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Table Of Contents
DistributedDirector Configurable Cache
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Configuring the Size of the Cache
Configuring How Long the System Retains Sorting Information
Verifying DistributedDirector Cache Information
Configuring the Size of the Cache Example
Configuring How Long the System Retains Sorting Information Example
DistributedDirector Configurable Cache
Feature History
This document describes the DistributedDirector Configurable Cache feature in Cisco IOS Release 12.2(8)T. It includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
DistributedDirector maintains an internal cache of entries that is dynamically configurable. This internal configurable cache consists of sorting events that occur on a per-client basis. Users can configure both the size of this internal cache and the amount of time for which the DistributedDirector system will retain per-client sorting information.
The DistributedDirector Configurable Cache feature allows users to configure their systems in order to limit the amount of memory that DistributedDirector uses for Domain Name System (DNS) caching. When a query that is a duplicate of a previous query comes from the client within the cache timeout period, the same response can be produced without the use of any Director Response Protocol (DRP) queries or sorting.
The DistributedDirector Cache Auto Refresh feature works in the background to continuously update all entries in the DistributedDirector cache. Once this background refresh feature is initiated, DistributedDirector periodically updates all expired cache entries. The DistributedDirector cache saves the latest answers to all past DNS queries received since cache auto refresh was initiated, and any repeat request is served directly from the cache when caching is enabled.
Benefits
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Related Features and Technologies
DistributedDirector Cache Auto Refresh
Related Documents
DistributedDirector Cache Auto Refresh, Cisco IOS Release 12.2(8)T feature module
Supported Platforms
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Determining Platform Support Through Cisco Feature Navigator
Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Cisco Feature Navigator is a web-based tool that enables you to quickly determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.
Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:
Supported Standards, MIBs, and RFCs
Standards
No new standards are supported by this feature.
MIBs
No new MIBs are supported by this feature.
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new RFCs are supported by this feature.
Prerequisites
The sorting cache must be enabled on DistributedDirector. To enable the sorting cache, use the ip director cache command.
Configuration Tasks
See the following sections for configuration tasks for this feature. Each task in the list is identified as either required or optional.
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Configuring the Size of the Cache
To configure the variable size of the DistributedDirector cache, use the following commands in global configuration mode:
Configuring How Long the System Retains Sorting Information
To configure how long the DistributedDirector system will retain per-client sorting information, use the following command in global configuration mode:
Verifying DistributedDirector Cache Information
To show DistributedDirector cache information, use the show ip director cache command.
Router# show ip director cacheDirector cache is onCache current size = 2 maximum size = 2000Cache time for sort cache entries:60 secsDirector sort cache hits = 8Entries:www.myserver.org:for client 172.143.2.78, used 3 times, valid for:00:00:42server 172.21.34.10, rank 0, priority 0random incomplete:0DRP route lookup external to AS incomplete:0administrative preference incomplete:0DRP route lookup internal to AS complete:40DRP distance to associated server incomplete:0portion incomplete:0Round-trip time from DRP to client incomplete:0DFP originated weight incomplete:0Route-map evaluation incomplete:0Boomerang evaluation incomplete:0server 172.21.34.10, rank 0, priority 0, bestrandom incomplete:0DRP route lookup external to AS incomplete:0administrative preference incomplete:0DRP route lookup internal to AS complete:30DRP distance to associated server incomplete:0portion incomplete:0Round-trip time from DRP to client incomplete:0DFP originated weight incomplete:0Route-map evaluation incomplete:0Boomerang evaluation incomplete:0www.boom1.com:for client 172.143.2.78, used 5 times, valid for:00:00:13server 172.21.34.10, rank 0, priority 0random incomplete:0DRP route lookup external to AS incomplete:0administrative preference incomplete:0DRP route lookup internal to AS complete:40DRP distance to associated server incomplete:0portion incomplete:0Round-trip time from DRP to client incomplete:0DFP originated weight incomplete:0Route-map evaluation incomplete:0Boomerang evaluation incomplete:0server 172.21.34.10, rank 0, priority 0, bestrandom incomplete:0DRP route lookup external to AS incomplete:0administrative preference incomplete:0DRP route lookup internal to AS complete:30DRP distance to associated server incomplete:0portion incomplete:0Round-trip time from DRP to client incomplete:0DFP originated weight incomplete:0Route-map evaluation incomplete:0Boomerang evaluation incomplete:0Configuration Examples
This section provides the following configuration examples:
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Configuring the Size of the Cache Example
The following example configures the maximum number of cache entries:
Router(config)# ip director cache size 1500Cache size shrinked to 1500Router# show running-configip host myhost 172.2.2.10 172.2.2.20 172.2.2.30...ip director host myhostip dns primary myhost soa myhost myhost@comno ip director drp synchronizedip director cache size 1500Configuring How Long the System Retains Sorting Information Example
The following example configures how long the DistributedDirector system will retain per-client sorting information:
Router(config)# ip director cache time 100Router# show running-configip host myhost 172.2.2.10 172.2.2.20 172.2.2.30...ip director host myhostip dns primary myhost soa myhost myhost@comno ip director drp synchronizedip director cache time 100Command Reference
This section documents new commands. All other commands used with this feature are documented in the Cisco IOS Release 12.2 command reference publications.
ip director cache size
To configure the variable size of the DistributedDirector cache, use the ip director cache size command in global configuration mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
ip director cache size entries
no ip director cache size entries
Syntax Description
Defaults
Maximum number of cache entries: 2000
Command Modes
Global configuration
Command History
Usage Guidelines
Use the ip director cache size command to configure the maximum number of cache entries that the DistributedDirector system will retain in its cache. This cache size is the maximum number of cache entries that are displayed when the user enters the show ip director cache command.
Examples
The following example configures the maximum number of cache entries:
Router(config)# ip director cache size 1500Cache size shrinked to 1500Router# show ip director cacheDirector cache is onCache current size = 0 maximum size = 1500Cache time for sort cache entries: 60 secsDirector sort cache hits = 0Related Commands
ip director cache time
To configure how long the DistributedDirector system will retain per-client sorting information, use the ip director cache time command in global configuration mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
ip director cache time seconds
no ip director cache time seconds
Syntax Description
seconds
How long the per-client sorting information is retained, in number of seconds. Range is from 1 to 2147483.
Defaults
60 seconds
Command Modes
Global configuration
Command History
Usage Guidelines
Use the ip director cache time command to specify how long the DistributedDirector system will retain per-client sorting in its cache. This cache time is the maximum amount of cache time displayed when the user enters the show ip director cache command.
Examples
The following example configures how long the DistributedDirector system will retain per-client sorting information:
Router(config)# ip director cache time 100Router# show ip director cacheDirector cache is onCache current size = 0 maximum size = 2000Cache time for sort cache entries: 100 secsDirector sort cache hits = 0Related Commands
ip director cache
Enables the sorting cache on DistributedDirector.
ip director cache size
Configures the variable size of the DistributedDirector cache.