# External Parent Groups

Parent groups act as nonleaf nodes in a hierarchical policy. You can build a hierarchy of policers using classifier groups as leaf nodes and parent groups as parent nodes within a policy list. Each classifier group (with or without a rate limit) can point to a single parent group and that parent group can point to another parent group. To avoid undefined hierarchies, each node can only point to one other node.

The inter-interface hierarchical model includes references to parent groups that are defined externally from a policy list. This enables you to define hierarchical nodes outside the scope of a policy-list attachment. In Global Configuration mode, each external parent group can have a rate-limit profile defined and have a reference to another external parent group.

The classifier groups and parent groups within a policy list can point to external parent groups for all policies that implement hierarchical policies. Each external parent group reference must also have a policy parameter name.

External parent group names are global. Internal parent group names are local to each policy configuration. Because both of these name spaces are different, you can configure overlapping names.