Cisco Catalyst 3750-E Series, Software Configuration Manual

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Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 37 Configuring QoS
Configuring Auto-QoS
Generated Auto-QoS Configuration
By default, auto-QoS is disabled on all ports. Packets are not modified--the CoS, DSCP and IP
precedence values in the packet are not changed.
When you enable the auto-QoS feature on the first port of the interface:
• Ingress packet label is used to categorize traffic, to assign packet labels, and to configure the ingress
and egress queues.
•
QoS is globally enabled ( mls qos global configuration command), and other global configuration
commands are automatically generated. (See Table 37-5 .)
• Switch enables the trusted boundary feature and uses the Cisco Discovery Protocol (CDP) to detect
the presence of a supported device.
•
Policing is used to determine whether a packet is in or out of profile and specifies the action on the
packet.
VOIP Device Specifics
•
When you enter the auto qos voip cisco-phone command on a port at the network edge connected
to a Cisco IP Phone, the switch enables the trusted boundary feature. If the packet does not have a
DSCP value of 24, 26, or 46 or is out of profile, the switch changes the DSCP value to 0. When there
is no Cisco IP Phone, the ingress classification is set to not trust the QoS label in the packet. The
policing is applied to the traffic matching the policy-map classification before the switch enables the
trust boundary feature.
•
When you enter the auto qos voip cisco-softphone interface configuration command on a port at
the network edge that is connected to a device running the Cisco SoftPhone, the switch uses policing
to determine whether a packet is in or out of profile and to specify the action on the packet. If the
packet does not have a DSCP value of 24, 26, or 46 or is out of profile, the switch changes the DSCP
value to 0.
•
When you enter the auto qos voip trust interface configuration command on a port connected to the
network interior, 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 ingress and egress queues on the port according to the settings in Table 37-3 and
Table 37-4 .
Table 37-2 Traffic Types, Packet Labels, and Queues
VoIP
1
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 3 –
CoS-to-Ingress
Queue Map 4, 5 (queue 2) 0, 1, 2, 3, 6, 7(queue 1)
CoS-to-Egress
Queue Map 4, 5
(queue 1)
2, 3, 6, 7 (queue 2) 0 (queue 3) 2 (queue 3) 0, 1
(queue 4)