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Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 33 Configuring QoS
Understanding QoS
When configuring policing on an SVI, you can create and configure a hierarchical policy map with these
two levels:
• VLAN level—Create this primary level by configuring class maps and classes that specify the port
trust state or set a new DSCP or IP precedence value in the packet. The VLAN-level policy map
applies only to the VLAN in an SVI and does not support policers.
• Interface level—Create this secondary level by configuring class maps and classes that specify the
individual policers on physical ports the belong to the SVI. The interface-level policy map only
supports individual policers and does not support aggregate policers. Beginning with Cisco IOS
Release 12.2(25)SED, you can configure different interface-level policy maps for each class defined
in the VLAN-level policy map.
See the “Classifying, Policing, and Marking Traffic on SVIs by Using Hierarchical Policy Maps” section
on page 33-53 for an example of a hierarchical policy map.
Figure 33-5 shows the policing and marking process when hierarchical policy maps on an SVI.
Figure 33-5 Policing and Marking Flowchart on SVIs
92355
Ye s
Ye s
No
No
Pass
through Drop
Mark
Get the VLAN and
interface-level classification
results for the packet.
Is an interface-level policer
configured for this packet?
Check if the packet is in the
profile by querying the policer.
Check out-of-profile action
configured for this policer.
Drop packet.
Modify DSCP according to the
policed-DSCP map. Generate
a new QoS label.
Start
Done
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