Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure Quality of Service for Outbound Traffic

QoS VLAN-ID (VID) Priority

QoS Classifier Precedence: 5

The QoS protocol option enables you to use up to 256 VLAN-IDs as QoS classifiers. Where a particular VLAN-ID classifier has the highest precedence in the switch for traffic in that VLAN, then traffic received in that VLAN is marked with the VID classifier’s configured priority level. Different VLAN-ID classifiers can have differing priority levels.

Options for Assigning Priority. Priority control options for packets carry­ ing a specified VLAN-ID include:

802.1p priority

DSCP policy (Assigning a new DSCP and an associated 802.1p priority; inbound packets must be IPv4.)

(For operation when other QoS classifiers apply to the same traffic, refer to “Classifiers for Prioritizing Outbound Packets” on page 15-8.)

N o t e

QoS with VID priority applies to static VLANs only, and applying QoS to

 

dynamic VLANs created by GVRP operation is not supported. A VLAN must

 

exist while a subject of a QoS configuration, and eliminating a VID from the

 

switch causes the switch to clear any QoS features configured for that VID.

 

 

Assigning a Priority Based on VLAN-ID Only

This option assigns a priority to all outbound packets having the specified VLAN-ID (VID). You can configure this option by either specifying the VLAN­ ID ahead of the qos command or moving to the VLAN context for the VLAN you want to configure for priority.

Syntax: vlan < vlan-id> qos priority < 0 - 7 >

Configures an 802.1p priority for outbound packets belong­ ing to the specified VLAN. This priority determines the packet’s queue in the outbound port to which it is sent. If the packet leaves the switch in a tagged VLAN, it carries the 802.1p priority with it to the next downstream device. You can configure one QoS classifier for each VLAN-ID. (Default: No-override)

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