Device and Sensor Setup > Sensor Settings

PRTG Manual: SNMP Library Sensor

The SNMP Library sensor uses a Management Information Base (MIB) file to create sensors that monitor a device via the Simple Network Management Protocol (SNMP).

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 the target device returns based on every object identifier (OID) in the MIB file.

The SNMP Library sensor does not appear as a running sensor. It uses the meta-scan facility of the probe to find or to match OIDs from the MIB file. It is useful because you do not have to manually enter OIDs.

To monitor SNMP-capable devices and to add sensors via 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 contain the OIDs of SNMP counters for the most common network devices.

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.

This sensor has a very low performance impact.

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 Monitor, contact the Paessler support team.

Add Sensor

PRTG shows a list of .oidlib files that are available on the system. This list contains all library files in the \snmplibs subfolder of the PRTG program directory. It contains both the default PRTG library files and your own library files.

List of SNMP Library Files

The library file names in the list indicate their purpose. Select a library file that is suitable for the target device (for example, choose an MIB file that you imported) and confirm via Ok.

If the library file not suitable for the target 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 library file.

The SNMP Library sensor takes a list of OIDs that you import from an MIB file into an .oidlib file and tests the OIDs against the target device to find the OIDs that the target device supports. This discovery process is the meta-scan. If the sensor finds counters for the target device, the sensor settings open with a list of all available monitoring items.

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 counters that you want to monitor and click Save. PRTG creates sensors based on the OID types of the selected counters.

Add Sensor Settings

Setting	Description
Library	Shows the path to the .oidlib file that this sensor uses. PRTG shows this value for reference purposes only. If you need to change this value, add the sensor anew.
Library OIDs	Select the parameters that you want to monitor. The list is specific to your setup. The list contains all counters that are available in the .oidlib file that match the target device. Select one or more items by enabling or disabling the check boxes 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. Depending on the type of the selected entries, PRTG creates the following sensors: SNMP Custom Advanced sensor: For 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. SNMP Custom String sensor: For each selected entry that returns a string value. SNMP Custom Table sensor: For up to 10 channels for 10 columns per row.The channels represent the values in the columns of the same row. Once you create a custom SNMP sensor, you can create a device template from it and prepare it for distribution. For example, you can refine the template with better name templates.

Setting

Description

Library

Shows the path to the .oidlib file that this sensor uses.

PRTG shows this value for reference purposes only. If you need to change this value, add the sensor anew.

Library OIDs

Select the parameters that you want to monitor. The list is specific to your setup. The list contains all counters that are available in the .oidlib file that match the target device. Select one or more items by enabling or disabling the check boxes 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.

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

SNMP Custom Advanced sensor: For 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.
SNMP Custom String sensor: For each selected entry that returns a string value.
SNMP Custom Table sensor: For up to 10 channels for 10 columns per row.The channels represent the values in the columns of the same row.

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

Basic Sensor Settings

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

Basic Sensor 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. If the name contains angle brackets (<>), PRTG replaces them with braces ({}) for security reasons. For more information, see the Knowledge Base: What security features does PRTG include?
Parent Tags	Shows tags that the sensor inherits from its parent device, parent group, and parent probe. This setting is for your information only. You cannot change it.
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 (<>). For performance reasons, it can take some minutes until you can filter for new tags that you added. 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 the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority () to the highest priority ().

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

Sensor Specific

The available sensor settings depend on the sensor that the SNMP Library sensor creates. 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 below a channel gauge 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 setting 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 below a channel gauge 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 setting 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. We recommend that you change them centrally in the root group settings if necessary. To change a setting for this object only, click under the corresponding setting name to disable the inheritance and to display its options.

For more information, see section Inheritance of Settings.

Scanning Interval

Click to interrupt the inheritance.

