Configuration > Quality of Service
The DSCP Policy Table window lets you create a DSCP policy by assigning an 802.1p priority to a codepoint. The DSCP policy will be used to overwrite the DSCP and 802.1p priority carried in packets that meet the criteria of a QoS policy.
To implement a DSCP policy, you must map it to the DSCP (codepoint) contained in incoming IPv4 packet headers and select Differentiated Services as the Type of Service policy.
On 5300xl switches, DSCP policies (codepoint remarking) cannot be applied to outbound IPv4 packets having IP options. On the Series 3400cl and 6400cl switches, mixing ToS DSCP policies and 802.1p priorities is not recommended.
Initially, the DSCP Policy Table lists the switch’s default priority setting for each standard codepoint.
In a few cases, such as 001010 and 001100, a default policy (implied by the DSCP standards for Assured-Forwarding and Expedited-Forwarding) is used. A default DSCP policy is not in effect until you apply the DSCP policy to a QoS classifier or configure a Differentiated Services policy for it.
Identify the QoS classifiers that use the DSCP policy you want to change.
Assign the QoS classifiers identified in step 1 to a different DSCP policy, an 802.1p priority, or No-override.
If a QoS policy is using the DSCP policy, you must delete or change this assignment before you can change the priority setting on the codepoint. Otherwise, the switch blocks the change.
Select Quality of Service from the Configuration tab, and then select DSCP Policy Table from the left pane. The DSCP Policy Table window lists all DSCPs configured in the network.
Select the DSCP you want to change.
Click the Priority drop-down arrow and select the priority you want to assign to the DSCP. Possible values are 0-7 and No Override, which does not prioritize the packet unless another QoS policy creates priority assignments.
If a priority is not assigned, IP packets received through a VLAN-tagged port receive whatever 802.1p priority they carry in the 802.1Q tag in the packet’s header. VLAN-tagged packets received through an untagged port are handled in the switch with normal priority.
If desired, reassign the revised DSCP policy to the QoS policies.
For additional information, refer to the Advanced Traffic Management Guide for your switch.