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Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
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Chapter 3 QoS in an AVVID-Enabled Campus Network
Selecting an Access-Layer Switch
Step 1
Configure the switch to trust CoS from the IP phone.
2950G-Access(config)#interface g 0/11
2950G-Access(config-if)#mls qos trust cos
Step 2
Enable the voice and data VLANs.
2950G-Access(config-if)#switchport voice vlan 111
2950G-Access(config-if)#switchport access vlan 11
Step 3
Set the IP phone's trust boundary.
2950G-Access(config-if)#switchport priority extend cos 0
Configuring the Uplink to the Distribution Switch
The ports attached to the distribution layer require a different configuration. These ports must be
configured to trust DSCP or CoS depending on the capabilities of the distribution-layer switch attached.
In the following configuration, port 0/11 illustrates an example where CoS-only classification is used.
Port 0/12 is attached to a Layer 3-aware distribution device and can trust the DSCP arriving from it.
Step 1
Configure DSCP trust.
2950G-Access(config)#interface g 0/11
2950G-Access(config-if)#mls qos trust cos
Step 2
Configure CoS trust.
2950G-Access(config)#interface g 0/12
2950G-Access(config-if)#mls qos trust dscp
Verifying the Configuration
On the Catalyst 2950 access-layer switch, you can verify the configuration by examining the output of
the following commands:
Example 3-16 Displaying QoS CoS Mapping Information
2950-Access#show mls qos maps
Dscp-cos map:
dscp: 0 8 10 16 18
24 26 32 34 40 46 48 56
-----------------------------------------------
cos: 0 1 1 2 2 3 3 4 4 5 5 6 7
Cos-dscp map:
cos: 0 1 2 3 4 5 6 7
--------------------------------
dscp: 0 8 16
26 34 46 48 56
Command
Description
See
show mls qos maps
Displays the QoS CoS mapping information.
show wrr-queue band
Displays the queuing mechanism and the QoS
queue assignments.