CCNA Network Infrastructure and Connectivity Practice Question
A network administrator is configuring a Cisco switch to support a new voice VLAN. The design requires that IP phones and PCs share the same switch port, with voice traffic tagged and data traffic untagged. Which two commands are required on the switch port to support this configuration? (Choose two.)
⚠ Common exam trap
The trap here is thinking the port must be a trunk to carry both voice and data, when in fact a voice VLAN configuration uses access mode with a special voice VLAN designation.
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 voice vlan 50
To support an IP phone and PC on the same switch port, the port must be in access mode for the data VLAN and have a voice VLAN configured. The switchport mode access command ensures untagged data traffic, while switchport voice vlan 50 instructs the phone to tag voice traffic with VLAN 50. Together, these commands enable the required separation of voice and data traffic.
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 voice vlan 50
Why this is correct
The switchport voice vlan 50 command configures the port to use VLAN 50 for voice traffic. The switch will send CDP or LLDP-MED messages to the IP phone, instructing it to tag voice frames with VLAN 50. This allows the phone to separate voice and data traffic, with voice frames tagged and data frames untagged, meeting the design requirement.
- ✗
switchport mode trunk
Why it's wrong here
Configuring the port as a trunk would cause the data traffic from the PC to be tagged as well, which is not desired. In a voice VLAN configuration, the port remains in access mode for the data VLAN, and only voice traffic is tagged. Using trunk mode would require the PC to understand 802.1Q tagging, which typical PCs do not, and would not meet the requirement of untagged data traffic.
- ✗
switchport access vlan 10
Why it's wrong here
The switchport access vlan 10 command assigns the port to VLAN 10 for data traffic. While this may be part of the configuration, it is not strictly required to enable voice VLAN functionality. The question asks for commands required to support the voice VLAN configuration. The essential commands are setting the port to access mode and configuring the voice VLAN. Assigning a specific data VLAN is optional and depends on the design.
- ✗
switchport trunk encapsulation dot1q
Why it's wrong here
The switchport trunk encapsulation dot1q command is used to set the encapsulation type on a trunk port. Since the port is configured as an access port with a voice VLAN, this command is not applicable. It is used on trunk interfaces, not on access ports with voice VLANs. Therefore, it is not required for this configuration.
- ✓
switchport mode access
Why this is correct
The switchport mode access command places the port in access mode, which is necessary for the data VLAN (untagged traffic). When combined with the voice VLAN command, the port can carry untagged data traffic for the PC and tagged voice traffic for the IP phone. This is the standard configuration for a port supporting both a PC and an IP phone.
Visual reference
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Related to this question
Learn chapter
Exam Trap: NAT Configuration Errors
Key term
Data VLAN
A Data VLAN is a virtual local area network configured on a switch to carry user-generated traffic, separating it from management, voice, or other types of network traffic.
Key term
VLAN
A VLAN logically segments a physical network into isolated broadcast domains without requiring separate physical switches.
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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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