Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure Quality of Service for Outbound Traffic

N o t e

A codepoint must have an 802.1p priority (0 - 7) before you can configure the

 

codepoint for use in prioritizing packets by VLAN-ID. If a codepoint you want

 

to use shows No-overridein the Priority column of the DSCP Policy table (show

 

qos dscp-map), then assign a priority before proceeding.

 

4. Configure the switch to assign the DSCP policy to packets with the

 

 

specified VLAN-ID.

 

Syntax: qos dscp-map < codepoint > priority < 0 - 7 >

 

This command is optional if a priority has already

 

been assigned to the < codepoint >. The command creates

 

a DSCP policy by assigning an 802.1p priority to a

 

specific DSCP. When the switch applies this priority to

 

a packet, the 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. If the

 

packet is IPv4, the packet’s DSCP will be replaced by the

 

codepoint specified in this command. (Default: For

 

most codepoints, No-override. See figure 15-8on page

 

15-52.)

 

Syntax: vlan < vid > qos dscp < codepoint >

 

Assigns a DSCP policy to packets carrying the specified

 

IP address, 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 in a tagged VLAN, it

 

carries the 802.1p priority with it to the next down-

 

stream device. (Default: No-override)

 

no vlan < vid > qos

 

Removes QoS classifier for the specified VLAN.

 

show qos device-priority

 

Displays a listing of all QoS VLAN-ID classifiers cur-

 

rently in the running-config file.

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