Cisco Catalyst 3550

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Catalyst 3550 Multilayer Switch Command Reference
OL-8566-02
Chapter 2 Catalyst 3550 Switch Cisco IOS Commands
mls qos trust
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 Differentiated Services Code Point
(DSCP), class of service (CoS), or IP-precedence packet field. Use the no form of this command to
return a port to its untrusted state.
mls qos trust [cos [pass-through dscp] | device cisco-phone | dscp [pass-through cos] |
ip-precedence]
no mls qos trust [cos [pass-through] | device | dscp [pass-through] | ip-precedence]
Syntax Description
Defaults The port is not trusted. If no keyword is specified when the command is entered, the default is dscp.
Command Modes Interface configuration
Command History
cos (Optional) Classify ingress packets with packet CoS values. For untagged
packets, use the port default CoS value.
cos pass-through
dscp
(Optional) Classify ingress packets by trusting the CoS value and by sending
packets without modifying the DSCP value (pass-through mode).
device cisco-phone (Optional) Classify ingress packets by trusting the CoS or DSCP value sent
from the Cisco IP Phone (trusted boundary), depending on the trust setting.
dscp (Optional) Classify ingress packets with packet DSCP values (most significant
6 bits of 8-bit service-type field). For non-IP packets, the packet CoS is used
if the packet is tagged. The default port CoS value is used if the packet is
untagged.
dscp pass-through
cos
(Optional) Classify ingress packets by trusting the DSCP value and by sending
packets without modifying the CoS value (pass-through mode).
ip-precedence (Optional) Classify ingress packets with IP-precedence values (most
significant 3 bits of 8-bit service-type field). For non-IP packets, the packet
CoS is used if the packet is tagged. The port default CoS value is used if the
packet is untagged.
Release Modification
12.1(4)EA1 This command was introduced.
12.1(11)EA1 The device cisco-phone, pass-through cos, and pass-through dscp
keywords were added.
12.1(20)EA2 The usage guidelines were revised to describe how the switch sets the trust
state when a Cisco IP Phone is connected to a switch or routed port.