Table Of Contents
Configuration Generation Performance Enhancement
First Published: March 2004Last Updated: March 17, 2010
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 feature information and caveats, see 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 for Configuration Generation Performance Enhancement" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://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
Before enabling the Configuration Generation Performance Enhancement feature, you should understand the following concepts:
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 show running-config, write memory, and copy system: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 write memory 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 write memory 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
This section contains the following procedure:
Configuring the Configuration Generation Performance Enhancement
Perform this task to enable the Configuration Generation Performance Enhancement.
2. configure terminal
3. parser config cache interface
Configuration Examples for the Configuration Generation Performance Enhancement
This section provides the following configuration examples:
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 parser config cache interface command has been enabled by checking for the command in the system configuration file displayed when you enter the show running-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 show running-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!!
The following sections provide references related to the Configuration Generation Performance Enhancement feature.
Related Topic Document Title
Cisco IOS commands
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
MIBs MIBs Link
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
Feature Information for Configuration Generation Performance Enhancement
Table 1 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.
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