Cisco Catalyst 3550 series Software Configuration Manual page 605

Chapter 29 Configuring QoS
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 29-3 Generated Auto-QoS Configuration
Description
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
If 10/100 Ethernet ports are present, the switch automatically
configures the buffer size of the minimum-reserve levels 5, 6,
7, and 8:
Level 5 can hold 170 packets.
•
Level 6 is not used.
•
Level 7 can hold 65 packets.
•
• Level 8 can hold 26 packets.
The switch automatically sets the ingress classification on the
interface to trust the CoS value received in the packet.
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.
The switch automatically assigns egress queue usage (as
shown in Table 29-2 on page
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.)
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.
78-11194-09
For information about the trusted boundary feature, see the
Ensure Port Security" section on page
Table 29-1 on page 29-18.
29-18) on this interface.
"Configuring a Trusted Boundary to
29-32.
Table 29-3
Automatically Generated Command
Switch(config)# mls qos
Switch(config)# mls qos map cos-dscp 0 8 16 26 32 46
48 56
Switch(config)# mls qos min-reserve 5 170
Switch(config)# mls qos min-reserve 6 10
Switch(config)# mls qos min-reserve 7 65
Switch(config)# mls qos min-reserve 8 26
Switch(config-if)# mls qos trust cos
Switch(config-if)# mls qos trust device cisco-phone
Switch(config-if)# wrr-queue bandwidth 20 1 80 1
Switch(config-if)# no wrr-queue cos-map
Switch(config-if)# wrr-queue cos-map 1 0 1 2 4
Switch(config-if)# wrr-queue cos-map 3 3 6 7
Switch(config-if)# wrr-queue cos-map 4 5
Switch(config-if)# priority-queue out
Catalyst 3550 Multilayer Switch Software Configuration Guide
Configuring Auto-QoS
to the interface.
29-19