Specifications

27-10
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 27 Configuring QoS
Configuring Auto-QoS
You use auto-QoS commands to identify ports connected to Cisco IP Phones and to identify ports that
receive trusted voice over IP (VoIP) traffic through an uplink. Auto-QoS then performs these functions:
• Detects the presence or absence of IP phones
• Configures QoS classification
• Configures egress queues
These sections describe how to configure auto-QoS on your switch:
• Generated Auto-QoS Configuration, page 27-10
• Effects of Auto-QoS on the Configuration, page 27-12
• Configuration Guidelines, page 27-12
• Enabling Auto-QoS for VoIP, page 27-12
Generated Auto-QoS Configuration
When auto-QoS is enabled, it uses the ingress packet label to classify traffic and to configure the egress
queues as described in Table 27-2.
Table 27-3 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:
Table 27-2 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 –
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 27-3 Auto-QoS Configuration for the Egress Queues
Egress Queue Queue Number CoS-to-Queue Map Queue Weight
Expedite 4 5 –
80% WRR 3 3, 6, 7 80%
20% WRR 1 0, 1, 2, 4 20%