Workaround to Configure CBWFQ on Sub-Interfaces

If you ever tried to configure CBFQW (Class Based Weighted Fair Queuing) in a sub interface, you may have seen the router is rejecting the command saying "Not supported on subinterfaces"

In order to make this work, we have to call the policy map in a another policy map and apply the parent policy map in the interface.

Let's see how it is done..

Following is a typical policy map for CBWFQ;

R1(config)#class-map ICMP
R1(config-cmap)#match protocol icmp 

R1(config)#policy-map CBWFQ
R1(config-pmap)#class ICMP
R1(config-pmap-c)#bandwidth percent 10

Now let's create the parent policy map

R1(config)#policy-map PARENT-FOR-CBWFQ
R1(config-pmap)#class class-default
R1(config-pmap-c)#shape average percent 100
R1(config-pmap-c)#service-policy CBWFQ

Above policy map is created to match all the traffic going through and shaping it to 100% meaning no shaping, then call the policy map CBWFQ..

Shaping is needed here unless otherwise IOS MQC/HQF does not let nested policy maps to apply to an interface..

Now we can apply it to an interface finally..

R1(config-subif)#service-policy output PARENT-FOR-CBWFQ