Nested Policy-map

Policy-maps do indeed have the ability to be nested inside other policy maps. When we engage in this nesting behavior, we refer to the policy as a hierarchical policy. This is typically done to configure multiple treatments to QoS. For example – we might want to traffic-shape all traffic to 3 MB; and then inside that 3 MB shaped traffic, guarantee Web traffic at least 1 MB of bandwidth.

Remember, we use a service-policy (normally done with interfaces) to  assign the QoS policies that we define inside the policy-map.

With the nesting of policy maps, there are some restrictions that you should be aware of. For example:

• The set command is not supported on the child policy
• The priority command can be used in either the parent or the child policy, but not both
• The fair-queue command cannot be used in the parent

Here is an example of nesting policy maps:

class-map CM_ALL_TRAFFIC
 match any
!
class-map CM_WEB
  match protocol http
!
policy-map PM_CHILD
 class CM_WEB
  bandwidth 1000
!
policy-map PM_PARENT
 class CM_ALL_TRAFFIC
  shape 3000000
  service-policy PM_CHILD

Verifying your policy-map, is very simple thanks to the following show commands:

show policy-map
show policy-map interface int_name

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Author: Mo Moghaddas

Building zeeg.me to give users more time back and make scheduling a pleasant experience. View all posts by Mo Moghaddas