Cisco ME 3400G-2CS - Ethernet Access Switch Software Configuration Manual page 600

Chapter 30 Configuring QoS
Configuration Examples for Policy Maps
These steps activate all applicable Fast Ethernet and Gigabit Ethernet ports:
Switch(config)# interface range gigabitethernet0/1-2, fastethernet0/1-12
Switch(config-if-range)# no shutdown
Switch(config-if-range)# exit
You should use the same procedure when adding a class to an attached output service policy.
Problems can occur if you do not follow the previous sequence.
Note
When a policy map is attached to an interface, all traffic that does not explicitly match the configured
class maps within the policy map should go through the default queue (class class-default). However,
in some cases, traffic that does not explicitly match the output policy-map classes could go through more
than one queue. This queuing problem can occur when you do not follow the previous procedure and do
not attach an output policy to all active ports.
For example, consider this case where only two ports are configured with an output policy and we want
to delete a class in the output policy.
Shut down two ports:
Switch(config)# interface range fastethernet0/1-2
Switch(config-if-range)# shutdown
Switch(config-if-range)# exit
Detach the output policy from both ports:
Switch(config)# interface range fastEthernet0/1-2
Switch(config-if)# no service-policy output output1-2
Switch(config-if)# exit
Delete a class in the output policy:
Switch(config)# policy-map output1-2
Switch(config-pmap)# no class bronze-out
Switch(config-pmap-c)# exit
Attach the output policy to only one port and not to the other:
Switch(config)# interface FastEthernet0/1
Switch(config-if)# service-policy output output1-2
Switch(config-if)# exit
Enable both ports:
Switch(config)# interface range fastethernet0/1-2
Switch(config-if-range)# no shutdown
Switch(config-if-range)# exit
At this point, when traffic leaves Fast Ethernet port 2, instead of going through a single default-queue,
it goes through the same number of queues as there are classes defined in the output policy-map attached
to Fast Ethernet port 1. In this case, it would be three. In some cases, packets for a flow out of Fast
Ethernet port 2 might be reordered if a flow splits across more than one queue. You can avoid this
problem by leaving ports in a shut-down state until an output policy is attached.
Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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