Cisco Systems 4500 Enabling DBL on Specific CoS Values

37-25
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 37 Configuring Quality of Service Configuring QoS on Supervisor Engines II-Plus, II+10GE, IV, V, V-10GE, 4924, 4948, and 4948-10GE
Provided the value has been set according to your network policies, you must configure trust DSCP on
the ingress interface of the aggressive flow that DBL will throttle:
Interface ingress
qos trust dscp
Enabling DBL on Specific CoS Values
You might need to use CoS values to selectively apply DBL if you intend to use non-IP packets or
double-tagged packets (for example, Q-in-Q).
For single-tagged IP packets, use the following approach. Specify the global qos dbl dscp-based
command as shown in the “Enabling DBL on Specific IP DSCP Values” section on page 37-24.
Interface ingress
switchport mode trunk
qos trust cos
To enable DBL non-IP or double-tagged packets, perform this task:
Note For more details on using CoS Mutation, refer to the “Configuring CoS Mutation” section on page 37-36.
To selectively enable DBL on CoS values 2 and 3:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# qos dbl
Switch(config)# end
Switch# configure terminal
Switch(config)# class-map cos
Switch(config-cmap)# match cos 2 3
Switch(config-cmap)# exit
Switch(config)# policy-map cos
Switch(config-pmap)# class cos
Command Purpose
Step 1 Switch(config)# qos dbl Enables DBL globally.
Step 2 Switch(config)# end Exits configuration mode.
Step 3 Switch(config)# class-map cos Defines a traffic class.
Step 4 Switch(config-cmap)# match cos x y Specifies CoS values used as match criteria.
Step 5 Switch(config-cmap)# exit Returns to global configuration mode.
Step 6 Switch(config)# policy-map cos Creates a policy map with a user-specified name.
Step 7 Switch(config-pmap)# class cos Specifies the class map to be used by the policy map.
Step 8 Switch(config-pmap-c)# dbl Enables DBL on the policy.
Step 9 Switch(config-pmap-c)# end Returns to EXEC mode.
Step 10 Switch# show policy-map cos Verifies configuration.
Step 11 Switch# configure terminal Enters global configuration mode.
Step 12 Switch(config)# interface gigabitEthernet 1/20 Applies the configuration to an interface.
Step 13 Switch(config-if)# service-policy output cos Attaches the policy map to the interface.
Step 14 Switch# show policy-map interface Verifies the configuration.