JUNOSe 9.0.x Policy Management Configuration Guide > Merging Policies > Merging Policies Overview

Merging Policies Overview

Merging policies enables you to create multiple policy attachments at an attachment point, resulting in a merged policy that is created and attached at this interface. Executing more than one policy attachment command with the same attachment type at an interface triggers a policy merge through the CLI.

In Profile Configuration mode, policy interface commands for IP and L2TP allow attachments to be merged into any existing merge-capable attachment at an attachment point. Service Manager can request that multiple interface profiles be applied or removed at an interface as part of service activation or deactivation. Service Manager also specifies whether or not the attachments created from these interface profiles are persistent on subsequent reloads.

An interface and an attachment type identify an attachment point. The policies referenced by the component attachments merge into a new policy, which then attaches at the attachment point. The set of component policies are ordered alphabetically by name. This order determines how any merge conflicts are resolved, with the most recently executed command taking precedence.

With policy merging, a set of policies is combined to form a single new policy, which is a union of all the component policies. Classifier groups and policy rules from each component combine to create the merged policy as in the following example:

host1(config)#interface atm 5/0.1

host1(config-subif)#ip policy input p1 statistics enable merge

host1(config-subif)#ip policy input p2 statistics enable merge

host1(config-subif)#ip policy input p3 statistics enable merge

host1(config-subif)#ip policy output p4 statistics enable merge

host1(config-subif)#ip policy output p5 statistics enable merge

host1(config-subif)#exit

The example internally results in the following, where policies p1 + p2 + p3 = mpl_10 and policies p4 + p5 = mpl_11.

interface atm 5/0.1

ip policy input mpl_10 statistics enable merge

ip policy output mpl_11 statistics enable merge

exit

The classifier list referenced by the classifier group is neither split or merged. If a merged policy already exists for a set of component policies, then the merged policy is used for the attachment. An attachment enables a merged policy to have one or more attachments.