Configuring The Dscp-To-Cos Map - Cisco WS-C3550-12G Software Configuration Manual

Configuring QoS

Configuring the DSCP-to-CoS Map

You use the DSCP-to-CoS map to generate a CoS value, which is used to select one of the four egress
queues.
Table 20-5
Table 20-5 Default DSCP-to-CoS Map
DSCP value
CoS value
If these values are not appropriate for your network, you need to modify them.
Beginning in privileged EXEC mode, follow these steps to modify the DSCP-to-CoS map:
Command
Step 1
configure terminal
Step 2
mls qos map dscp-cos dscp-list to cos
Step 3 end
Step 4
show mls qos maps dscp-to-cos
Step 5
copy running-config startup-config
To return to the default map, use the no mls qos dscp-cos global configuration command.
This example shows how to map DSCP values 0, 8, 16, 24, 32, 40, 48, and 50 to CoS value 0 and to
display the map:
Switch# configure terminal
Switch(config)# mls qos map dscp-cos 0 8 16 24 32 40 48 50 to 0
Switch(config)# end
Switch# show mls qos maps dscp-cos
Dscp-cos map:
Note In the above DSCP-to-CoS map, the CoS values are shown in the body of the matrix. The d1 column
specifies the most-significant digit of the DSCP; the d2 row specifies the least-significant digit of the
DSCP. The intersection of the d1 and d2 values provides the CoS value. For example, in the
DSCP-to-CoS map, a DSCP value of 08 corresponds to a CoS value of 0.
Catalyst 3550 Multilayer Switch Software Configuration Guide
20-42
shows the default DSCP-to-CoS map.
0–7 8–15
0 1
Purpose
Enter global configuration mode.
Modify the DSCP-to-CoS map.
•
•
The DSCP range is 0 to 63; the CoS range is 0 to 7.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
d1 : d2 0 1 2 3 4
---------------------------------------
0 : 00 00 00 00 00 00 00 00 00 01
1 : 01 01 01 01 01 01 00 02 02 02
2 : 02 02 02 02 00 03 03 03 03 03
3 : 03 03 00 04 04 04 04 04 04 04
4 : 00 05 05 05 05 05 05 05 00 06
5 : 00 06 06 06 06 06 07 07 07 07
6 : 07 07 07 07
16–23 24–31 32–39
2 3 4
For dscp-list, enter up to 8 DSCP values separated by spaces. Then
enter the to keyword.
For cos, enter the CoS value to which the DSCP values correspond.
5 6 7 8 9
Chapter 20
40–47 48–55 56–63
5 6 7
Configuring QoS
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