Wireless QoS Best Practices

QoS the necessary evil of CCIE Wireless.

1. Best practices are to trust CoS on trunk ports and DSCP on access ports.

2.  Make sure QoS is turned on the switch by the command:

     Switch#show mls qos

     Switch#conf t

     Switch(config)# mls qos

     Switch(config)#interface g0/1
   
     Switch(config-if)# mls qos trust cos

     Switch(config)#interface g0/2
   
     Switch(config-if)# mls qos trust dscp

3.  Cisco Controllers do not know how to map the DSCP to CoS to match what the switch has so you have to map the correct DSCP to CoS value and Cos to DSCP values. The first command provides the the CoS to DSCP map, and the next two are for the DSCP to CoS maps. 

     Switch(config)#mls qos map cos-dscp 0 8 16 26 32 46 48 56

     Switch(config)#mls qos map dscp-cos 26 to 3

     Switch(config)#mls qos map dscp-cos 46 to 5

4.   You may be asked to different types of traffic policy maps, or to match certain kinds of traffic.  The first step is to create a class-map to match your traffic, then create a policy-map and then apply that policy-map to an interface.