Device and Sensor Setup > Sensor Settings

PRTG Manual: SNMP Trap Receiver Sensor

The SNMP Trap Receiver sensor receives and analyzes Simple Network Management Protocol (SNMP) traps.

The sensor can also show the actual trap messages.

For a detailed list and descriptions of the channels that this sensor can show, see section Channel List.

SNMP Trap Receiver Sensor

Sensor in Other Languages

Dutch: SNMP Trap Receiver
French: Récepteur de traps SNMP
German: SNMP-Trap-Empfänger
Japanese: SNMP トラップレシーバー
Portuguese: Receptor de trap SNMP
Russian: Приемник ловушек SNMP
Simplified Chinese: SNMP 陷阱接收程序
Spanish: Receptor SNMP Trap

Remarks

This sensor can have a high impact on the performance of your monitoring system. Use it with care. We recommend that you use no more than 50 sensors of this sensor type on each probe.
This sensor does not support SNMP v3 traps. Use SNMP v1 or v2c instead.
This sensor only supports the User Datagram Protocol (UDP).
Add this sensor to the probe device to receive all messages of the remote probe system.
Add this sensor to a specific device to directly receive all messages from this device. This makes this sensor faster than when you use source filters.
This sensor supports the IPv6 protocol.

This sensor has a very high performance impact.

You can use specific placeholders in email notification templates to see the messages when you receive an email notification. See section List of Placeholders for Notifications.
The sensor states of this sensor persist for one scanning interval only. After showing a Warning status or a Down status, and if there is no warning or error message in the following scanning interval, the sensor shows an Up status again. For a workaround, see the Knowledge Base: How can I configure sensors using speed limits to keep the status for more than one interval?
With the available filter options, you can individually define which types of messages the sensor considers for monitoring, and which messages it categorizes as warning or error messages. Depending on the filters, received messages are counted in the respective channels.
If you do not add the sensor to a probe device but to a different device in PRTG, be careful with the configuration: Ensure that the IP address or Domain Name System (DNS) name of the parent device matches the proper sender. For example, if you want to receive messages from a storage area network (SAN), you might have to add a device to PRTG using the IP address of a specific array member that sends the messages. Providing a DNS name that points to the IP address of a whole group might not work for SANs.
In PRTG on premises, you can copy the Management Information Base (MIB) file for your traps into the \MIB subfolder of the PRTG program directory to translate the object identifiers (OID) for the traps into readable messages. For details, see the Knowledge Base: How can I show the name of a received OID in PRTG?
You cannot use this sensor in cluster mode. You can only set it up on a local probe or a remote probe but not on a cluster probe.
See the Knowledge Base: How do I test an SNMP Trap Receiver Sensor?
For a general introduction to the receiver's configuration, see section Monitoring Syslogs and SNMP Traps.

You cannot add this sensor to the hosted probe of a PRTG hosted by Paessler instance. If you want to use this sensor, add it to a remote probe device.

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

Add Sensor

The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

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. 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 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: snmptrapsensor
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 ().

SNMP Trap Specific

Setting	Description
Listen on Port	Enter the number of the port on which the sensor listens for SNMP traps. The default port is 162. Enter an integer value. We recommend that you use the default value.
Purge Messages After	Define for how long PRTG stores received trap messages for analysis. Choose a period of time from the dropdown list.

Filter

For detailed information, see section Filter Rules.

Setting	Description
Include Filter	Define if you want to filter traps. If you leave this field empty or use the keyword "any", the sensor processes all data. This setting is default. To include only specific types of traps, define filters using a special syntax.
Exclude Filter	Define which types of traps the sensor discards and does not process. To exclude specific types of traps, define filters using a special syntax.
Warning Filter	Define which types of traps count for the Warnings channel. To categorize received traps as warning messages, define filters using a special syntax. Messages are collected until a scanning interval ends. As long as the scanning interval is running, no status change happens. By default, the sensor changes to the Warning status after a scanning interval has finished and there has at least been one warning message (and no error message) during this interval. The sensor shows the Warning status at least until the succeeding scanning interval has finished. If the sensor does not receive any warning or error message in this scanning interval, its status changes to the Up status again with the start of the next scanning interval.
Error Filter	Define which types of traps count for the Errors channel. To categorize received traps as error messages, define filters using a special syntax. Messages are collected until a scanning interval ends. As long as the scanning interval is running, no status change happens. By default, the sensor changes to the Down status after a scanning interval has finished and there has at least been one error message during this interval. The sensor shows the Down status at least until the succeeding scanning interval has finished. If the sensor does not receive any warning or error message in this scanning interval, its status changes to the Up status again with the start of the next scanning interval.

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. You should 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. 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 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 1 day 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
1 day

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.

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 a 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.

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.

Channel Unit Configuration

Click to interrupt the inheritance.

Setting	Description
Channel Unit Types	For each type of channel, select the unit in which PRTG displays the data. If you define this setting on probe, group, or device level, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available): Bandwidth Memory Disk File Custom Custom channel types are only available on sensor level.

Setting

Description

Channel Unit Types

For each type of channel, select the unit in which PRTG displays the data. If you define this setting on probe, group, or device level, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available):

Bandwidth
Memory
Disk
File
Custom

Custom channel types are only available on sensor level.

