By default, OpManager provides numerous SNMP monitors that can be used to monitor the health and performance of your SNMP-based network devices, and to track them in real-time. But in case these monitors do not meet your requirements, OpManager also provides you with an option to create custom SNMP monitors to get performance metrics based on vendor specific OIDs provided in the MIB.
Custom SNMP monitors can be added using several methods:
Initially, we need to input the desired OID(s) and ensure that a valid response is returned by querying a device. The steps involved are as follows:
This option helps you test the OID against a device. The monitor will not be associated to the selected device.
Next, provide the required SNMP OID(s) in the Choose SNMP OID field. You can either directly input the OIDs if you know them already, or you can use the built-in MIB browser to browse and select the OIDs by clicking on the "Choose OID" button.
The Choose SNMP OID field is not limited to just containing the OID. It also provides options for the user to construct OID expressions that perform simple mathematical operations on the output values of the OID. You can also construct expressions by combining OIDs.
Currently, these are the expressions that are supported - Addition (+), Subtraction(-). Multiplication(*), Division (/), Modulus (%) and Max/Min operations (max(a,b) / min(a,b). Note that whenever you are providing OIDs anywhere in OpManager, they must always start with a period. (Example: .a.b.c.d.e.f.g.h)
Functional Expressions allow you to set a predefined format on the display parameters of an output value.
E.g. In the case of adding an SNMP monitor to fetch the CPU temperature value, you can use a functional expression to convert Celsius to Fahrenheit. It also supports aggregate methods that allow you to perform operations which combine multiple values to give a single output. E.g. AverageOfColumnValues, SumOfColumnValues etc.
Use the drop-down menu to select a vendor to which you want to associate the template (or) enter a new vendor name (Click New → Enter a new Vendor Name → Click Add). Now, click Query Device.
This "Query Device" option should be used to check whether the provided OID is giving the expected output value. If not, you need to go back to the OID configuration page and make the necessary changes for it to provide the correct response. Please proceed with the configuration process only after ensuring this.
An Object identifier (OIDs) can sometimes return multiple values, commonly called as Tabular objects. Depending on the OID chosen, the second "Graph details" window might contain more or fewer fields that need to be configured. If you chose an OID that returns a single value (either string or numeric), you can simply check if the response is valid and click "Next".
If you chose an OID that returns multiple values, you need to proceed to configure the other fields as given below:
OpManager provides the option of selecting specific instances that you want to monitor from a Tabular object.
This checkbox the creation of separate SNMP monitors for each instance if multiple instances are available under an OID. If you choose to select this option, it is mandatory that you provide inputs to the Series Index and the Series Display Name fields.
The Series Index and Series Display Name fields are used in OpManager to display the legends for the multi-instance monitor graphs. Using this, you can configure which instances of your OID need to be displayed in your performance graphs.
Note: The Series Index and the Series Display Name drop-down menu will automatically list all the OIDs under the same parent. If the index or description OIDs are not listed, you can type in the required OID.
Monitor Name: Enter your preferred monitor name. The default name will be the OID name.
Interval (Mins): This value specifies the time interval in which you want to re-run the monitor to fetch the corresponding values.
Units: Specify the unit for the monitored resource.
Store Data: If you select Counter type OIDs, you can store data in two ways - the delta value (difference between last poll value and current poll value) or the absolute value (value obtained during every poll stored as such). By default, OpManager stores data using the delta value. However, you can use the Store Data drop-down to select your preference.
Data Type: The options available under the Data Type field depend on the type of OID selected.
You can check this option to set thresholds on the alerts that will be generated based on this monitor.
Select the condition [>, =, < or !=]for Attention, Trouble & Critical alert thresholds, and enter the values. An alert is raised if the monitored value is greater than, equal to, not equal to, or lesser than the specified threshold value, based on the condition selected.
For string-based thresholds, you can choose from the following conditions - CONTAINS, EQUALS, NOT CONTAINS, NOT EQUALS, MATCH REGEX. You can use these conditions to configure values for all levels of thresholds.
Rearm Value: Enter the Rearm Value for the monitor. A rearm value helps determine if the condition of a monitor has returned to normal after a threshold violation alert.
Example: Let us assume that the attention alert threshold for a memory monitor is configured as, 'Raise Attention alert when the monitored data is > 75' and the monitored memory value of that device exceeds this value, say 80. Then an alert will be raised.
In the next poll, if the monitored memory value is 72, deleting the raised alert might not be the best thing to do since the monitored value is still close to the threshold. This is where the Rearm value comes into play, by allowing you to provide a "reset" value for the monitor. Even if the monitored value gets lower than any of the threshold values, the raised alert is deleted only if the value goes below the Rearm value.
Note: The rearm value must be lesser/greater than the threshold value, based on monitor requirements and the configured threshold condition.
In the Consecutive Times field, enter the value of how many consecutive times the thresholds (Attention, Trouble and Critical) can be violated for an alert to be generated.
Note: If the custom SNMP monitor is created from the Settings page, it will be created as a template. Whereas, if the monitor is created from the Device Snapshot page, it will automatically be associated to that device.