Cisco Cisco IOS Software Release 12.2(27)SBC

QoS—VLAN Tag-Based

Information About QoS—VLAN Tag-Based

QoS - VLAN Tag-Based

VLAN-Group Policies and Inheritance

For non-VLAN-group QoS policies, the PRE3 supports the configuration of shaping only at the
subinterface level and a hierarchical queuing policy at the virtual template level. In this case, the PPP
session traffic uniquely inherits the policy on the virtual template and the aggregate of all of the PPP
session traffic is also shaped by the subinterface policy.

All subinterfaces that are not part of a VLAN group and that do not have a service policy attached inherit
the policy applied on the class-default class of a VLAN-group policy.

For sessions terminated on a subinterface that is part of a VLAN-group policy, the following occurs:

•

If the virtual template applied to the subinterface does not have a QoS policy (non-VLAN-group),
the virtual access interface (VAI) that is created when PPP session creation occurs does not uniquely
inherit the policy inherited by the subinterface. For example, suppose a subinterface policy shapes
traffic to 2 Mbps and two PPPoE sessions initiate. The total traffic from both of the PPPoE sessions
is aggregately shaped to 2 Mbps. Each PPP session traffic is not shaped uniquely to 2 Mbps.

•

If the virtual template applied to the subinterface has a QoS policy (for example, a non-queuing
policy that specifies policing and marking for the PRE2 or all QoS actions for the PRE3), each PPP
session traffic is uniquely influenced by the policy defined at the virtual template. For example,
suppose a hierarchical QoS policy is configured to police traffic to 2 Mbps. Each PPPoE session
traffic is uniquely policed to 2 Mbps. The policy on the subinterface has no affect.

Aggregate Session Traffic

You cannot shape the aggregate session traffic by applying a shaping policy to a VLAN group. Instead,
when applying queuing policies to sessions, shape the aggregate session traffic by applying a shaping
policy to an 802.1Q VLAN or QinQ subinterface. For more information, see the QoS: Hierarchical
Queuing for Ethernet DSLAMs feature module for Cisco IOS Release 12.2(31)SB2.

Although you cannot shape PPP sessions, you can police the sessions.

System Limits for QoS—VLAN Tag-Based

Table 1

lists the system limits for the QoS—VLAN Tag-Based feature.

Table 1

System Limits for QoS—VLAN Tag-Based

Class Maps
per Policy Map

Excludes the class-default class map.

VLAN Groups
per VLAN-Group Policy

Total Number Class Maps
per VLAN-Group Policy

Includes the class maps configured for child policies applied to each match-VLAN class and includes the class-default class
of the VLAN-group policy.

255