Cisco Catalyst 3550

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Catalyst 3550 Multilayer Switch Command Reference
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Chapter 2 Catalyst 3550 Switch Cisco IOS Commands
trust
The only match criterion in a policy map that can be attached to an egress interface is the match ip dscp
dscp-list class-map configuration command.
If you specify trust cos, QoS derives the internal DSCP value by using the received or default port CoS
value and the CoS-to-DSCP map.
If you specify trust dscp, QoS derives the internal DSCP value by using the DSCP value from the ingress
packet. For non-IP packets that are tagged, QoS derives the internal DSCP value by using the received
CoS value; for non-IP packets that are untagged, QoS derives the internal DSCP value by using the
default port CoS value. In either case, the internal DSCP value is derived from the CoS-to-DSCP map.
If you specify trust ip-precedence, QoS derives the internal DSCP value by using the IP precedence
value from the ingress packet and the IP-precedence-to-DSCP map. For non-IP packets that are tagged,
QoS derives the internal DSCP value by using the received CoS value; for non-IP packets that are
untagged, QoS derives the internal DSCP value by using the default port CoS value. In either case, the
internal DSCP value is derived from the CoS-to-DSCP map.
To return to policy-map configuration mode, use the exit command. To return to privileged EXEC mode,
use the end command.
Examples This example shows how to define a port trust state to trust incoming DSCP values for traffic classified
with class1:
Switch(config)# policy-map policy1
Switch(config-pmap)# class class1
Switch(config-pmap-c)# trust dscp
Switch(config-pmap-c)# police 1000000 20000 exceed-action policed-dscp-transmit
Switch(config-pmap-c)# exit
You can verify your settings by entering the show policy-map privileged EXEC command.
Related Commands Command Description
class Defines a traffic classification for the policy to act on.
police Defines a policer for classified traffic.
policy-map Creates or modifies a policy map that can be attached to multiple
interfaces to specify a service policy.
show policy-map Displays QoS policy maps.