Prioritizing voice VLAN QoS (Optional)

Without configuring the switch to prioritize voice VLAN traffic, one of the following conditions applies:

  • If the ports in a voice VLAN are not tagged members, the switch forwards all traffic on that VLAN at "normal" priority.

  • If the ports in a voice VLAN are tagged members, then the switch forwards all traffic on that VLAN at whatever priority the traffic has when received inbound on the switch.

Using the switch's QoS VLAN-ID (VID) priority option, you can change the priority of voice VLAN traffic moving through the switch. If all port memberships on the voice VLAN are tagged, the priority level you set for voice VLAN traffic is carried to the next device. With all ports on the voice VLAN configured as tagged members, you can enforce a QoS priority policy moving through the switch and through your network.

Syntax: 

vlan <vid> qos priority <0-7>

The qos priority default setting is 0 (normal), with 1 as the lowest priority and 7 as the highest priority.

If you configure a voice VLAN with a VID of 10 and want the highest priority for all traffic on this VLAN, execute the following commands: 

switch(config)# vlan 10 qos priority 4
switch(config)# write memory

You also have the option of resetting the DSCP (DiffServe Codepoint) on tagged voice VLAN traffic moving through the switch. For more information, see Quality of Service (QoS): Managing bandwidth effectively.

If all port memberships on the voice VLAN are tagged:

  • The priority level set for voice VLAN traffic is carried to the next device.

  • You can enforce a QoS priority policy moving through the switch and network.

For more information, see Using voice VLANs.