Managing Configuration Files Configuration Guide, Cisco IOS Release 15M&T
Configuration Generation Performance Enhancement
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Configuration Generation Performance Enhancement

The Configuration Generation Performance Enhancement feature assists configuration management by enabling faster collection of running configuration file information. This feature is especially useful in managing large networks with numerous interfaces configured.

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.

Restrictions for Configuration Generation Performance Enhancement

The device on which the Configuration Generation Performance Enhancement feature is used must have enough memory available to store (cache) a large interface configuration file. For example, if the interface configurations take up 15 KB of memory, using this feature would require having an additional 15 KB of memory space available.

The presence of the parser config cache interface command in the module reflects an improvement in the performance of the configured interfaces. There is no such performance improvement observed in modules without any physical interfaces such as the Network Analyzer Module (NAM).

Information About Configuration Generation Performance Enhancement

Cisco IOS Software Configuration Storage

In the Cisco IOS software configuration model, the configuration state is maintained in a distributed manner, with each component storing its own configuration state. To retrieve configuration information, the software must poll every component to collect the distributed information. This configuration state retrieval operation is performed by a process known as nonvolatile generation (NVGEN), and it is used by command-line interface (CLI) commands such as showrunning-config, writememory, and copysystem:running-configuration to display or copy the running system configuration. When invoked, NVGEN queries each system component and each instance of interface or other configuration objects. A running configuration file is constructed as NVGEN traverses the system performing these queries.


Note

If you try to configure the writememory command when a router is low on memory and the backup buffer cannot be allocated, then the command will fail with the error message, “Not enough space.” When the writememory command fails to apply the new configuration, the backup configuration is used to restore the original configuration.

Benefits of the Configuration Generation Performance Enhancement

Before the Configuration Generation Performance Enhancement feature was introduced, NVGEN always had to query the entire system and could generate only a total configuration. The time required to process the running configuration creates performance problems for configuration management, because completion of the NVGEN operation can take many minutes.

The Configuration Generation Performance Enhancement feature reduces the execution time for NVGEN processes and is especially useful for managing large configuration files that contain numerous interface configurations. This feature provides faster execution of commands that process the running system configuration by caching interface configuration information in system memory, and by retrieving only configuration information that has changed.

How to Configure the Configuration Generation Performance Enhancement

Configuring the Configuration Generation Performance Enhancement

Perform this task to enable the Configuration Generation Performance Enhancement.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    parser config cache interface

    4.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 parser config cache interface


    Example:
    Router(config)# parser config cache interface
     

    Reduces the time required for the CLI to execute commands that manage the running system configuration, especially for large configuration files.

     
    Step 4 end


    Example:
    Router(config)# end
     

    Exits global configuration mode and returns to privileged EXEC mode.

     

    Configuration Examples for the Configuration Generation Performance Enhancement

    Configuring the Configuration Generation Performance Enhancement Example

    The following example shows how to enable the Configuration Generation Performance Enhancement feature:

    Router(config)# parser config cache interface

    Verifying the Configuration Generation Performance Enhancement Example

    You can verify that the parserconfigcacheinterface command has been enabled by checking for the command in the system configuration file displayed when you enter the showrunning-configuration EXEC command.


    Note

    The first time you display the configuration file, you will not see much evidence of improvement in performance because the interface cache will be filled up. However, you will notice performance improvements when you enter subsequent NVGEN-type commands such as the showrunning-config EXEC command. Each time the interface configuration changes, the cache of the specified interface is flushed. The other interface data remains cached as before. Entering an NVGEN-type command after modifying the interface configuration will once again not show much evidence of improvement until the next NVGEN-type command is entered.

    Router# show running-config
!
!
parser config cache interface
!
!

    Additional References

    The following sections provide references related to the Configuration Generation Performance Enhancement feature.

    Related Documents

    Related Topic

    Document Title

    Cisco IOS commands

    Cisco IOS Master Commands List, All Releases

    System configuration file management commands

    The Cisco IOS Configuration Fundamentals Command Reference appropriate to your software release.

    System configuration file management

    “Managing Configuration Files” module in the Cisco IOS Configuration Fundamentals Configuration Guide

    Standards

    Standards

    Title

    None

    --

    MIBs

    MIBs

    MIBs Link

    None

    To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

    http:/​/​www.cisco.com/​go/​mibs

    RFCs

    RFCs

    Title

    None

    --

    Technical Assistance

    Description

    Link

    The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

    To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

    Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

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

    Feature Information for Configuration Generation Performance Enhancement

    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 the Configuration Generation Performance Enhancement Feature

    Feature Name

    Releases

    Feature Information

    Configuration Generation Performance Enhancement

    12.3(7)T 12.2(25)S 12.2(33)SRC 12.2(33)SB 12.2(33)SXI

    The Configuration Generation Performance Enhancement feature assists configuration management by enabling faster collection of running configuration file information. This feature is especially useful in managing large networks with numerous interfaces configured.

    In 12.2(33)SB, this feature was implemented on the Cisco 10000 series.

    The following command was introduced or modified: parser config cache interface.