The LoadMaster utilizes Layer 3, Layer 4 and Layer 7 health checks to monitor the availability of the Real Servers and the Virtual Services.

Check Interval(seconds)

This field specifies the number of seconds that will pass between consecutive health check attempts and defines the length of the ‘health check cycle’.

Recommended and default value: 9 seconds

Valid values range from the <mininterval> (9) to the <maxinterval> (901).

The <mininterval> is Retry Count * Connect Timeout (seconds) + 1, that is, a maximum value of 9 by default.

The <maxinterval> is 901 [because that is what 60 (maximum Connect Timeout (seconds)) * 15 (maximum Retry Count) + 1 is].

In the WUI, if the value of Check Interval is over 120 (because it is forced to this value by setting the Connect Timeout (seconds) and Retry Count), it cannot be changed by modifying the Check Interval(seconds) drop-down list. To change it, configure the other two options. Otherwise, the maximum value that the interval can be set to is 120.

Connect Timeout (seconds)

This is the allowed maximum wait time for a connection to be established and for the receipt of a reply to a health check. If no reply is received before the timeout expires, then the connection is re-attempted as long as the Retry Count has not been reached. If any HTTP response is received in response to the health check, then no retries are attempted in the current health check cycle.

Default value:4 seconds

Valid values range from 4 to 60.

Retry Count

This specifies the number of times the health check will be re-attempted if the timeout above is reached before receiving a response. To override the global retry count value, you can select any other value from the drop-down list. The retry count does not apply if any response is received in response to the health check. If, for example, either a 200 or a 404 response is received, then no retries are attempted in the current cycle.

Default value: 2

Valid values range from 2 to 15.

In LoadMaster firmware version 7.2.52, the check Interval, Timeout, and Retry Count settings can be configured on each Virtual Service or SubVS. Previously, these were just global settings. For further details, refer to the section Real Servers.