OpManager allows you to create custom SNMP monitors to get performance metrics based on vendor specific OIDs provided in the MIB.
i. OID Browser
ii. Upload MIB
Go to Settings → Monitoring → Performance Monitors → Add (or) Inventory → Device Snapshot Page → Monitors → Performance Monitors → Actions → Add monitor.
To add an SNMP monitor, you need to first provide the OID based on which OpManager will fetch data related to the required metric from a device.
1. Choose SNMP OID:
You can either enter the OID for which you want to add a monitor/ select an OID from the OID browser.
To access the OID browser, click Choose OID.
Step 1: Select MIB
In the drop-down menu provided on the top-left corner of the OID browser, you can select the MIB file from which you want to select the SNMP OID. You can find a list of default/ supported MIBs included in this drop-down.
If you do not find a suitable MIB, you can also upload a MIB provided by your vendor using the UploadMIB option.
I) Click Upload MIB.
ii) Browse and Upload a vendor provided MIB file.
Note: Please upload MIBs with RFC2578 MIB Standard to avoid parsing errors.
Step 2: Select OID
Search OID/Name: The OID browser in OpManager allows you to search the MIB for OIDs using the object identifier/name (.188.8.131.52.184.108.40.206/ sysUpTime). You can also browse and select the required OID directly from the MIB tree.
Step 3: Test OID
Once you have selected an OID from the MIB tree, you will be able to view the OID, its Syntax and its Description. You can now test the OID to check if the output is desirable by clicking TestOID. This option allows you to review an OID's output, even before adding it to the expression.
Step 4: Now, click Choose OID. This will insert the selected OID into the Choose SNMP OID field.
2. Performing operations on OIDs using expressions:
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.
Restrictions on OID expressions:
If more than one Multiple Instance OID is present in the expression, then it should be of the same parent node.
Monitor involving both Scalar and Multiple OIDs are not supported.
Monitor involving both String and Numeric OIDs are not supported.
You cannot use string monitors to create expressions.
You cannot add Table OIDs as a Monitor.
3. Functional Expression
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.
4. Device Name
This option helps you test the OID against a device. The template will not get associated to the selected device.
5. Vendor Name
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.
Object identifiers (OIDs) have both a type and a value. It is on this basis that they are classified into Scalar Objects and Tabular Objects. A scalar object is a managed object that always has a single instance, whereas, tabular objects have multiple instances. In both these cases, the output can either be a string or a numerical value.
i) Scalar Objects:
1. Scalar objects with a numerical output will display a table containing the instance and the value along with a graph.
2. Scalar objects with a string output will only display the instance and the value.
ii) Tabular Objects:
1. Tabular objects with a numerical output will display a table containing the instance and the value along with a graph.
2. Tabular objects with a string output will only display the instance and the value.
OpManager provides the option of selecting specific instances that you want to monitor from a tabular object.
All Instances: A single SNMP monitor that monitors multiple instances will be created.
Do you wish to create each instance as an individual monitor?
This checkbox creates a separate SNMP monitor for each instance.
If you choose to select this option, it is mandatory that you provide inputs to the Series Index and the Series Display Name fields.
Series Index & Series Display Name
Series Index: An index is used to refer to a particular instance of a tabular object. A tabular object can have one or more instances and is identified by its index value. To identify a specific columnar variable, the index of the row has to be appended to its OID.
Series Display Name: This corresponds to the description/ name/ label that should be associated to an instance.
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.
1. Monitor Name: Enter your preferred monitor name. The default name will be the OID name.
2. Interval (Mins): This value specifies the time interval in which you want to re-run the monitor to fetch the corresponding values.
3. Units: Specify the unit for the monitored resource.
4. Data Type: Select between 'Integer' and 'Decimal' depending on the data type required.
5. Do you want to enable Threshold for this monitor?
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 value. An alert is raised if the monitored value is greater than, equal to, not equal to, or lesser than (which ever is selected) the specified threshold value.
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.
Enter the Rearm Value. 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. An alert will be raised.
In the next poll, if the monitored memory value is 72. Another alert will be generated, stating that the device is in a normal condition.
Now, if in the next poll, the monitored value climbs to 80. A threshold violation alert will again be generated which becomes troublesome to manage.
A rearm value helps avoid this hassle by confirming that a device has returned to normal, only if the monitored value matches 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.
5. Click Add Monitor.
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.
Counter Type OIDs
If you select Counter type OIDs, you can store data based on the delta value or the absolute value. By default, OpManager stores data using the delta value. However, you can use the Store Data drop-down to select your preference.