- Cisco IOS Network Management Configuration Guide, Release 12.4
Table Of Contents
DistributedDirector Enhancements for Cisco IOS Release 12.1(5)T
Supported Standards, MIBs, and RFCs
Configuring Enhanced Fault Tolerance with Multiple Resource Records
Configuring Event Recording with Syslog
Configuring Enhanced Server Verification with Multiple Port Connect Tests
Verifying Enhanced Fault Tolerance with Multiple Resource Records
Verifying Event Recording with Syslog
Verifying Enhanced Server Verification with Multiple Port Connect Tests
Enhanced Fault Tolerance with Multiple Resource Records Example
Event Recording with Syslog Example
Enhanced Server Verification with Multiple Port Connect Tests Example
DistributedDirector Enhancements for Cisco IOS Release 12.1(5)T
Note
Effective with Cisco IOS Release 12.4(24)T, this feature is not available in Cisco IOS software.
This feature module describes the DistributedDirector Enhancements for Cisco IOS Release 12.1(5)T feature and includes the following sections:
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Feature Overview
The DistributedDirector Enhancements for Cisco IOS Release 12.1(5)T feature consists of the following modified features for the DistributedDirector, which were introduced in Cisco IOS Release 11.1(28)IA:
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The DistributedDirector Enhancements for Cisco IOS Release 12.1(5)T feature also consists of several unrelated new commands. These commands can be found in the Command Reference section.
Enhanced Fault Tolerance with Multiple Resource Records
Before this enhancement, DistributedDirector would return a single Resource Record (RR) in each Domain Name System (DNS) response. A single RR is normally sufficient, but for some applications, server failover will occur more rapidly when applications are provided IP addresses of multiple servers.
The Enhanced Fault Tolerance with Multiple Resource Records feature enables DistributedDirector to return multiple RRs. The number of RRs returned in a single reply is configurable. The default number of RRs returned is one.
Event Recording with Syslog
The Event Recording with Syslog feature enables DistributedDirector to log events by way of the industry-standard syslog system. Server state is logged, providing a useful log of when servers are considered up or down. The logging priority level is notification with priority level five. Additionally, the server selection process, DNS request, and DNS response may be logged. The logging priority level is informational with priority level six.
Enhanced Server Verification with Multiple Port Connect Tests
Before this enhancement, DistributedDirector could evaluate server status by performing a TCP connect test to a single server port. The Enhanced Server Verification with Multiple Port Connect Tests feature allows multiple port connect tests to be specified. If any one of the connect tests fails, the server is considered down.
Benefits
The features provided in Cisco IOS Release 12.1(5)T help make networks that use DistributedDirector more robust. These features ensure that applications have more useful information and perform better server verification, and they allow administrators to track DistributedDirector better. In particular:
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Restrictions
Enhanced Fault Tolerance with Multiple Resource Records
Configuring DistributedDirector to return a large number of records can reduce the benefit of using DistributedDirector to select the best server.
Event Recording with Syslog
Extensive syslog output is provided when logging server selection. Therefore, this feature should not be used when a heavy request load is expected.
Related Documents
For more information on the Cisco DistributedDirector, see the following documents, which are located on Cisco Connection Online (CCO) at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml:
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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 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.
To access Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.
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:
Availability of Cisco IOS Software Images
Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.
Supported Standards, MIBs, and RFCs
Standards
None
MIBs
None
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
None
Configuration Tasks
See the following sections for configuration tasks for this feature. Each task is optional.
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Configuring Enhanced Fault Tolerance with Multiple Resource Records
To configure the Enhanced Fault Tolerance with Multiple Resource Records feature on the DistributedDirector for a host name, use the following command in global configuration mode:
Router(config)# ip director host host-name [a | mx] multiple integer
Configures the number of RRs that the DistributedDirector returns for each DNS response.
Configuring Event Recording with Syslog
To configure the Event Recording with Syslog feature on the DistributedDirector for a host name, use the following commands in global configuration mode:
Configuring Enhanced Server Verification with Multiple Port Connect Tests
To configure the Enhanced Server Verification with Multiple Port Connect Tests feature on the DistributedDirector, use the following commands in global configuration mode:
Verifying Enhanced Fault Tolerance with Multiple Resource Records
To verify that the DistributedDirector is configured to return the best servers for RRs for each DNS, use the show ip director hosts command.
Verifying Event Recording with Syslog
To verify that the DistributedDirector is configured to send to syslog the DNS request and response information, use the show ip director hosts command.
Verifying Enhanced Server Verification with Multiple Port Connect Tests
To verify that the DistributedDirector is configured with a specific connection interval to specified distributed servers, use the show ip director hosts command.
Configuration Examples
This section provides the following configuration examples:
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Enhanced Fault Tolerance with Multiple Resource Records Example
In the following examples, the DistributedDirector is configured to return the best three servers for A resource record on host name www.xyz.com, the best two servers for A resource record on host name alias.xyz.com, and the best two servers for MX resource mail.xyz.com, respectively:
ip director host www.xyz.com multiple 3ip director host alias.xyz.com a multiple 2ip director host mail.xyz.com mx multiple 2Event Recording with Syslog Example
Before configuring the DistributedDirector to syslog events regarding DNS requests on a specific resource record, the following must be typed on the command line:
logging 172.21.34.2logging trap informational
Note
In the following examples, the DistributedDirector is configured to syslog events regarding DNS requests on A resource record for host name www.xyz.com, DNS requests on A resource record for host name alias.xyz.com, and DNS requests on MX host name mail.xyz.com, respectively:
ip director host www.xyz.com loggingip director host alias.xyz.com a loggingip director host mail.xyz.com mx loggingEnhanced Server Verification with Multiple Port Connect Tests Example
In the following example, the DistributedDirector is configured with a connection interval of 5 minutes to distributed servers on port 80 and port 90. The distributed servers will only be considered accessible if both port 80 and port 90 are accessible:
ip director host www.xyz.com connect 80 5ip director host www.xyz.com connect 90 5Command Reference
The following new and modified commands are pertinent to this feature. To see the command pages for these commands and other commands used with this feature, go to the Cisco IOS Master Commands List, Release 12.4, at http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124mindx/
124index.htm.New Commands
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Modified Commands
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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
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