Mls Qos Rewrite Ip Dscp - Cisco Catalyst 3030 Command Reference Manual

Chapter 2 Cisco Catalyst Blade Switch 3030 Cisco IOS Commands

mls qos rewrite ip dscp

Use the mls qos rewrite ip dscp global configuration command to configure the switch to change
(rewrite) the Differentiated Services Code Point (DSCP) field of an incoming IP packet. Use the no form
of this command to configure the switch to not modify (rewrite) the DSCP field of the packet and to
enable DSCP transparency.
Syntax Description This command has no arguments or keywords.
Defaults DSCP transparency is disabled. The switch changes the DSCP field of the incoming IP packet.
Command Modes
Global configuration
Command History Release
12.2(25)SEE
Usage Guidelines
DSCP transparency affects only the DSCP field of a packet at the egress. If DSCP transparency is
enabled by using the no mls qos rewrite ip dscp command, the switch does not modify the DSCP field
in the incoming packet, and the DSCP field in the outgoing packet is the same as that in the incoming
packet.
By default, DSCP transparency is disabled. The switch modifies the DSCP field in an incoming packet,
and the DSCP field in the outgoing packet is based on the quality of service (QoS) configuration,
including the port trust setting, policing and marking, and the DSCP-to-DSCP mutation map.
Regardless of the DSCP transparency configuration, the switch modifies the internal DSCP value of the
packet that the switch uses to generate a class of service (CoS) value representing the priority of the
traffic. The switch also uses the internal DSCP value to select an egress queue and threshold.
For example, if QoS is enabled and an incoming packet has a DSCP value of 32, the switch might modify
the internal DSCP value based on the policy-map configuration and change the internal DSCP value
to 16. If DSCP transparency is enabled, the outgoing DSCP value is 32 (same as the incoming value). If
DSCP transparency is disabled, the outgoing DSCP value is 16 because it is based on the internal DSCP
value.
78-17262-01
mls qos rewrite ip dscp
no mls qos rewrite ip dscp
Modification
This command was introduced.
Cisco Catalyst Blade Switch 3030 Command Reference
mls qos rewrite ip dscp
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