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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 33 Configuring QoS Configuring QoS
Configuring Per-Port Per-VLAN QoS with Hierarchical Input Policy Maps
Per-port, per-VLAN QoS allows classification based on VLAN IDs for applying QoS for frames received
on a given interface and VLAN. This is achieved by using a hierarchical policy map, with a parent policy
and a child policy.
Note these guidelines and limitations when configuring per-port, per-VLAN QoS:
• The feature is supported only by using a two-level hierarchical input policy map, where the parent
level defines the VLAN-based classification, and the child level defines the QoS policy to be applied
to the corresponding VLAN or VLANs.
• You can configure multiple service classes at the parent level to match different combinations of
VLANs, and you can apply independent QoS policies to each parent-service class using any child
policy map
• A policy is considered a parent policy map when it has one or more of its classes associated with a
child policy map. Each class within a parent policy-map is called a parent-class. In parent classes,
you can configure only the match vlan class-map configuration command. You cannot configure
the match vlan command in classes within the child policy map.
• A per-port, per-VLAN parent level class map supports only a child-policy association; it does not
allow any actions to be configured. For a parent-level class map, you cannot configure an action or
a child-policy association for the class class-default.
• You cannot configure a mixture of Layer 2 and Layer 3 class maps in a child polic y map. Wh en you
attempt to associate such a child policy map with a parent policy, the configuration is rejected.
However, you can associate Layer 2 child policies and Layer 3 child policies with different
parent-level class maps.
• Per-port, per-VLAN QoS is supported only on IEEE 802.1Q trunk ports.
• When the child policy-map attached to a VLAN or set of VLANs contains only Layer 3
classification (match ip dscp, match ip precedence, match IP ACLs), take care to ensure that
these VLANs are not carried on any other port besides the one on which the per-port, per-vlan policy
is attached. Not following this rule could result in improper QoS behavior for traffic ingressing the
switch on these VLANs.
• We also recommend that you restrict VLAN membership on the trunk ports to which the per-port,
per-VLAN is applied by using the switchport trunk allowed vlan interface configuration
command. Overlapping VLAN membership between trunk ports that have per-port, per-VLAN
policies with Layer 3 classification could also result in unexpected QoS behavior.
Configuring per-port, per-VLAN QoS includes these tasks:
• Creating Child-Policy Class Maps, page 33-48
• Creating Parent-Policy Class Maps, page 33-49
• Creating Child Policy Maps, page 33-49
• Creating a Parent Policy Map, page 33-50
• Attaching a Parent Policy Map to an Interface, page 33-50