Specifications

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 27 Configuring QoS
Configuring Auto-QoS
• 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 27-3).
• 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 reconfigured (see Table 27-3).
For information about the trusted boundary feature, see the “Configuring Trusted Boundary” section
on page 27-20.
When you enable auto-QoS by using the auto qos voip cisco-phone or the auto qos voip trust interface
configuration command, the switch automatically generates a QoS configuration based on the traffic
type and ingress packet label and applies the commands listed in Table 27-4 to the interface.
Table 27-4 Generated Auto-QoS Configuration Command Equivalents
Description Automatically Generated QoS Command Equivalent
The switch automatically enables standard QoS and configures
the CoS-to-DSCP map (maps CoS values in incoming packets
to a DSCP value) as shown in Table 27-2 on page 27-10.
Switch(config)# mls qos map cos-dscp 0 8 16 26 32 46
48 56
The switch automatically sets the ingress classification on the
interface to trust the CoS value received in the packet.
Switch(config-if)# mls qos trust cos
If you entered the auto qos voip cisco-phone command, the
switch automatically enables the trusted boundary feature,
which uses the CDP to detect the presence or absence of a
Cisco IP Phone.
Switch(config-if)# mls qos trust device cisco-phone
The switch automatically assigns egress queue usage (as
shown in Table 27-3 on page 27-10) on this interface.
The switch enables the egress expedite queue and assigns
WRR weights to queues 1 and 3. (The lowest value for a WRR
queue is 1. When the WRR weight of a queue is set to 0, this
queue becomes an expedite queue.)
The switch configures the CoS-to-egress-queue map:
• CoS values 0, 1, 2, and 4 select queue 1.
• CoS values 3, 6, and 7 select queue 3.
• CoS value 5 selects queue 4 (expedite queue).
Because the expedite queue (queue 4) contains the VoIP data
traffic, the queue is serviced until empty.
Switch(config)# wrr-queue bandwidth 20 1 80 0
Switch(config)# wrr-queue cos-map 1 0 1 2 4
Switch(config)# wrr-queue cos-map 3 3 6 7
Switch(config)# wrr-queue cos-map 4 5