Device and Sensor Setup > Sensor Settings

PRTG Manual: SNMP Library Sensor

The SNMP Library sensor uses a compiled Management Information Base (MIB) file to create sensors that monitor a device via the Simple Network Management Protocol (SNMP). This approach provides custom monitoring beyond the standard SNMP sensors of PRTG.

The content of the MIB file determines which data types are available for monitoring. When you create the sensor, it provides a list of counters that came back from the target device based on checking every object identifier (OID) in the MIB file. From this list, you can select what you want to monitor.

The SNMP Library sensor automatically creates the following custom SNMP sensors based on the data types available in the MIB file:

SNMP Custom Advanced sensors for all OIDs that return single values
SNMP Custom String sensors for all OIDs that return string values
SNMP Custom Table sensors for all OIDs that return tables

The SNMP Library sensor is not actually a sensor and does not appear as a running sensor. It is a sensor that uses the meta-scan facility of the probe to find or match OIDs from the compiled MIB file and makes the creation of custom sensors easier because you do not have to manually enter the OIDs.

To monitor SNMP-capable devices and add sensors using the SNMP Library sensor, download the manufacturer's MIB files for the target device, convert the MIB files to the OID library format, and import them into PRTG. PRTG also provides precompiled .oidlib files that already contain the OIDs of SNMP counters for the most common devices in a network.

For more information, see the Knowledge Base: How do SNMP, MIBs and OIDs work?

SNMP Custom Advanced Sensor Created by SNMP Library Sensor

Sensor in Other Languages

Dutch: SNMP Bibliotheek
French: Bibliothèque SNMP
German: SNMP-Bibliothek
Japanese: SNMP ライブラリ
Portuguese: Biblioteca SNMP
Russian: Библиотека SNMP
Simplified Chinese: SNMP 库
Spanish: Biblioteca SNMP

Remarks

This sensor supports the IPv6 protocol.
See the Knowledge Base: How do SNMP, MIBs and OIDs work?
See the Knowledge Base: How can I import my MIB files into PRTG?

See the Knowledge Base: Can't find a sensor for my device in PRTG but I believe it supports SNMP. How to proceed?

To import MIB files into PRTG hosted by Paessler, contact the Paessler support team.

Add Sensor

Manually add a new sensor to an SNMP device. From the Add Sensor dialog, select SNMP Library sensor. PRTG shows a list of .oidlib files that are available on the system. This list contains all library files stored in the \snmplibs subfolder of the PRTG program directory. It contains both the ones delivered with PRTG and your own files.

List of SNMP Library Files

The file names in the list indicate the respective purpose. Select a name that appears suitable for your device (for example, choose an MIB file that you imported before) and confirm via OK. Often, the Paessler common oid library.oidlib is a good start.

If the file does not fit to your device, this results in the error message The scan for available monitoring items has failed on this device: No such object (SNMP error # 222). If you see this message, click Cancel and try to add the sensor with a different file.

The SNMP Library sensor takes a list of OIDs that you imported from an MIB file into an .oidlib file and tests the OIDs against a device to find the OIDs the device supports. This discovery process is the meta-scan. If counters are found for your device, the sensor settings open with a list of available monitoring items that you can select. PRTG sorts the list in advance to make the related values sequential in the list.

List of SNMP Single Values: Sorted by MIB, Category, Name

List of SNMP Table Values: Sorted by MIB, Category (Table Name/OID), Row, Name

The list of SNMP table values sequentially presents row values to help you find the values you are interested in.

You can also use the search function to find the desired group or category. The search matches individual strings, so if your string has a space in it, put the search string in quotes.

Select the desired counters and click Save. PRTG now creates sensors based on the OID types of the selected entries.

