PRTG Manual: SNMP Library Sensor

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

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

The SNMP Library sensor will automatically create the following custom SNMP sensor types based on the data types available in the MIB:

icon-i-roundThe SNMP Library sensor is not actually a sensor type and will not appear as running sensor. It is a sensor that uses the meta-scan facility of the PRTG probe to find or match OIDs from an MIB and eases the creation of custom sensors, because you do not have to enter the OIDs manually.

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 file to the Paessler oidlib format, and import it into PRTG. To make setting up your monitoring  as convenient as possible, PRTG comes with pre-compiled oidlib library files that already contain the OIDs of SNMP counters for the most common devices in a network.

icon-book-bulbFor more details, see the Knowledge Base: How do SNMP, MIBs and OIDs work?

SNMP Custom Advanced Sensor Created by SNMP Library

SNMP Custom Advanced Sensor Created by SNMP Library

Click here to enlarge.

Remarks

Add Sensor

Manually add a new sensor to an SNMP device. From the Add Sensor dialog, select SNMP Library sensor. PRTG will show a list of oidlib files available on the system. This contains all library files stored at the \snmplibs folder of your PRTG server installation directory—both the ones delivered with PRTG and your own files.

List of SNMP Library Files

List of SNMP Library Files

The filenames on the list indicate the likely purpose. Select a name that appears appropriate 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.

icon-i-blueIf the file does not fit to your device, this will result 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 adding the sensor with another file.

The SNMP Library sensor takes a list of OIDs that you imported from an MIB file into an oidlib and tests the OIDs against a device to find the OIDs the device supports. This discovery process is the meta-scan.

icon-ok-greenIf counters were found for your device, the sensor settings will open with a list of available monitoring items for you to select from. 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 Single Values: Sorted by MIB, Category, Name

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

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

The list of SNMP table values presents row values sequentially and makes it easier for you to select 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, enclose the search string in quotes.

icon-ok-greenSelect the desired counters and click Save. PRTG will now create sensors based on the OID types of the selected entries.

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

icon-i-roundOnce a custom SNMP sensor is 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. Please be aware that not all devices and/or parameters may be supported by the libraries.

  • 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, etc.
  • 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, etc.
  • 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, etc.
  • 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, BMC, chassis, COO, cooling, event log, firmware, IDE, keyboard, memory, port, network, processor, SCSI, system, temperature, USB, UUID, etc.
  • 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.
    icon-i-roundThis file may detect a very large number of interfaces. It may 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.
    icon-i-roundThis file may detect a very large number of interfaces. It may 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.
    icon-i-roundThis file may detect a very large number of interfaces. It may 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.
    icon-i-roundThis file may detect a very large number of interfaces. It may 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 tool Paessler MIB Importer. Simply convert your mib files and save the resulting oidlib files to the \snmplibs subfolder of your PRTG program directory.

icon-book-arrowsFor details about directory paths, see section Data Storage.

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

icon-toolsIf 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. PRTG will then create a lookup definition file using the lookupname of the chosen library as id parameter.

Important: The lookups will be added without state definitions, so the sensor will show a Warning status by default! You have to edit the corresponding lookup files to get reliable alarms. Please override the lookup definition with your own custom lookup as described in section Define Lookups—Customizing Lookups.

icon-prtg-on-demandPRTG in the cloud does not support the import of MIB files. You can use the SNMP Library sensor only with the default oidlib files in PRTG in the cloud.  

SNMP Library Sensor—Add Sensor Settings

The following settings for this sensor differ in the Add Sensor dialog in comparison to the sensor's settings page.

SNMP Library Specific

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 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.

Choose one or more items by adding a check mark in front of the respective line. You can also select and deselect all items by using the check box in the table head. Use the search box to narrow down to your desired items.

Depending on the kind of the chosen entries, PRTG will create the following sensor types:

Sensor Settings

On the details page of a sensor, click the Settings tab to change its settings.

icon-i-roundUsually, a sensor connects to the IP Address or DNS Name of the parent device where you created this sensor. See the Device Settings for details. For some sensor types, you can define the monitoring target explicitly in the sensor settings. Please see below for details on available settings.

