Cisco Catalyst 3550 Series User Manual

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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 29 Configuring QoS
Configuring Standard QoS
Configuring the DSCP Trust State on a Port Bordering Another QoS Domain
If you are administering two separate QoS domains between which you want to implement QoS features
for IP traffic, you can configure the switch ports bordering the domains to a DSCP-trusted state as shown
in Figure 29-10. Then the receiving port accepts the DSCP-trusted value and avoids the classification
stage of QoS. If the two domains use different DSCP values, you can configure the
DSCP-to-DSCP-mutation map to translate a set of DSCP values to match the definition in the other
domain.
Figure 29-10 DSCP-Trusted State on a Port Bordering Another QoS Domain
Beginning in privileged EXEC mode, follow these steps to configure the DSCP-trusted state on a port
and modify the DSCP-to-DSCP-mutation map. To ensure a consistent mapping strategy across both QoS
domains, you must perform this procedure on the ports in both domains:
46982
Catalyst
3550-12T switch
Catalyst
3550-12T switch
QoS Domain 1 QoS Domain 2
Set interface to the DSCP-trusted state.
Configure the DSCP-to-DSCP-mutation map.
IP traffic
Gigabit
Ethernet
0/3
Gigabit
Ethernet
0/3
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
mls qos Enable QoS on the switch.
Step 3
mls qos map dscp-mutation
dscp-mutation-name in-dscp to out-dscp
Modify the DSCP-to-DSCP-mutation map.
The default DSCP-to-DSCP-mutation map is a null map, which maps
an incoming DSCP value to the same DSCP value.
• For dscp-mutation-name, enter the mutation map name. You can
create more than one map by specifying a new name.
• For in-dscp, enter up to eight DSCP values separated by spaces.
Then enter the to keyword.
• For out-dscp, enter a single DSCP value.
The DSCP range is 0 to 63.
Step 4
interface interface-id Enter interface configuration mode, and specify the interface to be
trusted.
Valid interfaces include physical interfaces.
Step 5
mls qos trust dscp Configure the ingress port as a DSCP-trusted port.

Cisco Catalyst 3550 Series Specifications

General

Brand	Cisco
Model	Catalyst 3550 Series
Category	Network Router
Language	English