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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter29 Configuring QoS
Configuring Auto-QoS
The input mutation causes the DSCP to be rewritten depending on the new value of DSCP chosen.
The set action in a policy map also causes the DSCP to be rewritten.
Configuring Auto-QoS
You can use the auto-QoS feature to simplify the deployment of existing QoS features. Auto-QoS makes
assumptions about the network design, and as a result, the switch can prioritize different traffic flows
and appropriately use the ingress and egress queues instead of using the default QoS behavior. (The
default is that QoS is disabled. The switch then offers best-effort service to each packet, regardless of
the packet contents or size, and sends it from a single queue.)
When you enable auto-QoS, it automatically classifies traffic based on the traffic type and ingress packet
label. The switch uses the resulting classification to choose the appr opriate egress queue.
You use auto-QoS commands to identify ports connected to Cisco IP Phones and to devices runni ng the
Cisco SoftPhone application. You also use the commands to identify ports that receive trusted traffic
through an uplink. Auto-QoS then performs these functions:
Detects the presence or absence of Cisco IP Phones
Configures QoS classification
Configures egress queues
These sections contain this configuration information:
Generated Auto-QoS Configuration, page 29-19
Effects of Auto-QoS on the Configuration, page 29-24
Auto-QoS Configuration Guidelines, page 29-24
Enabling Auto-QoS for VoIP, page 29-25
Auto-QoS Configuration Example, page 29-26

Generated Auto-QoS Configuration

By default, auto-QoS is disabled on all ports.
When auto-QoS is enabled, it uses the ingress packet label to categorize traffic, to assign packet labels,
and to configure the ingress and egress queues as shown in Table 29-2.
Table29-2 Traffic Types, Packet Labels, and Queues
VoIP1 Data
Traffic
1. VoIP = voice over IP
VoIP Control
Traffic
Routing Protocol
Traffic
STP BPDU
Traffic
Real-Time
Video Traffic All Other Traffic
DSCP 46 24, 26 48 56 34
CoS 5 3 6 7 4
CoS-to-Ingress
Queue Map
2, 3, 4, 5, 6, 7 (queue 2) 0, 1 (queue 1)
CoS-to-Egress
Queue Map
5 (queue 1) 3, 6, 7 (queue 2) 4 (queue 3) 2 (queue 3) 0, 1
(queue 4)