Select the minimum and maximum value, if you need them, and the logical operator . The result definition section will be displayed on value axis - red fields determines value section where warning is sent as soon as determined value is exceeded. You can define a time period that will be used for the calculation of the arithmetic mean of the values measured. This value will be used as a reference value for comparison with the set values. An alert will be sent to the groups specified, which are the same as the groups of contacts defined for Nagios.

You can use variables in the subject and body of messages to make emails and SMS clearer. All alerts are sent through the mail-manager, so they are managed with the help of a mail queue (the queue can be displayed in Statistics Emails). These notifications have the highest priority, so they are sent first.

When adding a new alert, you have to enter the following details: the name of an alert, the kind of event being reported, a time limit, the minimum and maximum value including an operator, the groups of contacts to send a given notification to (email, SMS, PUSH) and the text of the notification itself, in which you can use variables (their list is displayed at the bottom of the page). The value entered in the Time limit field specifies how long a given characteristic has to be within the set interval for an alert notification to be sent. Example: You have set the system to send you alerts when the Wi-Fi signal strength drops below 15 dBm. The value in the Time limit field specifies how long the Wi-Fi signal strength has to be below 15 dBm for an alert to be sent.

It sometimes happened that the system did not retrieve the value of a certain characteristic (for example: voltage on a MikroTik router). As a result, “0” was saved to the DB RRD. This value was then included in the calculation of the arithmetic mean. At one point, the voltage was 12V. At another, it was 0V. This led to the average value being skewed (6V). Consequently, an alert was triggered. When you are creating/editing an alert, there is the following option: Include Null Values in Calculation. This option allows you to set whether you want “false outages and null values” to be included or not in the calculation of the average. The average value is null only if all values measured within a given timeframe are null too.