Debug Options

Setting	Description
Result Handling	Define what PRTG does with the sensor result: Discard result (recommended): Do not store the sensor result. Store result: Store the last sensor result in the \Logs\debug subfolder of the PRTG data directory on the probe system. This setting is for debugging purposes. Use with caution. We recommend that you only use this setting for a short time because it can create huge data files.

Setting

Description

Result Handling

Define what PRTG does with the sensor result:

Discard result (recommended): Do not store the sensor result.

Store result: Store the last sensor result in the \Logs\debug subfolder of the PRTG data directory on the probe system. This setting is for debugging purposes.
Use with caution. We recommend that you only use this setting for a short time because it can create huge data files.

Filter Rules for Traps

Filter rules are used for the include, exclude, warning, and error definition fields of the SNMP Trap Receiver sensor. They are based on the following format:

field[filter]

You can use various filters that are suitable to your needs. Include and exclude filters to define which traps to monitor. Warning and error filters define how to categorize received traps. Provide these filters in the sensor settings as formulas. Formulas are fields that you can combine with boolean operators (AND, OR, NOT) and brackets.

Field	Parameter	Examples
source[ip]	Enter an IP address where the UDPs come from. IP masks and ranges are also possible.	source[10.0.23.50], source[10.0.23.10-50], source[10.0.23.10/24]
agent[ip]	Enter an IP address that specifies the object that creates the SNMP trap. Only v1 is supported.	agent[10.0.0.1]
enterprise[oid]	Enter an OID that specifies the object that originates the trap. Only v1 is supported.	enterprise[1.3.6.1.4.1.2.6.182.1.2.31.1.0]
bindings[text]	Enter a substring to match all OIDs and values in the bindings.	bindings[ERROR], bindings[1.3.6.1.4.1.2.6.182.1.2.31.1.0], bindings["port blocked"] It is not necessary to use quotation marks (") to find strings. If the string contains quotation marks that you want to include in the filter, you need to escape them with quotation marks.
bindings[oid,value]	Enter an OID and a substring to match a value in the specified OID. Separate OID and value with a comma.	bindings[1.3.6.1.4.1.2.6.182.1.2.31.1.0,error]
bindings[oid,value,mode]	Enter an OID, a substring, and a mode to match a value in the specified OID. Separate the OID, the value, and the mode with a comma. The mode can be: substring: This is the default mode that works like bindings[oid,value]. exact: This mode enforces an exact match of a value. equal, greater, greaterorequal, less, or lessorequal: This interprets and compares values as numbers. It only supports integer values without extra characters and without thousands separators. Hex format is also supported.	bindings[1.3.6.1.4.1.2.6.182.1.2.31.1.0,error,exact] bindings[1.3.6.1.4.1.2.6.182.1.2.31.1.0,10,equal]
gentrap[number]	Enter a number that specifies the generic trap type. Ranges are also possible.	gentrap[3], gentrap[2-6]
spectrap[number]	Enter a number that defines the specific trap code. Ranges are also possible.	spectrap[4], spectrap[0-3]
version[number]	Enter a number (1 or 2) that specifies the SNMP version.	version[1], version[2]
community[text]	Enter a community string for an exact, case-sensitive match.	community[public], community[private]

Messages Tab: Review and Analyze Traps

PRTG stores received traps as common files in the \Trap Database subfolder of the PRTG data directory. To review and analyze all received messages, you can directly access the most recent data in a table list on the PRTG web interface. You can access this list via the sensor's Overview tab.

Received traps are only shown in the table on the Overview tab after an (automatic) page refresh following a sensor scan. The default value for auto refresh is 30 seconds.

For more details and further filter options, click the Messages tab of the SNMP Trap Receiver sensor. You see all received messages in a table list. On the top, you have display filter options to drill down into the data for specific events of your interest. The filters are the same as those available in the sensor settings, but you can define them without using formulas. Provide the desired parameters and PRTG automatically loads the filtered list.

Boolean operators are automatically applied to the filters in the following manner: parameters across all columns are combined with AND, and parameters within a single column are combined with OR.

The parameters entered into the filters have to exactly match the parameters in the message. They are case sensitive.

You can automatically add a filter by clicking the content of a column.

Advanced Filter Settings

You can open advanced filter settings by clicking in the Filter row. The Advanced Filter appears in a popup window. In the text field, you can define a filter using the syntax as described in section Filter Rules for Traps.

If you provided filter parameters on the Messages tab, the advanced filter already includes them as a corresponding formula with the correct syntax. You can adjust this filter to your needs. You can also copy the automatically created and manually adjusted formula for usage in the filter fields of the sensor settings.

Channel List

Which channels the sensor actually shows might depend on the monitored device, the available components, and the sensor setup.

Channel	Description
Downtime	In the channel table on the Overview tab, this channel never shows any values. PRTG uses this channel in graphs and reports to show the amount of time in which the sensor was in the Down status in percent.
Drops	The number of dropped packets per second on the SNMP trap collector port
Errors	The number of messages categorized as "error" per second
Messages	The overall number of received traps per second This channel is the primary channel by default.
Warnings	The number of messages categorized as "warning" per second