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Quality of Service: Managing Bandwidth More Effectively
Globally-Configured QoS
If you later decided to remove VLAN 20 from QoS prioritization, you would
enter the following command:
In this instance, No- override
indicates that VLAN 20 is not
prioritized by QoS.
Figure 6-24. Returning a QoS-Prioritized VLAN to “No-override” Status
Assigning a DSCP Policy for a Global VLAN-ID Classifier
This global QoS packet-marking option assigns a previously configured DSCP
policy (codepoint and 802.1p priority) to outbound IP packets having the
specified VLAN-ID (VID). The switch:
1. Selects an incoming IP packet on the basis of the VLAN-ID it carries.
2. Overwrites the packet’s DSCP with the DSCP configured for matching
packets.
3. Assigns the 802.1p priority associated with the new DSCP. (See “Differen-
tiated Services Codepoint (DSCP) Mapping” on page 6-88.)
4. Forwards the packet through the appropriate outbound port queue.
Creating a Policy Based on VLAN-ID Classifier.
1. Determine the VLAN-ID classifier to which you want to assign a DSCP
policy.
2. Determine the DSCP policy for packets carrying the selected VLAN-ID:
a. Determine the DSCP you want to assign to the selected packets. (This
codepoint will be used to overwrite the DSCP carried in packets
received from upstream devices.)
b. Determine the 802.1p priority you want to assign to the DSCP.
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