Configuring VoIP Support on a Switch

Manual Configuration

To associate a voice VLAN with a switch port, use the following:

Switch(config-if)#switchport voice vlan vlan-ID


To configure an IOS switch to trust the markings on traffic entering an interface, use the following:

Switch(config-if)#mls qos trust {dscp | cos}


To configure the switch to trust the traffic markings only if a Cisco
phone is connected, use the following:

Switch(config-if)#mls qos trust device cisco-phone


To set a COS value for frames coming from a PC attached to the
phone, use the following:

Switch(config-if)#switchport priority extend cos cos-value


To verify the interface parameters, use the following:

Switch(config-if)#show interfaces interface switchport


To verify the QoS parameters on an interface, use the following:

Switch(config-if)#show mls qos interface interface


Using AutoQoS

When AutoQoS is enabled, the switch configures its interfaces based on a best-practices template. AutoQoS has the following benefits:

• Automatic discovery and classification of network applications.

• Creates QoS policies for those applications.

• Configures the switch to support Cisco IP phones as well as network applications. Manual configuration can be done afterward, also.

• Sets up SNMP traps for network reporting.

• Configures consistently across your network when used on all routers and switches.

CDP must be enabled for AutoQoS to function properly with Cisco IP phones.

AutoQoS commands for switches running the Catalyst OS are listed in Table 7-2.


AutoQoS commands for switches running Native IOS are shown in Table 7-3.