Quality of Service (QoS): Managing Bandwidth More Effectively

Using QoS Classifiers To Configure QoS for Outbound Traffic

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 on a tagged port, it carries the 802.1p priority with it to the next downstream 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 currently in the running-config file.

For example, suppose you wanted to assign this set of priorities:

VLAN-ID

DSCP

Priority

40

000111

7

30

000101

5

20

000010

1

1

000010

1

 

 

 

1.Determine whether the DSCPs already have priority assignments, which could indicate use by existing applications. This is not a problem as long as the configured priorities are acceptable for all applications using the same DSCP. (Refer to the “Note On Changing a Priority Setting” on page 6-61.Also, a DSCP must have a priority configured before you can assign any QoS classifiers to use it.)

The DSCPs for this example have not yet been assigned an 802.1p priority level.

Figure 6-25. Display the Current Configuration in the DSCP Policy Table

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