2-275
Catalyst 3750 Metro Switch Command Reference
OL-9645-10
Chapter 2 Catalyst 3750 Metro Switch Cisco IOS Commands
mls qos
mls qos
Use the
mls qos
global configuration command to enable quality of service (QoS) for the entire switch.
When the
mls qos
command is entered, QoS is enabled with the default parameters on all ports in the
system. Use the
no
form of this command to reset all the QoS-related statistics and to disable the QoS
features for the entire switch.
mls qos
no mls qos
Syntax Description
This command has no arguments or keywords.
Defaults
QoS is disabled. There is no concept of trusted or untrusted ports because the packets are not modified
(the CoS, DSCP, and IP precedence values in the packet are not changed). Traffic is switched in
pass-through mode (packets are switched without any rewrites and classified as best effort without any
policing).
When QoS is enabled with the
mls qos
global configuration command and all other QoS settings are set
to their defaults, traffic is classified as best effort (the Differentiated Services Code Point [DSCP) and
class of service [CoS] value is set to 0) without any policing. No policy maps are configured. The default
port trust state on all ports is untrusted. The default ingress queue, egress queue-set, and hierarchical
egress queue settings are in effect.
Command Modes
Global configuration
Command History
Usage Guidelines
QoS must be globally enabled to use QoS classification, policing, mark down or drop, queueing, and
traffic shaping features. You can create a policy map and attach it to a port before entering the
mls qos
command. However, until you enter the
mls qos
command, QoS processing is disabled.
Policy maps and class maps used to configure QoS are not deleted from the configuration by the
no mls
qos
command, but entries corresponding to policy maps are removed from the switch hardware to save
system resources. To re-enable QoS with the previous configurations, use the
mls qos
command.
When QoS is disabled, ingress traffic is switched in pass-through mode, which means packets are
switched without any rewrites and are classified to best effort without any policing.
Toggling the QoS status of the switch with this command modifies (reallocates) the sizes of the queues.
During the queue size modification, the queue is temporarily shut down during the hardware
reconfiguration, and the switch drops newly arrived packets for this queue.
Release
Modification
12.1(14)AX
This command was introduced.