Cisco ME 3400 Series, Software Configuration Manual

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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 33 Configuring QoS
Understanding QoS
Classification Based on VLAN IDs
With classification based on VLAN IDs, you can apply QoS policies to frames carried on a
user-specified VLAN for a given interface. You can use hierarchical policy maps for per-VLAN
classification on trunk ports if the switch is running the metro IP access or metro access image.
Per-VLAN classification is not required on access ports because access ports carry traffic for a single
VLAN. If you try to attach an input per-port, per VLAN hierarchical policy to a port that is not a trunk
port, the configuration is rejected.
The switch supports two policy levels: a parent level and a child level. With the QoS parent-child
structure, you can reference a child policy in a parent policy to provide additional control of a specific
traffic type. For per-port, per-VLAN QoS, the parent-level class map specifies only the VLAN match
criteria, and the child-level class maps provide more detailed classification for frames matching the
parent-level class map.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.
Note
A per-port, per-VLAN parent-level class map supports only a child-policy association; it does not allow
any actions to be configured. In addition, for a parent-level class map, you cannot configure an action or
a child-policy association for the class
class-default .
Per-port, per-VLAN QoS has these limitations:
• You can apply a per-port, per-VLAN hierarchical policy map only to trunk ports.
•
You can configure classification based on VLAN ID only in the parent level of a per-port, per-VLAN
hierarchical policy map.
• 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 ACL ), you must be careful to ensure that these
VLANs are not carried on any port other than the one on which this per-port, per-VLAN policy is
attached. Not following this restriction 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.
In this example, the class maps in the child-level policy map specify matching criteria for voice, data,
and video traffic, and the child policy map sets the action for input policing each type of traffic. The
parent-level policy map specifies the VLANs to which the child policy maps are applied on the specified
port.
Switch(config)# class-map match-any dscp-1 data
Switch(config-cmap)# match ip dscp 1
Switch(config-cmap)# exit
Switch(config)# class-map match-any dscp-23 video
Switch(config-cmap)# match ip dscp 23
Switch(config-cmap)# exit
Switch(config)# class-map match-any dscp-63 voice
Switch(config-cmap)# match ip dscp-63
Switch(config-cmap)# exit
Switch(config)# class-map match-any customer-1-vlan
Switch(config-cmap)# match vlan 100
Switch(config-cmap)# match vlan 200
Switch(config-cmap)# match vlan 300
Switch(config-cmap)# exit