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Catalyst 3750-X and 3560-X Switch Command Reference
OL-29704-01
Chapter 2 Catalyst 3750-X and 3560-X Switch Cisco IOS Commands
auto qos voip
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 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 2-10 and
Table 2-11. The policing is applied to those traffic matching the policy-map classification before the
switch enables the trust boundary feature.
• 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 2-10 and Table 2-11.
• When you enter the auto qos voip trust interface configuration command on a port connected to the
network interior, 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 2-10 and Table 2-11.
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.
After auto-QoS is enabled, do not modify a policy map or aggregate policer that includes AutoQoS in its
name. If you need to modify the policy map or aggregate policer, make a copy of it, and change the
copied policy map or policer. To use the new policy map instead of the generated one, remove the
generated policy map from the interface, and apply the new policy map.
To display the QoS configuration that is automatically generated when auto-QoS is enabled, enable
debugging before you enable auto-QoS. Use the debug auto qos privileged EXEC command to enable
auto-QoS debugging. For more information, see the debug auto qos command.
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