Cisco 2950 - Catalyst Switch Configuration Manual page 571

Chapter 30 Configuring QoS
When you enable the auto-QoS feature on the first interface, these automatic actions occur:
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When you enable auto-QoS by using the auto qos voip cisco-phone, the auto qos voip cisco-softphone,
or the auto qos voip trust interface configuration command, the switch automatically generates a QoS
configuration based on the traffic type and ingress packet label and applies the commands listed in
Table 30-4
Table 30-4 Generated Auto-QoS Configuration
Description
The switch automatically enables standard QoS and configures
the CoS-to-DSCP map (maps CoS values in incoming packets
to a DSCP value) as shown in
If you entered the auto qos voip trust command, the switch
automatically sets the ingress classification on the interface to
trust the CoS value received in the packet.
If you entered the auto qos voip cisco-phone command, the
switch automatically enables the trusted boundary feature,
which uses the CDP to detect the presence or absence of a
Cisco IP Phone.
78-11380-10
When you enter the auto qos voip cisco-phone interface configuration command on a port at the
edge of a 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 interface is set
to trust the QoS label received in the packet. When a Cisco IP Phone is absent, the ingress
classification is set to not trust the QoS label in the packet. The switch configures egress queues on
the port according to the settings in
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 egress queues on the port according to the settings in
Table 30-3.
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 in ingress packets (the assumption is that
traffic has already been classified by other edge devices). The switch configures egress queues on
the port according to the settings in
For information about the trusted boundary feature, see the
on page 30-23.
to the interface.
Table 30-2 on page 30-10.
Table 30-3.
Table 30-3.
Automatically Generated QoS Command Equivalent
Switch(config)# mls qos map cos-dscp 0 8 16 26 32 46
48 56
Switch(config-if)# mls qos trust cos
Switch(config-if)# mls qos trust device cisco-phone
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
Configuring Auto-QoS
"Configuring Trusted Boundary" section
30-11