Cisco Certified Support Technician (CCST) NetworkingNetwork AccessMedium
A network technician is configuring a new switch for a small business. The business needs to connect several IP phones and desktop computers to the same switch ports. To ensure voice quality, the IP phones should be placed in a separate VLAN (VLAN 10 for voice) and assigned a higher Quality of Service (QoS) priority, while the desktop computers should be in the default data VLAN (VLAN 1). Which feature on the switch port simplifies this configuration and ensures proper VLAN assignment for both device types?
- ADHCP Snooping
- BPort Security
- CSTP PortFast
- DVoice VLAN
Show answer & explanationAnswer & explanation
Correct answer: D. Voice VLAN
The Voice VLAN feature allows a switch port to carry traffic for two VLANs: a data VLAN and a voice VLAN. It automatically configures QoS for the voice VLAN and assigns the IP phone to the correct voice VLAN, while the connected PC remains in the data VLAN.
Why the other options are wrong
- A. DHCP Snooping is a security feature that prevents rogue DHCP servers, unrelated to dual VLAN assignment on a port.
- B. Port Security controls which MAC addresses are allowed on a port, not VLAN assignment for multiple devices.
- C. STP PortFast speeds up port transition to the forwarding state, unrelated to VLAN assignment or QoS for voice.
Voice VLAN
A Cisco switch feature that allows a single access port to carry traffic for both an IP phone (in a dedicated voice VLAN with QoS) and a connected PC (in a data VLAN).
- Automatically configures QoS for voice traffic.
- Simplifies deployment of IP phones.
- Requires the IP phone to support discovery protocols like CDP or LLDP-MED.
Memory trick: Voice VLAN: one port, two hats for phone and PC.