Cisco Systems 4500 Configuring the Trust State of Interfaces

37-48
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 37 Configuring Quality of Service
Configuring QoS on Supervisor Engines II-Plus, II+10GE, IV, V, V-10GE, 4924, 4948, and 4948-10GE
Configuring the Trust State of Interfaces
This command configures the trust state of interfaces. By default, all interfaces are untrusted.
To configure the trust state of an interface, perform this task:
When configuring the trust state of an interface, note the following:
• You can use the no qos trust command to set the interface state to untrusted.
• For traffic received on an ingress interface configured to trust CoS using the qos trust cos command,
the transmit CoS is always the incoming packet CoS (or the ingress interface default CoS if the
packet is received untagged).
• When the interface trust state is not configured to trust dscp using the qos trust dscp command, the
security and QoS ACL classification always use the interface DSCP and not the incoming packet
DSCP.
• Starting with Cisco IOS Release 12.2(31)SG, the Supervisor Engine V-10GE allows you to classify
a packet based on the packet’s IP DSCP value irrespective of the port trust state. Packet transmit
queuing is not impacted by this behavior. For information on transmit queues, refer to the
“Configuring Transmit Queues” section on page 37-50.”
This example shows how to configure Gigabit Ethernet interface 1/1 with the trust cos keywords:
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)# interface gigabitethernet 1/1
Switch(config-if)# qos trust cos
Switch(config-if)# end
Switch#
This example shows how to verify the configuration:
Switch# show qos interface gigabitethernet 1/1 | include trust
Trust state: trust COS
Switch#
Command Purpose
Step 1 Switch(config)# interface {vlan vlan_ID |
{fastethernet | gigabitethernet} slot/interface |
Port-channel number}
Selects the interface to configure.
Step 2 Switch(config-if)# [no] qos trust [dscp | cos]Configures the trust state of an interface.
Use the no keyword to clear a configured value and
return to the default.
Step 3 Switch(config-if)# end Exits configuration mode.
Step 4 Switch# show qos Verifies the configuration.