For selected SNMP single values, PRTG creates SNMP Custom Advanced sensors with up to 10 channels for 10 OIDs each. For example, 22 selected single values result in 3 sensors: 2 sensors with 10 channels and 1 sensor with 2 channels.
If you select OIDs that return string values, PRTG creates one SNMP Custom String sensor for each selected entry that returns a string value.
For selected SNMP table entries, PRTG creates SNMP Custom Table sensors with up to 10 channels for 10 columns per row.

Once a custom SNMP sensor has been created, you can create a device template from it and prepare it for distribution. For example, you can refine the template with better name templates.

Default .oidlib Files Overview

The following files are included in PRTG and allow the extension of your SNMP monitoring to many devices. Note that the libraries might not support all devices and/or parameters.

.oidlib File	Description
APC UPS.oidlib	Can be used to monitor uninterruptible power supplies (UPS) from APC American Power Conversion Corp.
APCSensorstationlib.oidlib	Can be used to monitor alarm status, communication status, humidity, and temperature as shown by an APC sensor station.
Basic Linux Library (UCD-SNMP-MIB).oidlib	Can be used to monitor basic system parameters on Linux systems, such as memory, disk and swap, CPU, and more.
cisco-interfaces.oidlib	Can be used to monitor Cisco-specific parameters, for example, the number of present network interfaces on a system, several states of an interface (admin, oper, speed, type, errors, discards, etc.), and more.
cisco-queue.oidlib	Can be used to monitor queues on a Cisco interface, for example, queue depth and its maximum, discarded messages from the queue, the number of the queue within the queue set, and more.
Dell Storage Management.oidlib	Can be used to monitor Dell storage devices. Possible parameters include disk arrays, battery and power supply, fan and temperature, virtual disk, and more.
Dell Systems Management Instrumentation.oidlib	Can be used to monitor the hardware of Dell systems. Possible parameters include ACPower and battery, alerts, base board, BIOS, Baseboard Management Controller (BMC), chassis, COO, cooling, event log, firmware, integrated development environment (IDE), keyboard, memory, port, network, processor, Small Computer System Interface (SCSI), system, temperature, USB, universally unique identifier (UUID), and more.
HP LaserJet Status.oidlib	Can be used to monitor toner, paper, and jam status of an HP LaserJet printer.
Linux SNMP (AX BGP DisMan EtherLike Host).oidlib	Can be used to monitor different aspects of Linux systems. This file might detect a very large number of interfaces. It might take a few seconds until the selection table is shown.
Linux SNMP (Framework Proxy Noti v2).oidlib	Can be used to monitor different aspects of Linux systems. This file might detect a very large number of interfaces. It might take a few seconds until the selection table is shown.
Linux SNMP (IP Net SNMP Noti OSPF RMON SMUX).oidlib	Can be used to monitor different aspects of Linux systems. This file might detect a very large number of interfaces. It might take a few seconds until the selection table is shown.
Linux SNMP (Source TCP UCD UDP).oidlib	Can be used to monitor different aspects of Linux systems. This file might detect a very large number of interfaces. It might take a few seconds until the selection table is shown
Paessler Common OID Library.oidlib	Can be used to monitor many common hardware devices. It is used for several sensors and is encrypted.
SNMP Informant std.oidlib	Can be used to monitor logical disks, processor, memory, and network interface on Windows systems.

Import MIB Files

Additionally, you can create your own .oidlib files by importing your device manufacturers' MIB files with the free MIB Importer tool. You can convert your MIB files and save the resulting .oidlib files to the \snmplibs subfolder of the PRTG program directory.

For more information about the MIB Importer and to download this tool, see the Knowledge Base: How can I import my MIB files into PRTG?

If your imported .oidlib file contains lookups (you can see this in section Lookup in the MIB Importer), you can define your own sensor states for returning values. Add an SNMP Library sensor using this .oidlib file. PRTG then creates a lookup definition file using the lookupname of the chosen library as id parameter.

Note: The lookups are added without state definitions, so the sensor shows the Warning status by default. You have to edit the corresponding lookup files to get reliable alarms. Override the lookup definition with your own custom lookup as described in section Define Lookups.

