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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Configuring Auto-QoS
Table 29-3 lists the generated auto-QoS configuration for the egress queues.
When you enable the auto-QoS feature on the first interface, these automatic actions occur:
• 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 Table 29-3.
• 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 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. The switch configures egress queues on the port according to the settings in
Table 29-3.
• 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 Table 29-3.
For information about the trusted boundary feature, see the “Configuring Trusted Boundary” section
on page 29-21.
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 29-4 to the interface.
1. VoIP = voice over IP
2. BPDU = bridge protocol data unit
Tab l e 29-3 Auto-QoS Configuration for the Egress Queues
Egress Queue Queue Number CoS-to-Queue Map Queue Weight
1% WRR 4 5 1 percent
70% WRR 33, 6, 7 70 percent
20% WRR 22, 4 20 percent
10% WRR 10,1 10 percent
Tab l e 29-4 Generated Auto-QoS Configuration
Description Automatically Generated QoS Command Equivalent
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 Table 29-2 on page 29-9.
Switch(config)# mls qos map cos-dscp 0 8 16 26 32 46
48 56
If you entered the auto qos voip trust command, the switch
automatically sets the ingress classification on the interface to
trust the CoS value in the packet.
Switch(config-if)# mls qos trust cos