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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring QoS
Configuring Auto-QoS
• Depending on the QoS label assigned to a frame and the mutation chosen, the DSCP and CoS values
of the frame are rewritten. If you do not configure the mutation map and if you configure the port to
trust the DSCP of the incoming frame, the DSCP value in the frame is not changed, but the CoS is
rewritten according to the DSCP-to-CoS map. If you configure the port to trust the CoS of the
incoming frame and it is an IP packet, the CoS value in the frame is not changed, but the DSCP might
be changed according to the CoS-to-DSCP map.
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 QoS features. Auto-QoS determines the
network design and enables QoS configurations so that the switch can prioritize different traffic flows.
It uses the ingress and egress queues instead of using the default (disabled) QoS behavior. The switch
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 classification results to choose the appropriate egress queue.
Auto-QoS supports IPv4 and IPv6 traffic when you configure the dual IPv4 and IPv6 SDM template with
the sdm prefer dual ipv4-and-ipv6 global configuration command.
Note IPv6 Auto-QoS is not supported on switches running the LAN base feature set.
You can use auto-QoS commands to identify ports connected to these Cisco devices:
• Cisco IP Phones
• Devices running the Cisco SoftPhone application
• Cisco TelePresence
• Cisco IP Camera
• Cisco digital media player
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 auto-QoS devices through conditional trusted interfaces.
• Configures QoS classification
• Configures egress queues
These sections contain this configuration information:
• Generated Auto-QoS Configuration, page 1-24
• Effects of Auto-QoS on the Configuration, page 1-33
• Auto-QoS Configuration Guidelines, page 1-33
• Enabling Auto-QoS, page 1-34
• Troubleshooting Auto QoS Commands, page 1-35
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