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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
Platform Hardware Capabilities
Prerequisites for Applying a QoS Service Policy
Unlike the switch QoS model, there is no prerequisite for enabling QoS on various targets. Only
attachment of a service policy enables QoS, and detachment of that policy disables QoS on that target.
Restrictions for Applying a QoS Service Policy
Traffic marking can be configured on an interface, a VLAN, or a port and VLAN. An interface can be a
Layer 2 access port, a Layer 2 switch trunk, a Layer 3 routed port, or an EtherChannel. A policy is
attached to a VLAN using the vlan configuration mode.
Attaching QoS service policy to VLANs and EtherChannel is described in the “Policy Associations”
section on page 37-85.
Classification
Catalyst 4900M, Catalyst 4948E, Supervisor Engine 6-E, and Supervisor Engine 6L-E support
classification of Layer 2, IP, IPv6 packets, and ARP packets. Packet marking performed on input can be
matched in the output direction. The previous table lists the full set of capabilities. By default, Catalyst
4900M, Catalyst 4948E, Supervisor Engine 6-E, and Supervisor Engine 6L-E also support classification
resources sharing.
By default, when the same policy is attached to a port or a VLAN or on per-port per-VLAN targets, ACL
entries are shared on Catalyst 4900M, Catalyst 4948E, Supervisor Engine 6-E, and Supervisor Engine
6L-E. Even though CAM entries are shared, QoS actions is unique on each target.
For example:
class-map c1
match ip any
QoS Actions Numbers of Entries Supported
Classification 64 K input and 64 K output classification entries are supported.
A given policy can use at most 24 K ACLs.
Policing 16 K policers are supported. Policers are allocated to given direction in blocks of 2 K.
For example, 2 K policers can be used in for input and 14 K policers can be used for
output. single-rate policers uses one policer entry. Single Rate Three Color Marker
(srTCM) (RFC 2697) and Two Rate Three Color Marker (trTCM) (RFC 2698) uses
two policer entries.
Marking Marking of CoS and DSCP/Precedence is supported through two marking tables, each
capable of supporting 512 entries. Separate tables exist for each direction.
Queuing The queue size is configurable with the maximum number of entries configurable
per-port depending on the chassis and line card type.
DBL You can enable DBL action on all configured class maps.