notes: Voice VLAN

Voice VLAN (VVLAN)
- Most Cisco phones have a built-in 3-port switch and is able to distinguish the phone and the PC using different VLANs and optionally 802.1p COS.
- Voice config is communicated via CDP to the IP phone.

3 different connecting options:

1. Separate DATA VLAN / VOICE VLAN.
- VOIP frames are tagged with COS 5.
- Connection between switch and IP phone is a 802.1q trunk with native VLAN equal to data VLAN.

config set:

interface FastEthernet0/2
switchport access vlan 146
switchport voice vlan 600
spanning-tree portfast
!
interface FastEthernet0/4
switchport trunk encapsulation dot1q
switchport trunk native vlan 146
switchport trunk allowed vlan 146,600
switchport mode trunk
switchport voice vlan 600
spanning-tree portfast trunk
spanning-tree bpdufilter enable

Note that as soon as the switchport voice vlan command is applied to the
port, the spanning-tree portfast feature is automatically enabled.


2. Single VLAN for both VOICE and DATA
- Frames are not tagged, thus the phone merely acts as a switch.
- Connection between switch and IP phone is configured as a ACCESS link.

if no "switchport voice vlan" configured, then option 2 automatically applies.

3. Single VLAN for DATA and VOICE but with COS 5 marking

- ATA traffic is marked as COS 0 within a 802.1q header.
- VOICE traffic is marked as COS 5 within the 802.1q header.
- COS zero will be accepted as the access VLAN.

config set:

interface FastEthernet0/6
switchport access vlan 146
switchport voice vlan dot1p