Trust - Cisco Catalyst 3550 Command Reference Manual

trust

trust
Use the trust policy-map class configuration command to define a trust state for traffic classified by the
class or the class-map command. Use the no form of this command to return to the default setting.
Syntax Description
cos
dscp
ip-precedence
Defaults
The action is not trusted. If no keyword is specified when the command is entered, the default is dscp.
Command Modes Policy-map class configuration
Command History Release
12.1(4)EA1
Usage Guidelines Use this command to distinguish the quality of service (QoS) trust behavior for certain traffic from
others. For example, incoming traffic with certain DSCP values can be trusted. You can configure a class
map to match and trust the DSCP values in the incoming traffic.
Trust values set with this command supersede trust values set on specific interfaces with the mls qos
trust interface configuration command.
The trust command is mutually exclusive with set policy-map class configuration command within the
same policy map.
You cannot use the service-policy interface configuration command to attach policy maps that contain
these elements to an egress interface:
•
•
•
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trust [cos | dscp | ip-precedence]
no trust [cos | dscp | ip-precedence]
(Optional) Classify ingress packets by using the packet class of service (CoS)
values. For untagged packets, the port default CoS value is used.
(Optional) Classify ingress packets by using the packet Differentiated Services
Code Point (DSCP) values (most significant 6 bits of 8-bit service-type field). For
non-IP packets, the packet CoS value is used if the packet is tagged. If the packet
is untagged, the default port CoS value is used to map CoS to DSCP.
(Optional) Classify ingress packets by using the packet IP-precedence values
(most significant 3 bits of 8-bit service-type field). For non-IP packets, the packet
CoS value is used if the packet is tagged. If the packet is untagged, the port default
CoS value is used to map CoS to DSCP.
Modification
This command was first introduced.
set or trust policy-map class configuration commands. Instead, you can use the police policy-map
class configuration command to mark down (reduce) the DSCP value at the egress interface.
Access control list (ACL) classification.
Per-port per-VLAN classification.
Chapter 2 Cisco IOS Commands
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