Question 1hardmultiple choice
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Question 1,161 of 1,052
hardmultiple choiceObjective-mapped
CCNA Practice Question: A network administrator is deploying a new VoIP…
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 switchport mode access switchport access vlan 10 switchport voice vlan 20 spanning-tree portfast service-policy input QOS_POLICY
A network administrator is deploying a new VoIP phone on switch port Gi0/1. The phone powers on and is recognized by the switch, but it cannot obtain an IP address via DHCP. The desktop PC connected through the phone's pass-through port also fails to get an IP. The switch port configuration is shown below. 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 is missing or the VLAN does not exist; ensure VLAN 10 is created and allowed on the trunk.
The port is configured with both an access VLAN (10) and a voice VLAN (20). The switchport voice vlan command is used to separate voice traffic into a dedicated VLAN, but the phone must be able to communicate on the access VLAN to obtain an IP address for the PC. The problem is that the access VLAN 10 is not present on the switch or is not allowed on the trunk to the DHCP server. The correct answer is to ensure VLAN 10 exists and is allowed on the uplink. The other options are incorrect because the voice VLAN is correctly configured, PortFast and QoS policies do not affect DHCP, and the native VLAN mismatch would cause different symptoms.
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 voice VLAN is misconfigured; it should be the same as the access VLAN.
Why it's wrong here
Voice and data should be on separate VLANs for traffic separation.
- ✓
The switchport access vlan 10 is missing or the VLAN does not exist; ensure VLAN 10 is created and allowed on the trunk.
- ✗
The spanning-tree portfast should be removed because it can cause DHCP issues.
- ✗
The service-policy input QOS_POLICY is blocking DHCP packets.
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 is missing or the VLAN does not exist; ensure VLAN 10 is created and allowed on the trunk.Correct answer▾
Why this is correct
If VLAN 10 is not present or not allowed on the trunk, the PC and phone cannot communicate with the DHCP server.
✗The voice VLAN is misconfigured; it should be the same as the access VLAN.Wrong answer — click to see why▾
Why this is wrong here
The voice VLAN is correctly configured as a separate VLAN; combining them would defeat the purpose of QoS.
✗The spanning-tree portfast should be removed because it can cause DHCP issues.Wrong answer — click to see why▾
Why this is wrong here
Portfast is actually recommended for access ports to avoid delays; removing it would cause longer convergence and not fix DHCP.
✗The service-policy input QOS_POLICY is blocking DHCP packets.Wrong answer — click to see why▾
Why this is wrong here
Unless specifically configured to drop DHCP, the policy would not prevent IP address assignment.
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 is missing or the VLAN does not exist; ensure VLAN 10 is created and allowed on the trunk. — The port is configured with both an access VLAN (10) and a voice VLAN (20). The switchport voice vlan command is used to separate voice traffic into a dedicated VLAN, but the phone must be able to communicate on the access VLAN to obtain an IP address for the PC. The problem is that the access VLAN 10 is not present on the switch or is not allowed on the trunk to the DHCP server. The correct answer is to ensure VLAN 10 exists and is allowed on the uplink. The other options are incorrect because the voice VLAN is correctly configured, PortFast and QoS policies do not affect DHCP, and the native VLAN mismatch would cause different symptoms.
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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