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.
Exhibit
SW1# show running-config interface gigabitEthernet 1/0/1
Building configuration...
Current configuration : 150 bytes
!
interface GigabitEthernet1/0/1
switchport mode access
switchport access vlan 10
no shutdown
end
SW1# show interfaces gigabitEthernet 1/0/1 switchport
Name: Gi1/0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 10 (VLAN0010)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Refer to the exhibit. A network administrator connects an IP phone to interface GigabitEthernet1/0/1 on a Cisco Catalyst switch. The PC connected through the phone works normally on the data VLAN, but the phone cannot obtain an IP address and fails to register with the call server. Which action will resolve the problem?
SW1# show running-config interface gigabitEthernet 1/0/1
Building configuration...
Current configuration : 150 bytes
!
interface GigabitEthernet1/0/1
switchport mode access
switchport access vlan 10
no shutdown
end
SW1# show interfaces gigabitEthernet 1/0/1 switchport
Name: Gi1/0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 10 (VLAN0010)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
A
Configure 'switchport trunk allowed vlan 10,20' on interface Gi1/0/1 and change the switchport mode to trunk.
Why wrong: Changing to trunk mode would force both PC and phone to trunk, likely breaking PC connectivity.
B
Add 'switchport voice vlan 20' on interface GigabitEthernet1/0/1.
This command enables the access port to support a voice VLAN, telling the phone to tag voice frames with VLAN 20 while leaving data in VLAN 10.
C
Issue 'switchport access vlan 20' and 'switchport voice vlan 10' on interface Gi1/0/1.
Why wrong: This swaps the VLAN assignments: voice traffic would be sent untagged or in VLAN 10, and the phone would try to get an IP in the wrong subnet.
D
Enable 'switchport port-security mac-address sticky' on the interface and manually add the phone’s MAC address to the access VLAN.
Why wrong: Port security limits MAC addresses but does not influence VLAN assignment or voice VLAN discovery.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add 'switchport voice vlan 20' on interface GigabitEthernet1/0/1.
The PC works on the data VLAN, but the phone cannot obtain an IP address, indicating the phone is not receiving the correct VLAN assignment. The phone should be placed in the voice VLAN (VLAN 20) using the 'switchport voice vlan 20' command, which allows the switch to tag the phone's traffic with VLAN 20 via CDP/LLDP, enabling it to get an IP from the voice VLAN DHCP server.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Configure 'switchport trunk allowed vlan 10,20' on interface Gi1/0/1 and change the switchport mode to trunk.
Why it's wrong here
Changing to trunk mode would force both PC and phone to trunk, likely breaking PC connectivity.
✓
Add 'switchport voice vlan 20' on interface GigabitEthernet1/0/1.
Why this is correct
This command enables the access port to support a voice VLAN, telling the phone to tag voice frames with VLAN 20 while leaving data in VLAN 10.
Related concept
Read the scenario before looking for a memorised answer.
✗
Issue 'switchport access vlan 20' and 'switchport voice vlan 10' on interface Gi1/0/1.
Why it's wrong here
This swaps the VLAN assignments: voice traffic would be sent untagged or in VLAN 10, and the phone would try to get an IP in the wrong subnet.
✗
Enable 'switchport port-security mac-address sticky' on the interface and manually add the phone’s MAC address to the access VLAN.
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.
✓Add 'switchport voice vlan 20' on interface GigabitEthernet1/0/1.Correct answer▾
Why this is correct
This command enables the access port to support a voice VLAN, telling the phone to tag voice frames with VLAN 20 while leaving data in VLAN 10.
✗Configure 'switchport trunk allowed vlan 10,20' on interface Gi1/0/1 and change the switchport mode to trunk.Wrong answer — click to see why▾
Why this is wrong here
A trunk port does not provide the voice VLAN advertisement mechanism to the phone; the PC would need to send tagged frames, which typical endpoint NICs do not do.
✗Issue 'switchport access vlan 20' and 'switchport voice vlan 10' on interface Gi1/0/1.Wrong answer — click to see why▾
Why this is wrong here
The phone requires access to VLAN 20 for voice services, and the PC must remain in VLAN 10 for data; this configuration does the opposite, failing to meet the requirement.
✗Enable 'switchport port-security mac-address sticky' on the interface and manually add the phone’s MAC address to the access VLAN.Wrong answer — click to see why▾
Why this is wrong here
The phone still cannot learn the voice VLAN; port security does not provide a DHCP address or make the switch advertise VLAN 20 to the phone.
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: answer the scenario, not the keyword
Cisco often tests the distinction between 'switchport access vlan' (for data) and 'switchport voice vlan' (for voice), and the trap here is that candidates may confuse which VLAN is assigned to which device, or incorrectly think trunking is required for a phone connection.
Detailed technical explanation
How to think about this question
When a Cisco IP phone is connected to a switchport configured with 'switchport voice vlan', the switch uses CDP (or LLDP) to inform the phone of the voice VLAN ID. The phone then tags its own traffic with that VLAN, while the PC's traffic remains untagged in the native (access) VLAN. This allows both devices to share a single physical link while maintaining separate Layer 2 domains, and the phone obtains an IP address from the DHCP server in the voice VLAN.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Switching and Network Access — This question tests Switching and Network Access — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add 'switchport voice vlan 20' on interface GigabitEthernet1/0/1. — The PC works on the data VLAN, but the phone cannot obtain an IP address, indicating the phone is not receiving the correct VLAN assignment. The phone should be placed in the voice VLAN (VLAN 20) using the 'switchport voice vlan 20' command, which allows the switch to tag the phone's traffic with VLAN 20 via CDP/LLDP, enabling it to get an IP from the voice VLAN DHCP server.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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