Qos Configuration For The Distribution Layer - Cisco WS-C3550-12G Software Configuration Manual

Chapter 20 Configuring QoS
Command
Step 17 wrr-queue cos-map 4 6 7
Step 18 end
Step 19
show class-map videoclass
show policy-map videopolicy
show mls qos maps [cos-dscp | dscp-cos]
show mls qos interface queueing
Step 20
copy running-config startup-config

QoS Configuration for the Distribution Layer

This example focuses on the configuration steps for the Catalyst 3550-12G multilayer switch at the
distribution layer (see
edge of the network, fewer classification steps are needed at the distribution layer switch.
For the connection to the common wiring closet, Gigabit Ethernet interface 0/1 on the multilayer switch
is configured to trust the received CoS value. In this situation, the default CoS-to-DSCP map on the
multilayer switch is sufficient. For information on the default map settings, see the
CoS-to-DSCP Map" section on page
For the connection to the intelligent wiring closet, Gigabit Ethernet interface 0/2 on the multilayer
switch is configured to trust the received DSCP value. The DSCP-to-threshold map also needs to be
configured on this ingress interface so that on the egress interface, WRED can provide congestion
avoidance control. By default, all DSCP values are mapped to threshold 1.
You need to configure several of the switch maps from their default settings. The object of the
configuration is to have only DSCP value 56 sent to the expedite queue (queue 4). The default
CoS-to-egress-queue map is sufficient; however, you need to configure the DSCP-to-CoS map so that
DSCP values 57 to 63 map to CoS 5.
For the egress interface, Gigabit Ethernet interface 0/5, WRR weights need to be configured by using
the wrr-queue bandwidth interface configuration command. WRED needs to be enabled and the
threshold percentages configured for each queue. The bandwidth allocated to each queue must be
configured to determine the ratio of the frequency at which packets are dropped from the queue.
Beginning in privileged EXEC mode, follow these steps to configure the multilayer switch at the
distribution layer:
Command
Step 1
configure terminal
Step 2 mls qos
Step 3 interface gigabitethernet0/1
Step 4 mls qos trust cos
78-11194-03
Purpose
Configure the CoS-to-egress-queue map so that CoS values 6
and 7 select queue 4 (this is the default setting).
Because the default DSCP-to-CoS map has DSCP values 56 to 63
mapped to CoS value 7, the matched traffic that is set to DSCP 56
goes to the queue 4, the priority queue.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Figure 20-10). Because the classification was performed by the switches at the
20-39.
Purpose
Enter global configuration mode.
Enable QoS on the switch.
Enter interface configuration mode, and specify the ingress interface that
is connected to the common wiring closet.
Classify incoming packets on this port by using the packet CoS value.
Catalyst 3550 Multilayer Switch Software Configuration Guide
QoS Configuration Examples
"Configuring the
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