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Catalyst 3750 Switch Command Reference
OL-8552-07
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
auto qos voip
Note The switch applies the auto-QoS-generated commands as if the commands were entered from the
command-line interface (CLI). An existing user configuration can cause the application of the generated
commands to fail or to be overridden by the generated commands. These actions occur without warning.
If all the generated commands are successfully applied, any user-entered configuration that was not
overridden remains in the running configuration. Any user-entered configuration that was overridden can
be retrieved by reloading the switch without saving the current configuration to memory. If the generated
commands fail to be applied, the previous running configuration is restored.
If this is the first port on which you have enabled auto-QoS, the auto-QoS-generated global
configuration commands are executed followed by the interface configuration commands. If you enable
auto-QoS on another port, only the auto-QoS-generated interface configuration commands for that port
are executed.
When you enable the auto-QoS feature on the first port, these automatic actions occur:
• QoS is globally enabled (mls qos global configuration command), and other global configuration
commands are added.
• When you enter the auto qos voip cisco-phone interface configuration command on a port at the
edge of the network that is connected to a Cisco IP Phone, the switch enables the trusted boundary
feature. The switch uses the Cisco Discovery Protocol (CDP) to detect the presence or absence of a
Cisco IP Phone. When a Cisco IP Phone is detected, the ingress classification on the port is set to
trust the QoS label received in the packet. The switch also uses policing to determine whether a
packet is in or out of profile and to specify the action on the packet. If the packet does not have a
DSCP value of 24, 26, or 46 or is out of profile, the switch changes the DSCP value to 0. When a
Cisco IP Phone is absent, the ingress classification is set to not trust the QoS label in the packet. The
switch configures ingress and egress queues on the port according to the settings in
Table 2-2 and
Table 2-3. The policing is applied to traffic matching the policy-map classification before the switch
enables the trust boundary feature.
If the switch port was configured by using the auto qos voip cisco-phone interface configuration
command in Cisco IOS Release 12.2(37)SE or earlier, the auto-QoS generated commands new to
Cisco IOS Release 12.2(40)SE are not applied to the port. To have these commands automatically
applied, you must remove and then reapply the configuration to the port.
• When you enter the auto qos voip cisco-softphone interface configuration command on a port at
the edge of the network that is connected to a device running the Cisco SoftPhone, the switch uses
policing to decide whether a packet is in or out of profile and to specify the action on the packet. If
the packet does not have a DSCP value of 24, 26, or 46 or is out of profile, the switch changes the
DSCP value to 0. The switch configures ingress and egress queues on the port according to the
settings in
Table 2-2 and Table 2-3.
• When you enter the auto qos voip trust interface configuration command on a port connected to
the interior of the network, the switch trusts the CoS value for nonrouted ports or the DSCP value
for routed ports in ingress packets (the assumption is that traffic has already been classified by other
edge devices). The switch configures the ingress and egress queues on the port according to the
settings in
Table 2-2 and Table 2-3.
You can enable auto-QoS on static, dynamic-access, and voice VLAN access, and trunk ports. When
enabling auto-QoS with a Cisco IP Phone on a routed port, you must assign a static IP address to the
IP
phone.
Note When a device running Cisco SoftPhone is connected to a switch or routed port, the switch supports only
one Cisco SoftPhone application per port.
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