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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 26 Configuring QoS Configuring QoS

Configuring QoS

Before configur ing QoS, you must have a thorough unde rstand ing of thes e items:
The type s of applica tions used and the traffic patterns on yo ur network.
Traffic characteristics and needs of your network. Is the traffic bursty? Do you need to reserve
bandwidt h for voice and video stre ams?
Bandwidt h requir ement s and speed of th e network.
Locat ion of cong estion po ints in the ne twork.
This se ction de scribe s how to configure QoS on your swit ch:
Note If your switch i s running th e SI, you can co nfigure only the feature s describ ed in the Configuring
Classification Using Port Trust States and the Configur ing CoS and WRR s e ctio ns. You can also
display the Q oS informa tion as descr ibed in the Displaying QoS Information section.
Default QoS Configu ration, pa ge 26-9
Configuration Gu idelines, page 26-10
Configuring Classification Using Port Trust States, page 26-10
Configuring a QoS Policy, page 26-16
Configuring Co S Ma ps, page 2 6-24
Configuring Co S and WRR , pa ge 26 -27

Default QoS Configuration

This is the default QoS configuration:
Note You can configure policy maps, policers, the CoS-to-DSCP map, and the DSCP-to-CoS map only if your
switch is running th e EI.
The default port CoS value is 0.
The CoS value of 0 is assigned to all incoming packets.
The default port trust state is untrusted.
No policy maps ar e configured.
No policers are configured.
The default CoS-to-DSCP map is shown in Table 26-3.
The de fault D SCP- to-C oS m ap is shown in Table 26-4.
For default QoS and WRR values, see the Configuring CoS and WRR se ctio n o n pa ge 26-27 .
Note In software releases earlier than Release 12.1(11)EA1, the switch uses the CoS value of incoming
packets without modifying the DSCP value. You can configure this by enabling pass-through mode on
the port. For more information, see the Enabling Pass-T hro ugh Mode section on page 26-15.