Assigning a DSCP policy based on the source-port

This option assigns a previously configured DSCP policy (codepoint and 802.1p priority) to outbound IP packets (received from the specified sourceports). That is, the switch:

Procedure
  1. Selects an incoming IP packet on the basis of its source-port on the switch.
  2. Overwrites the packet’s DSCP with the DSCP configured in the switch for such packets.
  3. Assigns 802.1p priority configured in the switch for the new DSCP (see Differentiated Services Codepoint (DSCP) mapping).
  4. Forwards the packet through the appropriate outbound port queue.

Steps for creating a policy based on source-port classifier:

NOTE:

You can select one DSCP per source-port. Also, configuring a new DSCP for a source-port automatically overwrites (replaces) any previous DSCP or 802.1p priority configuration for that port.)

  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. Configure the DSCP policy by using qos dscp-map to configure the priority for each codepoint (see Differentiated Services Codepoint (DSCP) mapping for more information).

  4. Configure the switch to assign the DSCP policy to packets from the specified source-port.

Syntax: 


interface <port-list> qos dscp <codepoint>

Assigns a DSCP policy to packets from the specified sourceports, and overwrites the DSCP in these packets with the assigned <codepoint> value. This 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)

Syntax: 


no interface <port-list> qos

Removes QoS classifier for the specified source-ports.

Syntax: 


show qos port

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

For example, suppose that you wanted to assign this set of priorities that have been configured on the switch:

Source-port

DSCP

Priority

2

15

7

1, 3

16

5

4, 5

17

1

Assign the DSCP policies to the selected source-ports and display the result.

An example of the completed source-port DSCP-priority configuration is shown below 

switch(config)# int 4,5
switch(eth-4,5)# qos dscp 17
switch(eth-4,5)# int 1,3
switch(eth-1,3)# qos dscp 16
switch(eth-1,3)# int 2
switch(eth-2)# qos dscp 15

switch(eth-2)# show qos port-priority

Port priorities

  Port Apply rule  | DSCP   Priority    Radius Override
  ---- ----------- + ------ ----------- ---------------
  1    DSCP        | 010000 5           No-override
  2    DSCP        | 001111 7           No-override
  3    DSCP        | 010000 5           No-override
  4    DSCP        | 010001 1           No-override
  5    DSCP        | 010001 1           No-override
  6    No-override |        No-override No-override
  7    No-override |        No-override No-override
  .         .         .          .           .
  .         .         .          .           .