In the first part of the MQC review – we examined class maps. These devices place our traffic into containers that we can assign QoS actions to. In this article, we are going to look at policy maps for assigning those actions.

Here I will create a quick class map, verify the class map, and then enter policy map configuration mode:

R1(config)#class-map match-any CM_ICMP

R1(config-cmap)#match access-group 100

R1(config-cmap)#exit

R1(config)#exit

R1#! The access-list 100 is not shown in this configuration

R1#show class-map

 Class Map match-any class-default (id 0)

   Match any 

 Class Map match-any CM_ICMP (id 1)

   Match access-group  100 

R1#conf t

R1(config)#policy-map PM_ICMP

R1(config-pmap)#?

Policy-map configuration commands:

  class        policy criteria

  description  Policy-Map description

  exit         Exit from policy-map configuration mode

  no           Negate or set default values of a command

  rename       Rename this policy-map

R1(config-pmap)#

As you can see from the above configuration, there is not much going on in policy map configuration mode. We can add a description or rename the policy map but that is about it. The magic happens when we enter policy map class configuration for one of the classes that we configured:

R1(config-pmap)#class CM_ICMP

R1(config-pmap-c)#?

Policy-map class configuration commands:

  bandwidth        Bandwidth

  compression      Activate Compression

  drop             Drop all packets

  exit             Exit from class action configuration mode

  log              Log IPv4 and ARP packets

  netflow-sampler  NetFlow action

  no               Negate or set default values of a command

  police           Police

  priority         Strict Scheduling Priority for this Class

  queue-limit      Queue Max Threshold for Tail Drop

  random-detect    Enable Random Early Detection as drop policy

  service-policy   Configure Flow Next

  set              Set QoS values

  shape            Traffic Shaping

  <cr>

Notice these are the QoS actions we are so excited about – things like bandwidth and priority for CBWFQ, compression, policing and shaping, and random-detect for WRED. Notice also you can next policy maps inside each other for even more control. The service-policy keyword would allow this. Thanks to this third step of the MQC process, this service-policy assigns a policy map into this policy map.

Notice also the drop keyword you could use. What a powerful security mechanism this is, dropping the packets specified in your class map.

I hope you will join me in the third part of this series where we examine the third step- the service policy and verification of MQC.