Modular QoS CLI Unconditional Packet Discard
Modular QoS CLI Unconditional Packet Discard
Last Updated: May 17, 2012
This module describes the Modular QoS CLI (MQC) Unconditional Packet Discard feature in Cisco IOS Release 12.2(13)T. It includes the following sections:
Finding Feature Information
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The Modular QoS CLI (MQC) Unconditional Packet Discard feature allows customers to classify traffic matching certain criteria and then configure the system to unconditionally discard any packets matching that criteria. The Modular QoS CLI (MQC) Unconditional Packet Discard feature is configured using the Modular Quality of Service Command-Line Interface (MQC) feature. Packets are unconditionally discarded by using the new drop command within the MQC.
Enhanced System Utilization
This feature allows you to discard (drop), without any further system processing, the packets of a particular class. This function is very useful when you want to discard all the packets for nonessential applications (for instance, Internet browsing applications or unauthorized video applications) and allocate system resources to more essential applications. This feature allows the user to discard those nonessential packets and simultaneously obtain the bit and drop rate statistics for that particular class and the traffic within that class. The statistics are gathered through the CISCO-CLASS-BASED-QOS-MIB.
Packets are unconditionally discarded by configuring the drop action inside a traffic class (inside of a policy map). This drop action is accomplished with the new drop command. Note the following restrictions for configuring the drop action within a traffic class:
Supported Standards MIBs and RFCs
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Configuring the Class Map
Creating a Policy Map
1. Router (config)# policy-mappolicy-name
2. Router (config-pmap)# classclass-name
3. Router (config-pmap)# drop
4. Router(config-cmap)# exit
Attaching the Policy Map to an Interface or a VC
1. Router(config)# interfacetype number [ name-tag
2. Router(config-if)# pvc [name] vpi/vci [ilmi | qsaal | smds]
4. Router(config-if)# exit
Verifying the Discard Action Configuration in the Traffic Class
Example Configuring the Discard Action Configuration in a Traffic Class
In the following sample configuration, a traffic class called "class1" has been created and configured for use in a policy-map called "policy1." The policy-map policy1 is attached to an output serial interface 2/0. All packets matching access-group 101 are placed in a class called "c1." Packets belonging to this class are discarded.
Router(config)# class-map class1 Router(config-cmap)# match access-group 101 Router(config-cmap)# policy-map policy1 Router(config-pmap)# class c1 Router(config-pmap-c)# drop Router(config-pmap-c)# interface s2/0 Router(config-if)# service-policy output policy1 Router(config-if)# exit
The following sample output of the show policy-map command displays the contents of the policy map called "policy1." All the packets belonging to the class called "c1" are discarded.
Router# show policy-map policy1 Policy Map policy1 Class c1 drop
Example Verifying the Discard Action Configuration in the Policy Map
The following sample output of the show policy-map interface command displays the statistics for the Serial2/0 interface, to which a policy map called "policy1" is attached. The discard action has been specified for all the packets belonging to a class called "c1." In this example, 32000 bps of traffic is sent ("offered") to the class and all of them are dropped. Therefore, the drop rate shows 32000 bps.
Router# show policy-map interface Serial2/0 Serial2/0 Service-policy output: policy1 Class-map: c1 (match-all) 10184 packets, 1056436 bytes 5 minute offered rate 32000 bps, drop rate 32000 bps Match: ip precedence 0 drop
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