13-13
Catalyst 2950 Desktop Switch Software Configuration Guide
78-11380-03
Chapter 13 Configuring QoS
Configuring QoS
Configuring the CoS Value for an Interface
Note Both the enhanced and standard software images support this feature.
QoS assigns the CoS value specified with the mls qos cos interface configuration command to untagged
frames received on trusted and untrusted ports.
Beginning in privileged EXEC mode, follow these steps to define the default CoS value of a port or to
assign the default CoS to all incoming packets on the port:
To return to the default setting, use the no mls qos cos {default-cos | override} interface configuration
command.
Configuring a QoS Policy
Note This feature is available only if your switch is running the enhanced software image.
Configuring a QoS policy typically requires classifying traffic into classes, configuring policies applied
to those traffic classes, and attaching policies to interfaces.
For background information, see the “Classification” section on page 13-4 and the “Policing and
Marking” sectiononpage13-6.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify the interface to be trusted.
Valid interfaces include physical interfaces.
Step 3
mls qos cos {default-cos | override} Configure the default CoS value for the port.
For default-cos, specify a default CoS value to be assigned to a port. If the
port is CoS trusted and packets are untagged, the default CoS value becomes
theCoSvalueforthepacket.TheCoSrangeis0to7.Thedefaultis0.
Use the override keyword to override the previously configured trust state
of the incoming packets and to apply the default port CoS value to all
incoming packets. By default, CoS override is disabled.
Use the override keyword when all incoming packets on certain ports
deserve higher priority than packets entering from other ports. Even if a port
was previously set to trust DSCP, this command overrides the previously
configured trust state, and all the incoming CoS values are assigned the
default CoS value configured with this command. If an incoming packet is
tagged, the CoS value of the packet is modified with the default CoS of the
port at the egress port.
Step 4
end Return to privileged EXEC mode.
Step 5
show mls qos interface Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
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