Cisco IE 4000, Software Configuration Manual

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581
Configuring QoS
Understanding QoS
Figure 79 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.
Classification Based on VLAN IDs
With classification based on VLAN IDs, you can apply QoS policies to frames carried on a user-specified VLAN for a given
interface. Per-VLAN classification is not required on access ports because access ports carry traffic for a single VLAN.
If you try to attach an input per-port, per VLAN hierarchical policy to a port that is not a trunk port, the configuration is
rejected.
1. Classify traffic
2. Set qos-group
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152
Switching
functions
1. Match qos-group
2. Output policy