Question 1hardmultiple choice
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Question 76 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network administrator is deploying a new IP…
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 GigabitEthernet0/1 description Desktop with VoIP switchport mode access switchport access vlan 10 switchport voice vlan 20 spanning-tree portfast no shutdown
A network administrator is deploying a new IP phone for a remote user. The phone is connected to a Cisco switch port configured as an access port for voice and data VLANs. The PC connected to the phone’s pass-through port can access the network, but the IP phone cannot obtain an IP address and fails to register. The switch interface shows up/up. Which command is most likely missing from the switchport configuration?
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.
Clue:
"which command"Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
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
✓
switchport mode trunk
The IP phone requires the switch port to be configured with 'switchport voice vlan' to tag voice traffic. However, the switchport mode is set to 'access', which only allows untagged traffic on the access VLAN. For the phone to send and receive tagged voice frames, the port must be in 'switchport mode trunk' or have 'switchport mode access' with 'switchport voice vlan' enabled. The missing command is 'switchport mode trunk' (or removing 'switchport mode access' and allowing dynamic trunking). In this scenario, the phone cannot communicate because the switch expects untagged frames on VLAN 10, but the phone sends tagged frames on VLAN 20. The PC works because it sends untagged frames which are accepted on VLAN 10.
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.
- ✓
switchport mode trunk
Why this is correct
This command changes the port to trunk mode, allowing both VLAN 10 (native) and VLAN 20 (tagged) traffic. The IP phone will then send tagged voice frames on VLAN 20, and the PC will send untagged data frames on VLAN 10.
Clue confirmation
The clue words "most likely", "which command" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✗
switchport port-security maximum 2
Why it's wrong here
Port security limits the number of MAC addresses; it does not affect VLAN tagging or phone registration.
- ✗
switchport access vlan 20
Why it's wrong here
Changing the access VLAN to 20 would move the PC to VLAN 20, but the phone would still send untagged frames on VLAN 20, which might work but breaks voice/data separation. However, the correct solution is to allow both VLANs via trunking.
- ✗
spanning-tree portfast trunk
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.
✓switchport mode trunkCorrect answer▾
Why this is correct
This command changes the port to trunk mode, allowing both VLAN 10 (native) and VLAN 20 (tagged) traffic. The IP phone will then send tagged voice frames on VLAN 20, and the PC will send untagged data frames on VLAN 10.
✗switchport port-security maximum 2Wrong answer — click to see why▾
Why this is wrong here
The symptom is not about MAC address limits; the phone cannot get an IP address due to VLAN mismatch.
✗switchport access vlan 20Wrong answer — click to see why▾
Why this is wrong here
This would place both devices in the same VLAN, defeating the purpose of separate voice and data VLANs, and may not resolve the phone's need for tagged traffic.
✗spanning-tree portfast trunkWrong answer — click to see why▾
Why this is wrong here
The phone's inability to get an IP is due to VLAN mismatch, not spanning-tree delay.
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: switchport mode trunk — The IP phone requires the switch port to be configured with 'switchport voice vlan' to tag voice traffic. However, the switchport mode is set to 'access', which only allows untagged traffic on the access VLAN. For the phone to send and receive tagged voice frames, the port must be in 'switchport mode trunk' or have 'switchport mode access' with 'switchport voice vlan' enabled. The missing command is 'switchport mode trunk' (or removing 'switchport mode access' and allowing dynamic trunking). In this scenario, the phone cannot communicate because the switch expects untagged frames on VLAN 10, but the phone sends tagged frames on VLAN 20. The PC works because it sends untagged frames which are accepted on VLAN 10.
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", "which command". 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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