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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 at the end of this module.

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 the Priority List to an Interface

Monitoring Priority Queueing Lists

Defining the Priority List

Assigning Packets to Priority Queues

Specifying the Maximum Size of the Priority Queues

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

Step 1 enable

Enables privileged EXEC mode.

Enter your password if prompted.

Example:

Device> enable

Step 2 configure terminal

Enters global configuration mode.

Example:

Device# configure terminal

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

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.

Example:

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

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

Establishes queueing priorities for packets entering from a given interface.

Example:

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

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

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

Example:

Device(config)# priority-list 3 default high

Step 6 end

Exits global configuration mode and returns to privileged EXEC mode.

Example:

Device(config)# end

Specifying the Maximum Size of the Priority Queues

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    priority-list

4.    end

DETAILED STEPS

Step 1 enable

Enables privileged EXEC mode.

Enter your password if prompted.

Example:

Device> enable

Step 2 configure terminal

Enters global configuration mode.

Example:

Device# configure terminal

Step 3 priority-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

Example:

Device(config)# policy-list

Step 4 end

(Optional) Exits global configuration mode.

Example:

Device(config)# end

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

Step 1 enable

Enables privileged EXEC mode.

Enter your password if prompted.

Example:

Device> enable

Step 2 configure terminal

Enters global configuration mode.

Example:

Device# configure terminal

Step 3 interface interface-type interface-number

Specifies the interface, and then enters interface configuration mode.

Example:

Device(config)# interface ethernet 0

Step 4 priority-group list-number

Assigns a priority list number to the interface.

Example:

Device(config-if)# priority-group 3

Step 5 end

Exits interface configuration mode and returns to privileged EXEC mode.

Example:

Device(config-if)# end

Monitoring Priority Queueing Lists

SUMMARY STEPS

1.    enable

2.    show queue interface-type interface-number

3.    show queueing priority

DETAILED STEPS

Step 1 enable

Enables privileged EXEC mode.

Enter your password if prompted.

Example:

Device> enable

Step 2 show queue interface-type interface-number

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

Example:

Device# show queue interface-type interface-number

Step 3 show queueing priority

Displays the status of the priority queueing lists.

Example:

Device# show queueing priority

Configuration Examples for Priority Queueing

Example: Priority Queueing Based on Protocol Type

Example: Priority Queueing Based on Interface

Example: Maximum Specified Size of the Priority Queue

Example: Priority List Assigned to an Interface

Example: Priority Queueing Using Multiple Rules

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

UnnamedNote

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.