Cisco Catalyst 3550 Series User Manual

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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Configuring Auto-QoS
Generated Auto-QoS Configuration
By default, auto-QoS is disabled on all interfaces.
When auto-QoS is enabled, it uses the ingress packet label to categorize traffic and to configure the
egress queues as shown in Table 29-1.
Table 29-2 shows the generated auto-QoS configuration for the egress queues.
When you enable the auto-QoS feature on the first interface, these automatic actions occur:
• QoS is globally enabled (mls qos global configuration command).
• When you enter the auto qos voip trust interface configuration command, the ingress classification
on the interface is set to trust the QoS label received in the packet, and the egress queues on the
interface are reconfigured (see Table 29-2).
• When you enter the auto qos voip cisco-phone interface configuration command, the trusted
boundary feature is enabled. It 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 egress queues on the
interface are also reconfigured (see Table 29-2).
Table 29-1 Traffic Types, Ingress Packet Labels, Assigned Packet Labels, and Egress Queues
VoIP Data
Traffic Only
From Cisco IP
Phones
VoIP Control
Traffic Only
From Cisco IP
Phones
Routing Protocol
Traffic
STP BPDU
1
Traffic
1. BPDU = bridge protocol data unit.
All Other
Traffic
Ingress DSCP 46 26 –––
Ingress CoS 5 3 6 7 –
DiffServ EF AF31 –––
Assigned DSCP 46 26 48 56 0
Assigned CoS 5 3 6 7 0
CoS-to-Queue
Map
5 3, 6, 7 0, 1, 2, 4
Egress Queue Expedite
queue
80% WRR 20% WRR
Table 29-2 Auto-QoS Configuration for the Egress Queues
Egress Queue
Queue
Number
CoS-to-Queue
Map
Queue
Weight
Queue Size for
Gigabit-Capable
Ports
Queue Size (in
packets) for 10/100
Ethernet Ports
Expedite 4 5 –– 26
80% WRR 3 3, 6, 7 80% 20% 65
20% WRR 1 0, 1, 2, 4 20% 80% 170

Cisco Catalyst 3550 Series Specifications

General

Brand	Cisco
Model	Catalyst 3550 Series
Category	Network Router
Language	English