Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureMedium
A network engineer needs to configure a Cisco Catalyst 9300 switch to automatically detect and assign a specific VLAN for IP phones connected to access ports, ensuring they receive the correct voice QoS and DHCP options. Which feature enables this automatic VLAN assignment for IP phones?
- AVoice VLAN
- B802.1X Authentication
- CPort Security
- DDHCP Snooping
Show answer & explanationAnswer & explanation
Correct answer: A. Voice VLAN
The Voice VLAN feature allows a Cisco switch port to carry both data and voice traffic, automatically assigning IP phones to a dedicated voice VLAN based on their Organizational Unique Identifier (OUI) or CDP/LLDP discovery. This ensures proper QoS and simplified management for voice devices.
Why the other options are wrong
- B. 802.1X Authentication provides port-based network access control, authenticating devices before allowing network access, not automatically assigning a voice VLAN.
- C. Port Security restricts devices by MAC address on a port to prevent unauthorized access, not for automatic voice VLAN assignment.
- D. DHCP Snooping is a security feature that filters untrusted DHCP messages, preventing rogue DHCP servers, not for voice VLAN assignment.
Voice VLAN
A Cisco switch feature that creates a dedicated VLAN for IP phone traffic, allowing both voice and data devices to share the same physical access port while maintaining separate logical networks and QoS policies.
- Automatically assigns IP phones to a specific VLAN.
- Ensures proper QoS for voice traffic.
- Uses CDP/LLDP or OUI for phone detection.
Memory trick: Voice VLAN: Virtual Lane for Vocal Connections