Assigning a DSCP policy for a global IP-Diffserv classifier

The preceding section describes how to forward an 802.1p priority level set by an edge (or upstream) switch. This section describes how to use a global IP-Diffserv classifier to mark matching packets with a new DSCP policy. A DSCP policy consists of a DSCP codepoint and an associated 802.1p priority.

You can use a global IP-Diffserv classifier to mark a DSCP policy at the same time with a global IP-Diffserv classifier that marks an 802.1p priority if different DSCP codepoints are configured with each classifier.

To use a global IP-Diffserv classifier to mark matching packets with a new DSCP policy, follow these steps:

  1. Identify the DSCP used to set a policy in packets received from an upstream or edge switch.
  2. Create a new policy by using the qos dscp-map code-point priority 0 - 7 command to configure an 802.1p priority for the codepoint you will use to overwrite the DSCP that the packet carries from upstream.
  3. Use the qos type-of-service diff-services incoming-DSCP dscp outgoing-DSCP command to change the policy on packets coming from the edge or upstream switch with the specified incoming DSCP.

    The figure in Assigning an 802.1p priority for a global IP-diffserv classifier illustrates this scenario.

Example process:

qos type-of-service diff-services

Enables ToS Diff-serve QoS so that Diff-serve policy configurations can be applied to incoming packets that have matching codepoints.


qos type-of-service diff-services current-codepoint dscp new-codepoint

Configures the switch to select an incoming IP packet carrying the current-codepoint and then use the new-codepoint to assign a new, previously configured DSCP policy to the packet. The policy overwrites the current-codepoint with the new-codepoint and assigns the 802.1p priority specified by the policy.

Valid values for a DSCP codepoint are as follows:
  • 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 (hexadecimal) name for a binary DSCP bit set Enter ? to display the list of valid codepoint entries.To reconfigure the 802.1p priority currently assigned to a DSCP codepoint, use the qos dscp-map command.


no qos type-of-service

Disables all ToS classifier operation. Current ToS DSCP policies and priorities remain in the configuration and will become available if you re-enable ToS Diff-services.


no qos type-of-service [diff-services codepoint]

Deletes the DSCP policy assigned to the codepoint and returns the codepoint to the 802.1p priority setting it had before the DSCP policy was assigned, which is either a value from 0 - 7 or No-override.


show qos type-of-service

Displays a listing of codepoints with any corresponding DSCP policy reassignments for outbound packets. Also displays the 802.1p priority for each codepoint that does not have a DSCP remarking policy assigned to it. See the Viewing the current DSCP-map configuration example below.

  • Determine if the DSCP codepoints that you want to use to mark matching packets already have an 802.1p priority assigned, which could indicate use by existing applications (show qos dscp-map command). This is not a problem as long as the configured priorities are acceptable for all applications using the same DSCP.

  • Also, note that 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).
    Viewing the current DSCP-map configuration
  • Configure the desired policies (codepoint and associated 802.1p priority) in the DSCP table:
    Configuring DSCP policies in the DSCP table
    switch(config)# qos dscp-map 000010 priority 6 name 'Level 6'
    switch(config)# qos dscp-map 000101 priority 4 name 'Level 4'
    switch(config)# show qos dscp-map
      DSCP -> 802.p priority mappings
      DSCP policy 802.1p tag Policy name
      ----------- ---------- -----------------
      000000      No-override
      000001      No-override
      000010      6          Level 6
      000011      No-override
      000100      No-override
      000101      4          Level 4
      000110      No-override
      000111      No-override
  • Assign the new policies to mark matching packets with the specified codepoints.
    Assigning DSCP policies to outbound packets based on the DSCP codepoint from upstream devices

Configuring new DSCP policies

The following example shows how to configure new DSCP policies on matching packets with the specified DSCP codepoints.

Received DSCP

Policy DSCP

802.1p Priority

Policy Name (Optional)




Level 6




Level 4