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Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 34 Configuring QoS
Configuring Standard QoS
Mapping DSCP or CoS Values to an Ingress Queue and Setting WTD Thresholds
You can prioritize traffic by placing packets with particular DSCPs or CoSs into certain queues and
adjusting the queue thresholds so that packets with lower priorities are dropped.
Beginning in privileged EXEC mode, follow these steps to map DSCP or CoS values to an ingress queue
and to set WTD thresholds. This procedure is optional.
To return to the default CoS input queue threshold map or the default DSCP input queue threshold map,
use the no mls qos srr-queue input cos-map or the no mls qos srr-queue input dscp-map global
configuration command. To return to the default WTD threshold percentages, use the no mls qos
srr-queue input threshold queue-id global configuration command.
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 mls qos srr-queue input dscp-map
queue queue-id threshold threshold-id
dscp1...dscp8
or
mls qos srr-queue input cos-map
queue queue-id threshold threshold-id
cos1...cos8
Map DSCP or CoS values to an ingress queue and to a threshold ID.
By default, DSCP values 0–39 and 48–63 are mapped to queue 1 and
threshold 1. DSCP values 40–47 are mapped to queue 2 and threshold 1.
By default, CoS values 0–4, 6, and 7 are mapped to queue 1 and threshold
1. CoS value 5 is mapped to queue 2 and threshold 1.
• For queue-id, the range is 1 to 2.
• For threshold-id, the range is 1 to 3. The drop-threshold percentage
for threshold 3 is predefined. It is set to the queue-full state.
• For dscp1...dscp8, enter up to eight values, and separate each value
with a space. The range is 0 to 63.
• For cos1...cos8, enter up to eight values, and separate each value with
a space. The range is 0 to 7.
Step 3 mls qos srr-queue input threshold
queue-id threshold-percentage1
threshold-percentage2
Assign the two WTD threshold percentages for (threshold 1 and 2) to an
ingress queue. The default, both thresholds are set to 100 percent.
• For queue-id, the range is 1 to 2.
• For threshold-percentage1 threshold-percentage2, the range is 1 to
100. Separate each value with a space.
Each threshold value is a percentage of the total number of queue
descriptors allocated for the queue.
Step 4 end Return to privileged EXEC mode.
Step 5 show mls qos maps Verify your entries.
The DSCP input queue threshold map appears as a matrix. The d1 column
specifies the most-significant digit of the DSCP number; the d2 row
specifies the least-significant digit in the DSCP number. The intersection
of the d1 and the d2 values provides the queue ID and threshold ID; for
example, queue 2 and threshold 1 (02-01).
The CoS input queue threshold map shows the CoS value in the top row
and the corresponding queue ID and threshold ID in the second row; for
example, queue 2 and threshold 2 (2-2).
Step 6 copy running-config startup-config (Optional) Save your entries in the configuration file.