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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 26 Configuring QoS
Configuring QoS
Configuration Guidelines
Note These guidelines are applicable only if your switch is running the EI.
Before beginning the QoS configuration, you should be aware of this information:
• If you have EtherChannel ports configured on your switch, you must configure QoS classification,
policing, mapping, and queueing on the individual physical ports that comprise the EtherChannel.
You must decide whether the QoS configuration should match on all ports in the EtherChannel.
• It is not possible to match IP fragments against configured IP extended ACLs to enforce QoS. IP
fragments are sent as best-effort traffic. IP fragments are denoted by fields in the IP header.
• All ingress QoS processing actions apply to control traffic (such as spanning-tree bridge protocol
data units [BPDUs] and routing update packets) that the switch receives.
• Only an ACL that is created for physical interfaces can be attached to a class map.
• Only one ACL per class map and only one match command per class map are supported. The ACL
can have multiple access control entries, which are commands that match fields against the contents
of the packet.
• Policy maps with ACL classification in the egress direction are not supported and cannot be attached
to an interface by using the service-policy input policy-map-name interface configuration
command.
• In a policy map, the class named class-default is not supported. The switch does not filter traffic
based on the policy map defined by the class class-default policy-map configuration command.
• For more information about guidelines for configuring ACLs, see the “Classification Based on QoS
ACLs” section on page 26-5.
• For information about applying ACLs to physical interfaces, see the “Guidelines for Applying ACLs
to Physical Interfaces” section on page 25-6.
Note Do not configure QoS when IEEE 802.3X flowcontrol is configured on the switch. Before configuring
QoS on an interface, make sure to disable flowcontrol on the switch.
Configuring Classification Using Port Trust States
This section describes how to classify incoming traffic by using port trust states:
• Configuring the Trust State on Ports within the QoS Domain, page 26-11
• Configuring the CoS Value for an Interface, page 26-13
• Configuring Trusted Boundary, page 26-13
• Enabling Pass-Through Mode, page 26-15