Creating a policy based on source-port classifiers

Only one DSCP per source-port may be used to mark matching packets.

Configuring a new DSCP for a source-port automatically overwrites any previous DSCP or 802.1p priority configuration for that source-port classifier.

Procedure
  1. Identify the source-port classifier to which you want to assign a DSCP policy.
  2. Determine the DSCP policy for packets having the selected source-port:

    1. Determine the DSCP you want to assign to the selected packets. (This codepoint will be used to overwrite the DSCP carried in packets received through the source-port from upstream devices.)

    2. Determine the 802.1p priority you want to assign to the DSCP.

  3. If necessary, use the qos dscp-map codepoint priority 0 - 7 command to configure the DSCP policy (codepoint and associated 802.1p priority) that you want to use to mark matching packets.
    NOTE:

    Prerequisite: A DSCP codepoint must have a preconfigured 802.1p priority (0 - 7) before you can use the codepoint to mark matching packets. If a codepoint you want to use shows No-override in the Priority column of the DSCP Policy table (show qos dscp-map command), you must first configure a priority for the codepoint before proceeding (qos dscp-map priority command). 

    qos dscp-map codepoint priority 0 - 7

    This command is optional if a priority has already been assigned to the codepoint .

    The command creates a DSCP policy by assigning an 802.1p priority to a specific DSCP. When the switch applies this priority to a packet, the priority determines the packet's queue in the outbound port to which it is sent. If the packet leaves the switch on a tagged port, it carries the 802.1p priority with it to the next downstream device. For IP packets, the DSCP codepoint in the packet header is replaced by the codepoint specified in this command.

    Default: For most codepoints, No-override. See The default DSCP policy table.

  4. Configure the switch to assign the DSCP policy to packets from the specified source-port. 
    
interface port-list qos dscp codepoint

    Assigns a DSCP policy to IP packets from the specified source-ports, and overwrites the DSCP in these packets with the assigned codepoint value.

    • A binary value for the six-bit codepoint from 000000 to 111111.

    • A decimal value from 0 (low priority) to 63 (high priority) that corresponds to a binary DSCP bit set.

    • An ASCII standard name for a binary DSCP bit set.

    Enter ? to display the list of valid codepoint entries. 

    
interface port-list qos dscp codepoint

    The DSCP policy includes an 802.1p priority and determines the packet's queue in the outbound port to which it is sent. If the packet leaves the switch on a tagged port, it carries the 802.1p priority with it to the next downstream device.

    Default: No-override 

    
no interface [e] port-list qos

    Removes a QoS classifier for the specified source-ports. 

    
show qos port

    Displays a listing of all source-port QoS classifiers currently in the running-config file

    Assigning DSCP policies (codepoint and associated 802.1p priority) to packets from the specified source-ports:

    Source-Port

    DSCP

    Priority

    A2

    000111

    7

    B1-B3

    000101

    5

    B4, C2

    000010

    1