Document ID: 60045
Contents
Introduction
Prerequisites
Requirements
Components Used
Conventions
Configure
Configurations
Verify
Troubleshoot
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Introduction
This document provides a sample configuration of DNS probes on the Content Switching Module (CSM). DNS probes are used to query DNS servers for specific domain names. DNS probes check the response against a preconfigured value to determine whether or not the CSM should continue to use the server.
Prerequisites
Requirements
There are no specific requirements for this document.
Components Used
The information in this document is based on the CSM version 3.x or higher .
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Conventions
For more information on document conventions, refer to the Cisco Technical Tips Conventions.
Configure
In this section, you are presented with the information to configure the features described in this document.
Note: To find additional information on the commands used in this document, use the Command Lookup Tool ( registered customers only) .
Configurations
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Content Switching Module |
|---|
module ContentSwitchingModule 4 ! vlan 499 client ip address 192.168.10.97 255.255.254.0 gateway 192.168.10.1 ! probe DNSTEST dns name www.yahoo.com !--- The probe is configured for the CSM to request the IP address !--- associated with the domain name www.yahoo.com. address 216.109.117.107 !--- The expected response is configured as 216.109.117.107. !--- Multiple addresses can be entered. If the response matches any !--- one of the configured address, the server is considered alive. port 53 !--- Configuration of the DNS port is recommended, even if the default port !--- of 53 is being used. ! probe DNSTEST2 dns name www.yahoo.com address 216.109.117.107 !--- To demonstrate the importance of the port command, the same probe !--- as above is used without the port. ! serverfarm DNS1 nat server no nat client real 144.254.10.123 inservice probe DNSTEST ! serverfarm DNS2 nat server no nat client real 144.254.10.123 inservice probe DNSTEST2 !--- This probe has a problem because the CSM cannot determine which port to use. ! serverfarm DNS3 nat server no nat client real 144.254.10.123 53 inservice probe DNSTEST2 !--- This is the same serverfarm as above, but now the CSM can determine which port !--- to use, as specified in the real server definition. ! vserver DNS1 virtual 192.168.1.1 tcp 53 serverfarm DNS1 persistent rebalance inservice ! vserver DNS2 virtual 192.168.1.2 any serverfarm DNS2 persistent rebalance inservice ! vserver DNS3 virtual 192.168.1.3 any serverfarm DNS3 persistent rebalance inservice ! |
Verify
This section provides information you can use to confirm your configuration is working properly.
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show module csm slot probe name NAME detail
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show module csm slot real
This demonstrates that the probe is functioning properly.
cpu0#sho mod csm 4 probe name dnstest det probe type port interval retries failed open receive --------------------------------------------------------------------- DNSTEST dns 53 120 3 300 10 DNS Info: www.yahoo.com DNS Expected IP address: 216.109.117.107 real vserver serverfarm policy status ------------------------------------------------------------------------------ 144.254.10.123:53 DNS1 DNS1 (default) TESTING
As noted in the configuration, it is recommended that the DNS port be configured, even if the default port of 53 is used. This is due to the fact that the CSM does not use a default destination port for the DNS probes. If the CSM cannot determine the port, the probe is not enabled.
This command output is an example of what is displayed when the CSM fails to determine the destination port for the probe. Packets are not being sent. In this state, the CSM does not mark the service down, but instead stays operational; the problem might go undetected.
cpu0#sho mod csm 4 probe name dnstest2 det probe type port interval retries failed open receive --------------------------------------------------------------------- DNSTEST2 dns 120 3 300 10 DNS Info: www.yahoo.com DNS Expected IP address: 216.109.117.107 real vserver serverfarm policy status ------------------------------------------------------------------------------ 144.254.10.123:53 DNS3 DNS3 (default) FAILED 144.254.10.123:0 DNS2 DNS2 (default) ???
Also, notice that the probe DNSTEST2, when associated with serverfarm DNS2, has a status of ???. This is because the CSM failed to determine the destination port to use for sending the probes. In serverfarm DNS3, the real server port is specified; there were no problems running the probes.
cpu0#sho mod csm 4 real real server farm weight state conns/hits ------------------------------------------------------------------------- 144.254.10.123 DNS1 8 PROBE_FAILED 0 144.254.10.123 DNS2 8 OPERATIONAL 0 144.254.10.123:53 DNS3 8 PROBE_FAILED 0
When the probe fails to run (indicated by a status of ???), the real server remains operational.
Troubleshoot
There is currently no specific troubleshooting information available for this configuration.
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Related Information
- Configuring the Content Switching Module
- Content Switching Module Hardware Support
- Cisco Cat 6000 Other Intelligent Module SW Downloads
- Technical Support - Cisco Systems
| Updated: Sep 07, 2004 | Document ID: 60045 |