QoS Configurations on Catalyst Switches 743

Example 10-44 Set the DSCP Value for the Classes (Continued)

CatIOS (config-pmap-c)#set ip dscp 46

CatIOS (config-pmap)#class GOLD-DATA

CatIOS (config-pmap-c)#set ip dscp 18

In this example, all traffic matching the GOLD-DATA access list is marked with a DSCP value of 18, all traffic matching the VOICE-CONTROL access list is marked with a DSCP value of 26, and all traffic matching the VOICE access list is marked with a DSCP value of 46.

Finally, the service-policy command is used to assign the policy map to the input traffic on a specific interface. In Example 10-45, the policy map configuration is applied to interface Gigabit Ethernet 0/2.

Example 10-45 Applying the Policy to the Interface

CatIOS (config)#int gigabitethernet 0/2

CatIOS (config-if)#service-policy input CAT-IOS-IN

Connecting a Catalyst IOS Switch to Distribution Switches or WAN Segments

In Figure 10-12, a WAN router is connected to port 5. Typically you will trust the Layer 3 markings from a WAN device. Assuming that the switch is a 6500 or a 3500, to configure the switch to trust the DSCP values received on port 5, you must place the mls qos trust dscp command on interface 5. If the switch is a 4500, the qos trust dscp command is configured on interface 5.

Displaying QoS Settings for the Catalyst IOS Switch

Several show commands enable you to verify the QoS configuration of the Catalyst OS switch. The show mls qos interface queueing command enables you to display the QoS queuing strategy for the Catalyst 3550 switch. In Example 10-46, egress expedited queuing (priority queuing) has been enabled on interface gigabit 0/1, causing Queue 4 to become the priority queue. All frames with a CoS value of 5, 6, or 7 are placed in this queue.

Example 10-46 The show mls qos interface queueing Command

3550 #show mls qos interface queueing

GigabitEthernet0/1

Ingress expedite queue: dis Egress expedite queue: ena wrr bandwidth weights: qid-weights

1 - 25

2 - 25

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QoS Configurations on Catalyst Switches 745

In Example 10-48, the QoS configuration of Fast Ethernet 0/10 on the Catalyst 3550 switch displays. In the earlier example, interface Fast Ethernet 0/10 was configured to trust the CoS values received.

Example 10-48 The show mls qos interface Command F0/10

3550 t#show mls qos int g0/10

GigabitEthernet0/10

trust state: trust cos

COS override: dis default COS: 0

DSCP Mutation Map: Default DSCP Mutation Map

The show qos interface command enables you to display the current QoS configuration information about the specified interface in a Catalyst 4500. In Example 10-49, QoS has been enabled globally in the switch as well as on this port; however, the trust state for port 4/5 is configured for untrusted. Although QoS has been enabled, this port transmits packets without regard to the CoS or DSCP values on the packets.

Example 10-49 The show qos interface Command: Untrusted

In Example 10-50, port 3/1 on a Catalyst 4500 has been configured to trust the DSCP values of packets. Any packet that matches the DSCP classification for admittance into the priority queue is transmitted immediately.

Example 10-50 The show qos interface Command: Trust DSCP

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