Scanning Interval

Setting	Description
Scanning Interval	Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from: 30 seconds 60 seconds 5 minutes 10 minutes 15 minutes 30 minutes 1 hour 4 hours 6 hours 12 hours 24 hours You can change the available intervals in the system administration on PRTG on premises installations.
If a Sensor Query Fails	Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to 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 request fails. Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the Warning status after the first request fails. If the second request also fails, the sensor shows the Down status. Set sensor to warning for 2 intervals, then set to down: Set the sensor to the Down status only after the third request fails. Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after the fourth request fails. Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after the fifth request fails. Set sensor to warning for 5 intervals, then set to down: Set the sensor to the Down status only after the sixth request fails. 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. None of the interval options apply. If a channel uses lookup values, the sensor immediately shows the Down status. None of the interval options apply.

Setting

Description

Scanning Interval

Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:

30 seconds
60 seconds
5 minutes
10 minutes
15 minutes
30 minutes
1 hour
4 hours
6 hours
12 hours
24 hours

You can change the available intervals in the system administration on PRTG on premises installations.

If a Sensor Query Fails

Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to 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 request fails.
Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to the Warning status after the first request fails. If the second request also fails, the sensor shows the Down status.
Set sensor to warning for 2 intervals, then set to down: Set the sensor to the Down status only after the third request fails.
Set sensor to warning for 3 intervals, then set to down: Set the sensor to the Down status only after the fourth request fails.
Set sensor to warning for 4 intervals, then set to down: Set the sensor to the Down status only after the fifth request fails.
Set sensor to warning for 5 intervals, then set to down: Set the sensor to the Down status only after the sixth request fails.

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. None of the interval options apply.

If a channel uses lookup values, the sensor immediately shows the Down status. None of the interval options apply.

Schedules, Dependencies, and Maintenance Windows

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 schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.

Schedules, Dependencies, and Maintenance Windows

Setting	Description
Schedule	Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from: None Saturdays Sundays Weekdays Weekdays Eight-To-Eight (08:00 - 20:00) Weekdays Nights (17:00 - 09:00) Weekdays Nights (20:00 - 08:00) Weekdays Nine-To-Five (09:00 - 17:00) Weekends You can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Schedules.
Maintenance Window	Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between: Do not set up a one-time maintenance window: Do not set up a one-time maintenance window. Monitoring is always active. Set up a one-time maintenance window: Set up a one-time maintenance window and pause monitoring. You can define a time span for the pause below. 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 setting 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 one-time maintenance window.
Maintenance Ends	This setting 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 one-time maintenance window.
Dependency Type	Select 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 because of 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 setting is only visible if you enable Select a sensor above. Click and use the object selector to select a sensor on which the current object will depend.
Dependency Delay (Sec.)	This setting is only visible if you enable Select a sensor above. Define a time span in seconds for the dependency delay. After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. 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.

Access Rights

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.

Import MIB Files

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

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

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

PRTG adds the lookups without status 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. For more information, see section Define Lookups.

To import MIB files into PRTG Hosted Monitor, contact the Paessler support team.

Default .oidlib Files Overview

PRTG comes with the following .oidlib files.

The .oidlib files might not support all devices or parameters.

.oidlib File	Description
APC UPS.oidlib	Monitors uninterruptible power supplies (UPSs) from APC American Power Conversion Corp.
APCSensorstationlib.oidlib	Monitors alarm status, communication status, humidity, and temperature as shown by an APC sensor station.
Basic Linux Library (UCD-SNMP-MIB).oidlib	Monitors basic system parameters on Linux systems, such as memory, disk and swap, CPU, and more.
cisco-interfaces.oidlib	Monitors 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	Monitors 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	Monitors Dell storage devices. Possible parameters include disk arrays, battery and power supply, fan and temperature, virtual disk, and more.
Dell Systems Management Instrumentation.oidlib	Monitors 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	Monitors toner, paper, and jam status of an HP LaserJet printer.
Linux SNMP (AX BGP DisMan EtherLike Host).oidlib	Monitors 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 appears.
Linux SNMP (Framework Proxy Noti v2).oidlib	Monitors 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 appears.
Linux SNMP (IP Net SNMP Noti OSPF RMON SMUX).oidlib	Monitors 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 appears.
Linux SNMP (Source TCP UCD UDP).oidlib	Monitors 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 appears.
Paessler Common OID Library.oidlib	Monitors many common hardware devices. It is used for several sensors and is encrypted.
SNMP Informant std.oidlib	Monitors logical disks, processor, memory, and network interface on Windows systems.