Cisco ME 3400 Series, Software Configuration Manual

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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Chapter 33 Configuring QoS
Understanding QoS
Figure 33-4 QoS Groups
You can use QoS groups to aggregate multiple input streams across input classes and policy maps for the
same QoS treatment on the egress port. Assign the same QoS group number in the input policy map to
all streams that require the same egress treatment, and match to the QoS group number in the output
policy map to specify the required queuing and scheduling actions.
You can also use QoS groups to identify traffic entering a particular interface if the traffic must be treated
differently at the output based on the input interface.
You can use QoS groups to configure per-port, per-VLAN QoS output policies on the egress interface
for bridged traffic on the VLAN. Assign a QoS group number to a VLAN on the ingress interface by
configuring a per-port, per-VLAN input policy. Then use the same QoS-group number for classification
at the egress. Because the VLAN of bridged traffic does not change during forwarding through the
switch, the QoS-group number assigned to the ingress VLAN can be used on the egress interface to
identify the same VLAN.
You can use the cpu traffic qos [ cos value | dscp value | precedence value | qos-group value ] global
configuration command to configure a QoS group number for CPU-generated traffic.
Independently you can assign QoS-group numbers at the ingress to any combination of interfaces,
VLANs, traffic flows, and aggregated traffic. To assign QoS-group numbers, configure a QoS group
marking in an input policy map, along with any other marking or policing actions required in the input
policy map for the same service class. This allows the input marking and policing functions to be
decoupled from the egress classification function if necessary because only the QoS group must be used
for egress classification.
To communicate an ACL classification to an output policy, you assign a QoS number to specify packets
at ingress. This example identifies specific packets as part of QoS group 1 for later processing in an
output policy:
Switch(config)# policy-map in-gold-policy
Switch(config-pmap)# class in-class1
Switch(config-pmap-c)# set qos-group 1
Switch(config-cmap-c)# exit
Switch(config-cmap)# exit
You use the set qos-group command only in an input policy. The assigned QoS group identification is
subsequently used in an output policy with no mark or change to the packet. You use the match
qos-group in the output policy.
Note You cannot configure match qos-group for an input policy map.
This example creates an output policy to match the QoS group created in the input policy map
in-gold-policy . Traffic internally tagged as qos-group 1 is identified and processed by the output policy.
Switch(config)# class-map out-class1
Switch(config-cmap)# match qos-group 1
Switch(config-cmap)# exit
The switch supports a maximum of 100 QoS groups.
1. Classify traffic
2. Set qos-group
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152
Switching
functions
1. Match qos-group
2. Output policy