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Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
956467
Chapter 3 QoS in an AVVID-Enabled Campus Network
Selecting an Access-Layer Switch
For the Catalyst 4000 with Supervisor II, QoS requires the following changes to the configuration of the
access switch:
1.
Enable QoS globally.
2.
Verify the queue admission configuration.
3.
Configure the IP phone port queuing.
4.
Configure the uplink to the distribution switch.
Enabling QoS
By default, only one queue is enabled on the Catalyst 4000 line of switches. To enable the second queue,
use the set qos map command. VoIP Control (CoS of 3) frames should be placed into the second queue.
These maps must be configured in pairs of CoS values because the Catalyst 4000 examines only the first
two CoS bits. To enable QoS and establish the second queue, do the following.
Step 1
Enable QoS.
cat4k> (enable) set qos enable
Step 2
Map the CoS categories to the queues.
cat4k> (enable) set qos map 2q1t 1 1 cos 0-1
cat4k> (enable) set qos map 2q1t 2 1 cos 2-3
cat4k> (enable) set qos map 2q1t 2 1 cos 4-5
cat4k> (enable) set qos map 2q1t 2 1 cos 6-7
Verifying Queue Admission Configuration
To verify the queue admission configuration on the Catalyst 4000, use the following command (shown
with its associated output):
cat4k> (enable)
show qos info runtime
Run time setting of QoS:
QoS is enabled
All ports have 2 transmit queues with 1 drop thresholds (2q1t).
Default CoS = 0
Queue and Threshold Mapping:
Queue Threshold CoS
----- --------- ---------------
1 1 0 1
2 1 2 3 4 5 6 7
Configuring IP Phone Port Queuing
In the Catalyst OS Release 5.5.1, the Catalyst 4000 line does not offer any advanced IP phone queuing
features. Because of this, the Catalyst 4000 depends on the default CoS marking and enforcement on the
IP phone.
Configuring the Uplink Interface to the Distribution Switch
Queuing is automatically enabled when QoS is been enabled and classification and queue admission
have been configured. Therefore, no special queuing or scheduling commands need to be configured on
the Catalyst 4000 side of the link (from the access-layer Catalyst 4000 to the distribution-layer
Catalyst 6500).