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Chapter 3 QoS in an AVVID-Enabled Campus Network
Selecting a Distribution-Layer Switch
Catalyst 3550 as a Distribution-Layer Switch
shows a general model for the Catalyst 3550 as a distribution device (as illustrated in the
QoS configurations discussed in this chapter).
Figure 3-16 General Model for Catalyst 3550 as a Distribution Switch in QoS Configurations
For the Catalyst 3550, QoS requires the following changes to the configuration of the distribution
switch:
1.
Enable QoS.
2.
Change the default CoS-to-DSCP mapping table so that CoS and DSCP PHB label behavior can be
maintained throughout the network.
3.
Enable priority queuing (per port). Default admission to priority queue matches our requirements.
4.
Configure ACLs, associate them with service policies, and apply the policy to an interface.
5.
Configure CoS or DSCP trust for access Layer 2 and Layer 3 aware switches.
Enabling QoS
To enable QoS on the Catalyst 3550, do the following:
Step 1
Enable QoS.
3550G-Dist(config)#mls qos
Si
Si
IP
VVID=112
6500 w/ PFC
4000
3500
VLAN=12
IP
VVID=111
VLAN=11
IP
VVID=110
VLAN=10
Distribution
Access
3550
3550
7200 WAN
router
74707
0/1
0/2
0/2
0/3
0/1
0/3
0/1