Configuring Priority Queueing

This module describes the tasks for configuring priority queueing (PQ) on a device.

A priority list contains the definitions for a set of priority queues. The priority list specifies which queue a packet will be placed in and, optionally, the maximum length of the different queues.

In order to perform queueing using a priority list, you must assign the list to an interface. The same priority list can be applied to multiple interfaces. Alternatively, you can create many different priority policies to apply to different interfaces.

Assign packets to priority queues based on the following qualities:

  • Protocol type

  • Interface where the packets enter the device

You can specify multiple assignment rules. The priority-list commands are read in order of appearance until a matching protocol or interface type is found. When a match is found, the packet is assigned to the appropriate queue and the search ends. Packets that do not match other assignment rules are assigned to the default queue.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

How to Configure Priority Queueing

Defining the Priority List

Assigning Packets to Priority Queues

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    priority-list list-number protocol protocol-name {high | medium | normal | low} queue-keyword keyword-value

    4.    priority-list list-number interface interface-type interface-number {high | medium | normal| low}

    5.    priority-list list-number default {high | medium | normal | low}

    6.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Device> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 priority-list list-number protocol protocol-name {high | medium | normal | low} queue-keyword keyword-value


    Example:
    Device(config)# priority-list 1 protocol ip high list 10
     

    Establishes queueing priorities based on the protocol type.

    Note   

    All protocols supported by Cisco are allowed. The queue-keyword argument provides additional options including byte count, TCP service and port number assignments, and AppleTalk, IP, IPX, VINES, or XNS access list assignments. Refer to the priority-list protocol command syntax description in the Cisco IOS Quality of Service Solutions Command Reference.

     
    Step 4 priority-list list-number interface interface-type interface-number {high | medium | normal| low}


    Example:
    Device(config)# priority-list 3 interface ethernet 0 medium
     

    Establishes queueing priorities for packets entering from a given interface.

     
    Step 5 priority-list list-number default {high | medium | normal | low}


    Example:
    Device(config)# priority-list 3 default high
     

    Assigns a priority queue for those packets that do not match any other rule in the priority list.

     
    Step 6 end


    Example:
    Device(config)# end
     

    Exits global configuration mode and returns to privileged EXEC mode.

     

    Specifying the Maximum Size of the Priority Queues

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    priority-list

      4.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Device> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Device# configure terminal
       

      Enters global configuration mode.

       
      Step 3 priority-list


      Example:
      Device(config)# policy-list
       

      Specifies the maximum number of packets allowed in each of the priority queues:

      • high-limit--20

      • medium-limit--40

      • normal-limit--60

      • low-limit--80

       
      Step 4 end


      Example:
      Device(config)# end
       

      (Optional) Exits global configuration mode.

       

      Assigning the Priority List to an Interface

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    interface interface-type interface-number

        4.    priority-group list-number

        5.    end


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Device> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 configure terminal


        Example:
        Device# configure terminal
         

        Enters global configuration mode.

         
        Step 3 interface interface-type interface-number


        Example:
        Device(config)# interface ethernet 0
         

        Specifies the interface, and then enters interface configuration mode.

         
        Step 4priority-group list-number


        Example:
        Device(config-if)# priority-group 3
         

        Assigns a priority list number to the interface.

         
        Step 5 end


        Example:
        Device(config-if)# end
         

        Exits interface configuration mode and returns to privileged EXEC mode.

         

        Monitoring Priority Queueing Lists

        SUMMARY STEPS

          1.    enable

          2.    show queue interface-type interface-number

          3.    show queueing priority


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Device> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 show queue interface-type interface-number


          Example:
          Device# show queue interface-type interface-number
           

          Displays the contents of packets inside a queue for a particular interface or VC.

           
          Step 3 show queueing priority


          Example:
          Device# show queueing priority
           

          Displays the status of the priority queueing lists.

           

          Configuration Examples for Priority Queueing

          Example: Priority Queueing Based on Protocol Type

          The following example establishes queueing based on protocol type. The example assigns 1 as the arbitrary priority list number, specifies IP as the protocol type, and assigns a high-priority level to traffic that matches IP access list 10. 

          access-list 10 permit 239.1.1.0 0.0.0.255
priority-list 1 protocol ip high list 10

          Example: Priority Queueing Based on Interface

          The following example establishes queueing based on interface. The example sets any packet type entering on Ethernet interface 0 to a medium priority. 

          priority-list 3 interface ethernet 0 medium

          Example: Maximum Specified Size of the Priority Queue

          The following example changes the maximum number of packets in the high-priority queue to 10. The medium-limit, normal, and low-limit queue sizes remain at their default 40-, 60-, and 80-packet limits. 

          priority-list 4 queue-limit 10 40 60 80

          Example: Priority List Assigned to an Interface

          The following example assigns priority group list 4 to serial interface 0: 

          interface serial 0
  priority-group 4

          Note

          The priority-group list-number command is not available on ATM interfaces that do not support fancy queueing.

          Example: Priority Queueing Using Multiple Rules

          When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol type. The following example specifies four rules:

          • DECnet packets with a byte count less than 200 are assigned a medium-priority queue level.

          • IP packets originating or destined to TCP port 23 are assigned a medium-priority queue level.

          • IP packets originating or destined to User Datagram Protocol (UDP) port 53 are assigned a medium-priority queue level.

          • All IP packets are assigned a high-priority queue level.

          Remember that when using multiple rules for a single protocol, the system reads the priority settings in the order of appearance. 

          priority-list 4 protocol decnet medium lt 200
priority-list 4 protocol ip medium tcp 23
priority-list 4 protocol ip medium udp 53
priority-list 4 protocol ip high

          Additional References for Configuring Priority Queueing

          Related Documents

          Related Topic

          Document Title

          Cisco commands

          Cisco IOS Master Commands List, All Releases

          QoS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

          Cisco IOS Quality of Service Solutions Command Reference

          Technical Assistance

          Description

          Link

          The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

          http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

          Feature Information for Configuring Priority Queueing

          The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

          Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
          Table 1 Feature Information for Configuring Priority Queueing

          Feature Name

          Releases

          Feature Information

          Priority Queueing (PQ)

          11.2(1)

          12.2(27)SBB

          12.2(33)XNA

          Cisco IOS XE Release 3.2SE

          The Priority Queueing (PQ) feature allows you to configure priority queueing on a device with the use of priority lists.

          The following commands were introduced or modified by this feature: priority-group, priority list default, priority list interface, priority list protocol, priority list queue-limit, show queue, show queueing priority.