Quality of Service (QoS): Managing Bandwidth More Effectively

Preparation for Configuring QoS

Viewing the QoS Configuration

The following show commands are available on the switches covered in this guide. Examples of the show qos output are included with the example for each priority type.

Syntax: show qos < priority-classifier > dscp-map

Show mappings between DSCP policy and 802.1p pri- ority.

port-priority

Displays the current source-port priority configura- tion. Refer to figure 5-11 on page 5-28.

type-of-service

Displays the current type-of-service priority configu- ration. The display output differs according to the ToS option used:

IP Precedence: Refer to figure 5-3 on page 5-16.

Diffserve: Refer to figure 5-5 on page 5-19.

No Override

By default, the IP ToS, Protocol, and (source) port show outputs automatically list No-overridefor priority options that have not been configured. This means that if you do not configure a priority for a specific option, QoS does not prioritize packets to which that option applies, resulting in the No override state. In this case, 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.

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