Configuring Interface level QoS Trust DSCP

QoS trust dscp is applicable for L2 Switch Port only. Trust DSCP can be enabled on physical interface after configuring Switch Port. After QoS Trust DSCP is enabled on Switch port, a user configured DSCP-to-traffic class map can be applied on the Switch Port interface.

If the IP header is present for incoming packet that is getting L2 forwarded, then traffic class is selected for this packet will be based on IP DSCP. If the IP header not present, then VLAN PCP for tagged packet, and Interface Level traffic-class config for untagged packet will be used for traffic class selection.

Follow these steps to configure an interface QoS Trust DSCP.

1. Enter the global configuration mode.
   

   SLX # configure terminal 
   SLX (config)# 

2. Enter interface configuration mode.
   

   SLX (config)# interface ethernet 0/2
   SLX (conf-if-eth-0/2)# 

3. Configure the QoS traffic-class per interface.
   

   SLX (conf-if-eth-0/2)# qos trust dscp
   SLX (conf-if-eth-0/2)# 

4. Return to privileged exec mode
   

   SLX (conf-if-eth-0/2)# end
   SLX #

5. Verify your configuration using the show qos interface eth 0/2 command.
   

   SLX #show qos interface eth 0/2
   Interface Ethernet 0/2
   Trust CoS : True    Remark CoS : False
         Trust DSCP: True    Remark DSCP: False
       Default TC: 0 
6. Save the Running Configuration file to the Startup Configuration file.
   

   SLX #copy running-config startup-config
   SLX #

This example shows the above steps in a consolidated format:

SLX # configure terminal
SLX (config)# interface ethernet 0/2
SLX (conf-if-eth-0/2)# qos trust dscp
SLX (conf-if-eth-0/2)# end
SLX # show qos interface eth 0/2
SLX # copy running-config startup-config