Mls Qos - Cisco Catalyst 3750 Command Reference Manual

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands

mls qos

Use the mls qos global configuration command on the switch stack or on a standalone switch 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.
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 DSCP and 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 and egress queue settings are in effect.
Command Modes Global configuration
Command History Release
12.1(11)AX
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.
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.
Examples This example shows how to enable QoS on the switch:
Switch(config)# mls qos
You can verify your settings by entering the show mls qos privileged EXEC command.
78-16181-03
mls qos
no mls qos
Modification
This command was introduced.
Catalyst 3750 Switch Command Reference
mls qos
2-195