» Voice VLAN

By | September 24, 2012

Here you will find answers to Voice VLAN Questions

Question 1

What is the difference between voice VLAN and native VLAN?

A. Voice VLAN uses tagged 802.1Q frames whereas native VLAN uses 802.1P frames.
B. Voice VLAN uses untagged frames whereas native VLAN uses 802.1Q frames.
C. Voice VLAN uses tagged 802.1Q frames whereas native VLAN uses untagged frames.
D. Voice VLAN uses untagged frames only when no PCs are connected behind the phones
whereas native VLAN always uses untagged frames.

Answer: C


For 802.1Q trunking, one VLAN is not tagged. This VLAN is called native VLAN. The native VLAN is used for untagged traffic when the port is in 802.1Q trunking mode. For Voice VLAN, we need to specific a VLAN to use for voice traffic.

Question 2

Which protocol is used to inform the IP phone of its voice VLAN ID?

A. Cisco keepalives
B. Cisco Discovery Protocol
C. Cisco Spanning Tree Protocol
D. Cisco VLAN Discovery Protocol

Answer: B


Cisco IP phones will be able to receive voice VLAN configuration via CDP. Once it has received the voice VLAN idr, the IP phone will begin tagging its own packets. Non-Cisco IP phones will not be able to understand CDP packets.

Question 3

Which command is used to assign voice VLAN 110 on a Cisco IOS switch?

A. switchport access vlan 110
B. switchport access voice vlan 110
C. switchport voice vlan 110
D. switchport voice access vlan 110

Answer: C


The syntax of this command is “switchport voice vlan {vlan-id | dot1p | untagged | none}”