Name: Cisco Catalyst 3750
Brand: Cisco
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26-31

Catalyst 3750 Metro Switch Software Configuration Guide

78-15870-01

Chapter 26 Configuring QoS

Configuring Auto-QoS

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. 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 queues and the egress

queue-set on the port according to the settings in Table 26-3 and Table 26-4.

• 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 queues and the egress queue-set on the port

according to the settings in Table 26-3 and Table 26-4.

For information about the trusted boundary feature, see the “Configuring a Trusted Boundary to

Ensure Port Security” section on page 26-46.

When you enable auto-QoS by using the auto qos voip cisco-phone or the auto qos voip trust interface

configuration command, the switch automatically generates a QoS configuration based on the traffic

type and the ingress packet label and applies the commands listed in Table 26-5 to the port.

Note On an ES port, the srr-queue bandwidth shape interface configuration command is not part of the

generated auto qos voip command list.

Table 26-5 Generated Auto-QoS Configuration

Description Automatically Generated Command

The switch automatically enables standard QoS and configures

the CoS-to-DSCP map (maps CoS values in inbound packets to

a DSCP value).

Switch(config)# mls qos

Switch(config)# mls qos map cos-dscp 0 8 16 26 32 46

48 56

The switch automatically maps CoS values to an ingress queue

and to a threshold ID.

Switch(config)# no mls qos srr-queue input cos-map

Switch(config)# mls qos srr-queue input cos-map

queue 1 threshold 3 0

Switch(config)# mls qos srr-queue input cos-map

queue 1 threshold 2 1

Switch(config)# mls qos srr-queue input cos-map

queue 2 threshold 1 2

Switch(config)# mls qos srr-queue input cos-map

queue 2 threshold 2 4 6 7

Switch(config)# mls qos srr-queue input cos-map

queue 2 threshold 3 3 5

The switch automatically maps CoS values to an egress queue

in the queue-set and to a threshold ID.

Switch(config)# no mls qos srr-queue output cos-map