Basic Sensor Settings

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, separated by spaces or commas. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

You can add additional tags to the sensor if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

Priority

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

Sensor Specific

icon-book-arrowsThe available sensor settings depend on the sensor type that the SNMP Library sensor has created. For details about settings, see the manual sections of these sensor types:

Sensor Display

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 will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor.

icon-i-roundYou can set another primary channel later by clicking the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

  • Show channels independently (default): Show an own 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 will generate an easy-to-read graph that visualizes the different components of your total traffic.
    icon-i-roundThis option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channels Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be 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 following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Root group's settings, see section Inheritance of Settings for more information. To change a setting only for this object, disable inheritance by clicking the button next to inherit from under the corresponding setting name. You will then see the options described below.

Scanning Interval

Click inherited_settings_button to disrupt the inheritance. See section Inheritance of Settings for more information.

Scanning Interval

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time 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 a sensor has time reach and check a device again in case a sensor query fails. The sensor can try to re-reach and check a device several times, depending on the option you select here, before it will be set to a Down status. This helps you avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose between:

  • Set sensor to "down" immediately: The sensor will show an error immediately after the first failed request.
  • Set sensor to "warning" for 1 interval, then set to "down" (recommended): After the first failed request, the sensor will show a yellow warning status. If the following request also fails, the sensor will show an error.
  • Set sensor to "warning" for 2 intervals, then set to "down": Show an error status only after three continuously failed requests.
  • Set sensor to "warning" for 3 intervals, then set to "down": Show an error status only after four continuously failed requests.
  • Set sensor to "warning" for 4 intervals, then set to "down": Show an error status only after five continuously failed requests.
  • Set sensor to "warning" for 5 intervals, then set to "down": Show an error status only after six continuously failed requests.

icon-i-roundSensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor to "down" immediately, so the first option will not apply to these sensor types. All other options can apply.

icon-i-roundIf a sensor has defined error limits for channels, it will always show a Down status immediately, so no "wait" option will apply.
 

icon-i-roundIf a channel uses lookup values, it will always show a Down status immediately, so no "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

icon-i-roundInheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

icon-i-roundSchedules are generally inherited. New schedules will be added to existing ones, 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" period, this object and all child objects will not be monitored. They will be in a paused state instead. Choose between:

  • Not set (monitor continuously): No maintenance window will be set and monitoring will always be 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 a currently running maintenance window.

icon-i-roundTo terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends field to a date in the past.

Maintenance Begins

This field is only visible if you enabled the 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 enabled the 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. Dependencies can be used to pause monitoring for an object depending on the status of another. You can choose between:

  • Use parent: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency.
  • Select object: Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in Down status, or is paused by another dependency. Select below.
  • Master object for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of the device, where it is created on: If the sensor is in Down status, the device will be 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 will be paused if the parent group of its parent device is in Down status, or if it is paused by another dependency.

icon-i-roundTesting your dependencies is easy! Simply choose Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if the Select object option is enabled above. Click on the reading-glasses and use the object selector to choose an object on which the current sensor will depend.

Dependency Delay (Sec.)

Define a time span in seconds for a dependency delay. After the master object for this dependency goes back to Up status, PRTG will start monitoring the depending objects after this extra delayed. This can help to avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

icon-i-round-redThis setting is not available if you choose this sensor to Use parent or to be the Master object for parent. In this case, please define delays in the parent Device Settings or in the superior Group Settings.

Access Rights

Click inherited_settings_button to disrupt the inheritance. See section Inheritance of Settings for more information.

User Group Access

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown: It contains all user groups from your setup. For each user group you can choose from the following access rights:

  • Inherited: Use the access rights settings of the parent object.
  • None: Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.
  • Read: Users in this group can see the object and review its monitoring results.
  • Write: Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.
  • Full: Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

icon-book-arrowsFor more details on access rights, see the section User Access Rights.

More

Knowledge Base: How do SNMP, MIBs and OIDs work?

Knowledge Base: How can I import my MIB files into PRTG?

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

Knowledge Base: How can I monitor EMC Isilon storage systems with PRTG?

Knowledge Base: My SNMP sensors don't work. What can I do?

Edit Sensor Channels

To change display settings, spike filter, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, see the Sensor Channels Settings section.

Notifications

Click the Notifications tab to change notification triggers. For detailed information, see the Sensor Notifications Settings section.

Others

For more general information about settings, see the Object Settings section.

Sensor Settings Overview

For information about sensor settings, see the following sections: