350-401 Infrastructure Practice Question
A network administrator is configuring a Cisco Catalyst switch to assign a voice VLAN to IP phones. The phones will tag voice traffic with VLAN 200, and data traffic from attached PCs should be untagged in VLAN 10. Which interface configuration correctly implements this?
⚠ Common exam trap
Test-takers frequently confuse voice VLAN configuration with trunk configuration; voice VLAN is enabled on an access port, not by making the port a trunk.
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 access, switchport access vlan 10, switchport voice vlan 200
The correct configuration uses an access port for data VLAN 10 and the switchport voice vlan command for voice VLAN 200. This enables the switch to send CDP/LLDP-MED instructions to the phone to tag voice traffic in VLAN 200 while data remains untagged in VLAN 10. It is the standard Cisco IP telephony deployment.
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, switchport trunk native vlan 10, switchport trunk allowed vlan 200
Why it's wrong here
Configuring the port as a trunk with native VLAN 10 and allowed VLAN 200 would tag data traffic in VLAN 10 (if not native) but the native VLAN is untagged. However, this does not automatically assign voice VLAN 200 to the phone; the phone would need to be configured for trunking. The switchport voice vlan command is the correct method for voice VLAN assignment, and this configuration lacks it.
- ✗
Switchport mode trunk, switchport trunk encapsulation dot1q, switchport trunk native vlan 200
Why it's wrong here
This makes the port a trunk with native VLAN 200, which would send untagged traffic in VLAN 200, not VLAN 10. It also does not specify allowed VLANs or a voice VLAN, so voice traffic would not be properly tagged. The requirement is for an access port with voice VLAN, not a trunk with native VLAN 200.
- ✗
Switchport mode access, switchport access vlan 200, switchport voice vlan 10
Why it's wrong here
This reverses the VLAN assignments: data traffic would be in VLAN 200 and voice in VLAN 10. The scenario requires data VLAN 10 and voice VLAN 200, so this configuration is incorrect. Additionally, the voice VLAN should carry tagged traffic, and the access VLAN is for untagged data, so the roles are swapped.
- ✓
Switchport mode access, switchport access vlan 10, switchport voice vlan 200
Why this is correct
This configuration sets the port as an access port for data VLAN 10 and enables voice VLAN 200 for tagged voice traffic. The switchport voice vlan command instructs the switch to use 802.1Q tagging for voice frames while data frames remain untagged. This is the standard Cisco configuration for connecting an IP phone with a PC attached, meeting the requirements.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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