultiple choiceObjective-mapped

Exhibit

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

Exhibit: 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?

Question 1mediummultiple choice
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Exhibit: 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?

Full question →

Answer choices

Why each option matters

Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.

A

Best answer

The access VLAN for the PC is misconfigured

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

B

Distractor review

The voice VLAN should always match the access VLAN

They are commonly different.

C

Distractor review

PortFast blocks the PC from sending traffic

PortFast is usually appropriate on such a port.

D

Distractor review

The phone requires the switch to be in trunk mode

An access port with voice VLAN is a normal design.

Common exam trap

Common exam trap: answer the scenario, not the keyword

A common exam trap is believing that the voice VLAN must match the access VLAN or that the switch port must be configured as a trunk to support IP phones. This misconception leads candidates to overlook the need for a correctly configured access VLAN for the PC’s untagged traffic. Since the phone tags its traffic with the voice VLAN, it continues to work even if the access VLAN is wrong or missing, causing confusion. The exam tests understanding that voice VLAN and access VLAN are distinct and that the PC relies on the access VLAN for network connectivity.

Technical deep dive

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.

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More questions from this exam

Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.

Question 1

A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?

Question 2

A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?

Question 3

What is the OSPF metric called?

Question 4

A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?

Question 5

A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?

Question 6

A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?

FAQ

Questions learners often ask

What does this 200-301 question test?

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?

Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.

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