Mls Qos Trust - Cisco Catalyst 2950 Command Reference Manual

Chapter 2 Cisco IOS Commands

mls qos trust

Use the mls qos trust interface configuration command to configure the port trust state. Ingress traffic
can be trusted, and classification is performed by examining the class of service (CoS) or the
Differentiated Services Code Point (DSCP) value. Use the no form of this command to return a port to
its untrusted state.
Syntax Description
cos
cos pass-through
dscp
device cisco-phone (Optional) Classify ingress packets by trusting the value sent from the Cisco IP
dscp
Defaults
The port is not trusted.
Pass-through mode is disabled.
Trusted boundary is disabled.
If no keyword is specified and the switch is running the EI, the default is dscp.
Command Modes Interface configuration
Command History Release
12.1(6)EA2
12.1(11)EA1
Usage Guidelines
Packets entering a quality of service (QoS) domain are classified at the edge of the QoS domain. When
the packets are classified at the edge, the switch port within the QoS domain can be configured to one
of the trusted states because there is no need to classify the packets at every switch within the domain.
Use this command to specify whether the port is trusted and which fields of the packet to use to classify
traffic.
When a port is configured with trust DSCP and the incoming packet is a tagged non-IP packet, the CoS
value for the packet is set to 0, and the DSCP-to-CoS map is not applied. For an untagged non-IP packet,
the default port CoS value is used.
78-11381-05
mls qos trust [cos [pass-through dscp] | device cisco-phone | dscp]
no mls qos trust [cos [pass-through dscp] | device cisco-phone | dscp]
(Optional) Classify ingress packets with packet CoS values. For untagged
packets, the port default CoS value is used.
(Optional) Configure the interface to classify ingress packets by trusting the CoS
value and to send packets without modifying the DSCP value (pass-through
mode).
phone (trusted boundary).
(Optional) Classify ingress packets with packet DSCP values (most significant 6
bits of the 8-bit service-type field). For non-IP packets, the packet CoS value is
set to 0. This keyword is available only if your switch is running the enhanced
software image (EI).
Modification
This command was first introduced.
The device cisco-phone and pass-through dscp keywords were added.
Catalyst 2950 Desktop Switch Command Reference
mls qos trust
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