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9-8

Catalyst 6500 Series Content Switching Module Configuration Note

OL-4612-01

Chapter 9 Configuring Health Monitoring

Configuring HTTP Return Code Checking

Note Retries are the number of abnormal end sessions that the CSM will tolerate before removing a real server

from service. The failed time is the number of seconds which the CSM waits before reattempting a

connection to a real server that was removed from service by inband health checking.

This example shows how to enable inband health monitoring for a server farm named geo:

Router(config-module-csm)# serverfarm geo

Router(config-slb-sfarm)# health retries 43 failed 160

Configuring HTTP Return Code Checking

These sections describe HTTP return code checking:

• Understanding HTTP Return Code Checking, page 9-8

• Configuring HTTP Return Code Checking, page 9-9

Understanding HTTP Return Code Checking

The return error code checking (return code parsing) feature is used to indicate when a server is not

returning web pages correctly. This feature extends the capability of CSM to inspect packets, parse the

HTML return codes, and act upon the return codes returned by the server.

After receiving an HTTP request from the CSM, the server responds with an HTTP return code. The

CSM can use the HTTP return error codes to determine the availability of the server. The CSM can be

configured to take a server out of use in response to receiving specific return codes.

A list of predefined codes (100 through 599) are in RFC 2616. For return code checking, some codes are

more usable than others. For example, a return code of 404 is defined as a URL not found, which may

be the result of the user entering the URL incorrectly. Error code 404 also might mean that the web server

has a hardware problem, such as a defective disk drive preventing the server from finding the data

requested. In this case, the web server is still alive, but the server cannot send the requested data because

of the defective disk drive. Because of the inability of the server to return the data, you do not want future

requests for data sent to this server. To determine the error codes you want to use for return code

checking, refer to RFC 2616.

When HTTP return code checking is configured, the CSM monitors HTTP responses from all balanced

HTTP connections and logs the occurrence of the return code for each real server. The CSM stores return

code counts. When a threshold for a return code is reached, the CSM may send syslog messages or

remove the server from service.

A default action, counting return codes, syslog messaging, or removing the real server from service or a

set of these actions can be applied to a server farm. You also can bind a single virtual group to multiple

server farms allowing you to reuse a single return code server farm policy on multiple server farms.

Note When you configure HTTP return code checking on a virtual server, the performance of that virtual

server is impacted. Once return code parsing is enabled, all HTTP server responses must be parsed for

return codes.

Cisco Catalyst 6500 Series Configuration Note

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