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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 37 Configuring Quality of Service
Configuring QoS on Supervisor Engine 6-E, Supervisor Engine 6L-E, Catalyst 4900M, and Catalyst 4948E
QoS Action Restrictions
Action restrictions include the following:
The same actions cannot be performed multiple times in a given direction on different targets. In
other words, it is not possible to police the packets both on port and VLAN in the input direction.
However, the user can police on the input port and on the output VLAN.
Queuing actions are only allowed in the egress direction and only on the physical port.
Percentage-based actions like policer cannot be configured on a VLAN.
Port channel or VLAN configuration can only have a policing or a marking action, not a queueing
action.
QoS Policy Priorities
Policy priorities include the following:
If a policy on a port and a VLAN are configured with conflicting actions (such as policing or
marking actions on both a port and VLAN), the port policy is picked.
If policy on a VLAN on a given port must be overwritten, the user can configure PV policy.
Qos Policy Merging
Applicable policies are applied to a given packet in given direction. For example, configure egress
VLAN-based police and marking, followed by selective queuing on the port, then actions from both
policies will be applied for this packet.
The following policy-map configuration restrictions are imposed on an EtherChannel:
Only policing and marking actions are supported at the EtherChannel level.
Only queuing actions are supported at the physical member port level.
A packet can be marked (DSCP or CoS fields) by the EtherChannel policy. If the physical member port
policy uses a classification based on DSCP or CoS fields, it must be based on the marked (modified)
value. To ensure proper operation, the following restriction is placed on the EtherChannel.
The classification criteria for the policy map on the physical member ports has to based only on one type
of field:
DSCP
Precedence
CoS
Any nonmarking field (no DSCP or CoS based classification)
Table 37-8 Table QoS Policy Associations
Object Action
Physical port Policing, marking, and queuing
VLAN Policing and marking
Port and VLAN (PV) Policing and marking
EtherChannel Policing and marking
EtherChannel member port Queuing