To import MIB files into PRTG hosted by Paessler, contact the Paessler support team.

Add Sensor Settings

The following settings in the Add Sensor dialog differ in comparison to the sensor's Settings tab.

SNMP Library Specific

Setting	Description
Library	Shows the path to the .oidlib file selected before. This setting is shown for your information only and cannot be changed here.
Library OIDs	Select the parameters of the device that you want to monitor. A list specific to your setup is shown. It contains all counters found in the chosen library that match your device. Select one or more items by adding a check mark in front of the respective line. You can also select all items or cancel the selection by using the check box in the table header. Use the search box to narrow down to your desired items. Depending on the kind of the selected entries, PRTG creates the following sensors: SNMP Custom Advanced sensor: One sensor for every 10 single values SNMP Custom String sensor: One sensor for each selected entry that returns a string value SNMP Custom Table sensor: One sensor for each selected table row with up to 10 channels representing values in the columns of the same row

Setting

Description

Library

Shows the path to the .oidlib file selected before. This setting is shown for your information only and cannot be changed here.

Library OIDs

Select the parameters of the device that you want to monitor. A list specific to your setup is shown. It contains all counters found in the chosen library that match your device.

Select one or more items by adding a check mark in front of the respective line. You can also select all items or cancel the selection by using the check box in the table header. Use the search box to narrow down to your desired items.

Depending on the kind of the selected entries, PRTG creates the following sensors:

SNMP Custom Advanced sensor: One sensor for every 10 single values
SNMP Custom String sensor: One sensor for each selected entry that returns a string value
SNMP Custom Table sensor: One sensor for each selected table row with up to 10 channels representing values in the columns of the same row

Basic Sensor Settings

Click the Settings tab of a sensor to change its settings.

Usually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.

Setting	Description
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 the 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. It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>). The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor: snmplibrarysensor
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).Enter topic text here.

Sensor Specific

The available sensor settings depend on the sensor that the SNMP Library sensor created. For details about settings, see the sections of these sensors:

Sensor Display

Setting	Description
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. You cannot use this option 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.

Setting

Description

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.
You cannot use this option 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.

Inherited Settings

By default, all of the following settings are inherited from objects that are higher in the hierarchy. You should change them centrally in the root group settings if necessary. To change a setting for this object only, disable the inheritance by clicking the button next to inherit from under the corresponding setting name. You then see the options described below.

For more information, see section Inheritance of Settings.

Scanning Interval

Click to interrupt the inheritance.

Setting	Description
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 the 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 the Warning status. Choose from: Set sensor to down immediately: Set the sensor to the Down status immediately after the first failed request. Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the 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 the Down status only after three consecutively failed requests. Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after four consecutively failed requests. Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after five consecutively failed requests. Set sensor to warning for 5 intervals, then set to down: Set the sensor to the 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 the Down status. It is not possible to immediately set a WMI sensor to the 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 the Down status. No "wait" option applies. If a channel uses lookup values, the sensor immediately shows the Down status. No "wait" options apply.

Setting

Description

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 the 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 the Warning status. Choose from:

Set sensor to down immediately: Set the sensor to the Down status immediately after the first failed request.
Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the 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 the Down status only after three consecutively failed requests.
Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after four consecutively failed requests.
Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after five consecutively failed requests.
Set sensor to warning for 5 intervals, then set to down: Set the sensor to the 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 the Down status. It is not possible to immediately set a WMI sensor to the 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 the Down status. No "wait" option applies.

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

Schedules, Dependencies, and Maintenance Window

You cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional settings here. They are active at the same time as the parent objects' settings.

Setting	Description
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 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 the 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 the Down status or in the 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 the 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 the 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.

Access Rights

Click to interrupt the inheritance.

Setting	Description
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.

Setting

Description

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.

KNOWLEDGE BASE