PRTG Manual: SNMP Custom Table Sensor

Table OID

Enter the object identifier (OID) of the SNMP table that you want to monitor. The OID needs to point directly to an object that represents an SNMP table. Once you have created the sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, add the sensor anew.

Without entering an OID, you cannot proceed with sensor channel creation.

Sensor Name

Enter a meaningful name to identify the sensor. You can use the placeholders [tablename] and [rowidentifier]. They are replaced with the name of the table and the identifying value of the chosen row respectively. You can select the column that provides the row identifier in the Identification Column option below.

You can also enter a valid OID that is part of a different SNMP table, for example, [1.3.6.1.2.1.2.2.1.2], to query information that is not contained in the current table. The same index as in the original table is added to the OID.

Table

Select the relevant table rows in which you find the data that you want to monitor. You see a list with the names of all items that you can monitor. Add check marks in front of the respective lines to select the desired items. You can also use the check box in the table header to select all items or cancel the selection.

PRTG creates one sensor for each selection.

PRTG shows you the table that the OID you entered before returns. To better find what you want to monitor, particularly in large tables, use the search function in the upper-right corner.

Identification Column

Define the identification column for the SNMP Custom Table sensors that you want to create. The sensor uses this column to uniquely identify each table row. This column should preferably be unique because it allows the sensor to keep track of changing indexes.

The value of the column that you selected as identification column replaces the [rowidentifier] in the sensor name. This lets you distinguish sensors that are created for the same SNMP table.

One new sensor is created for each table row that you select.

Sensor Channel #2 – #10

You can create up to 10 different sensor channels for this sensor. You have to define at least one data channel, so you see all available settings for Sensor Channel #1 without enabling it manually. Additionally, you can define Sensor Channel #2 up to Sensor Channel #10. To do so, choose between:

• Disable: The sensor does not create this channel.
• Enable: Create an additional channel and define all its characteristics below, its name, column, value type, and unit.

It is not possible to enable or disable sensor channels after creating this sensor.

All sensor channels that you define while creating an SNMP Custom Table sensor are the same for all sensors for each table row.

Value Type

Select the expected type of results in this channel:

• Absolute (unsigned integer): For integer values, such as 10 or 120.
• Absolute (signed integer): For integer values, such as -12 or 120.
• Absolute (float): For float values, such as -5.80 or 8.23. This value type is not compatible with the unit Value Lookup.
• Delta (Counter): For counter values, PRTG calculates the difference between the last and the current value. The delta value is additionally divided by a time period to indicate a speed value. This value type is not compatible with the unit Value Lookup.

See below for other channel settings that you can also change after sensor creation.

This sensor monitors numerical values only. Make sure that you do not select columns that return strings because they lead to a Down status. For example, if you monitor an ifTable, we recommend that you do not select an ifDescr column because this results in an error.

Sensor Name

Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.

Parent Tags

Shows tags that this sensor inherits from its parent device, group, and probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited. You can add additional tags to the sensor.

It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. A sensor with a top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

Table OID

Shows the OID of the SNMP table that this sensor monitors. Once you have created the sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, add the sensor anew.

Identifier

This is the value of the column that you selected as the Identification Column during sensor creation. It is also displayed in the sensor name to distinguish it from other sensors you created for the same table with other table rows. You can change the identifier if you want to.

Identification Column

Shows the table column that you chose as identification column. Once you have created the sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, add the sensor anew.

Sensor Channel #x Name

Enter a name for the channel in which the sensor shows the desired result. Enter a string.

Sensor Channel #x Column

Select the table column that together with the table row points to the value that you want to monitor in this channel. You can choose between the available columns of the table that you monitor.

Sensor Channel #x Value Type

Shows the value type of the data that this sensor receives in this channel. Once you have created the sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, add the sensor anew.

Sensor Channel #x Unit

Define the unit of the data that this sensor receives in this channel:

• BytesBandwidth
• BytesMemory
• BytesDisk
• Temperature
• Percent
• TimeResponse
• TimeSeconds
• TimeHours
• Count
• CPU
• BytesFile
• SpeedDisk
• SpeedNet
• Custom
• Value Lookup

For more information about available units, see section Custom Sensors.

To use lookups with this channel, select Value Lookup and define the lookup file in Sensor Channel #x Value Lookup. Do not use the unit Custom for using lookups with this sensor and do not use the channel settings to define a lookup file.

Using the unit Value Lookup is not possible when you select the value type Delta (counter) or Absolute (float). You are not able to create the sensor in this case.

Sensor Channel #x Custom Unit

This setting is only visible if you select the Custom unit option above. Define a unit for the channel value. Enter a string.

Sensor Channel #x Value Lookup

This setting is only visible if you select the Value Lookup option above. Select a lookup file that you want to use with this channel.

Sensor Channel #x+1

Shows if you enabled or disabled a channel. Once you have created the sensor, you cannot change this value. It is shown for reference purposes only. If you need to change this value, add the sensor anew.

Primary Channel

Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.

You can set a different primary channel later by clicking the pin symbol of a channel on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

• Show channels independently (default): Show a graph for each channel.
• Stack channels on top of each other: Stack channels on top of each other to create a multi-channel graph. This generates a graph that visualizes the different components of your total traffic.
  This option cannot be used in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This field is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours). The scanning interval determines the amount of time that the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Define the number of scanning intervals that the sensor has time to reach and check a device again in case a sensor query fails. Depending on the option that you select, the sensor can try to reach and check a device again several times before the sensor shows a Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows a Warning status. Choose from:

• Set sensor to down immediately: Set the sensor to a Down status immediately after the first failed request.
• Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to a Warning status after the first failed request. If the following request also fails, the sensor shows an error.
• Set sensor to warning for 2 intervals, then set to down: Set the sensor to a Down status only after three consecutively failed requests.
• Set sensor to warning for 3 intervals, then set to down: Set the sensor to a Down status only after four consecutively failed requests.
• Set sensor to warning for 4 intervals, then set to down: Set the sensor to a Down status only after five consecutively failed requests.
• Set sensor to warning for 5 intervals, then set to down: Set the sensor to a Down status only after six consecutively failed requests.

Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show a Down status. It is not possible to immediately set a WMI sensor to a Down status, so the first option does not apply to these sensors. All other options can apply.

If you define error limits for a sensor's channels, the sensor immediately shows a Down status. No "wait" option applies.

If a channel uses lookup values, the sensor immediately shows a Down status. No "wait" options apply.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days or hours) every week.

You can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.

Schedules are generally inherited. New schedules are added to schedules that you already set up, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a maintenance window, the selected object and all child objects are not monitored. They are in a Paused status instead. Choose between:

• Not set (monitor continuously): No maintenance window is set and monitoring is always active.
• Set up a one-time maintenance window: Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for an active maintenance window.

To terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:

• Use parent: Use the dependency type of the parent object.
• Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in a Down status or in a Paused status caused by another dependency.

• Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in a Down status, the device is paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor is paused if the parent group is paused by another dependency.

To test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This field is only visible if you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This field is only visible if you enable Select a sensor above. Define a time span in seconds for dependency delay.

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects is additionally delayed by the defined time span. This can prevent false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.

This setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

User Group Access

Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:

• Inherited: Inherit the access rights settings of the parent object.
• No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
• Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
• Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
• Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

For more details on access rights, see section Access Rights Management.