PRTG Manual: SNMP Custom String Sensor

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.

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

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.

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

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).

OID Value

Enter the OID of the SNMP object you want to receive a string from.

Most OIDs begin with 1.3.6.1. However, entering OIDs starting with 1.0, or 1.1, or 1.2 is also allowed. If you want to disable the validation of your entry entirely, add the string norfccheck: at the beginning of your OID, for example, norfccheck:2.0.0.0.1.

Maximum Length of String

Define the maximum allowed length of the string to be received from the SNMP object at the given OID. If the string is longer than this value, the sensor shows a Down status. Please enter an integer value or leave the field empty.

If Value Changes

Define what this sensor will do when the sensor value changes. You can choose between:

• Ignore changes (default): The sensor takes no action on change.
• Trigger 'change' notification: The sensor sends an internal message indicating that its value has changed. In combination with a Change Trigger, you can use this mechanism to trigger a notification whenever the sensor value changes.

Response Must Include (Down Status)

Define which string must be part of the data that is received from the SNMP object at the given OID. You can either enter plain text or a Regular Expression. If the data does not include the search pattern, the sensor shows a Down status. Please enter a string or leave the field empty.

For Keyword Search Use

Define in which format you have entered the search expression in the field above.

• Plain Text: Search for the string as plain text. The characters asterisk * and question mark ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). You cannot disable this behavior, so the literal search for these characters is not possible with plain text search.
• Regular Expression: Use the search pattern as a Regular Expression.

PRTG supports PCRE regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Response Must Not Include (Down Status)

Define which string must not be part of the data that is received form the SNMP object at the given OID. You can either enter plain text or a Regular Expression. If the data does include the search pattern, the sensor shows a Down status. Please enter a string or leave the field empty.

For Keyword Search Use

Define in which format you have entered the search expression in the field above.

• Plain Text: Search for the string as plain text. The characters asterisk * and question mark ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). You cannot disable this behavior, so the literal search for these characters is not possible with plain text search.
• Regular Expression: Use the search pattern as a Regular Expression.

PRTG supports PCRE regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Response Must Include (Warning Status)

Define which string must be part of the data that is received from the SNMP object at the given OID. You can either enter plain text or a Regular Expression. If the data does not include the search pattern, the sensor shows a Warning status. Please enter a string or leave the field empty.

For Keyword Search Use

Define in which format you have entered the search expression in the field above.

• Plain Text: Search for the string as plain text. The characters asterisk * and question mark ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). You cannot disable this behavior, so the literal search for these characters is not possible with plain text search.
• Regular Expression: Use the search pattern as a Regular Expression.

PRTG supports PCRE regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Response Must Not Include (Warning Status)

Define which string must not be part of the data that is received form the SNMP object at the given OID. You can either enter plain text or a Regular Expression. If the data does include the search pattern, the sensor shows a Warning status. Please enter a string or leave the field empty.

For Keyword Search Use

Define in which format you have entered the search expression in the field above.

• Plain Text: Search for the string as plain text. The characters asterisk * and question mark ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). You cannot disable this behavior, so the literal search for these characters is not possible with plain text search.
• Regular Expression: Use the search pattern as a Regular Expression.

PRTG supports PCRE regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Interpret Result As

Define the type of the received string. Choose from:

• String (default): Handle the result as common string.
• Hexadecimal bytes (as in MAC addresses): Handle the result as hexadecimal bytes. For example, choose this option when monitoring MAC addresses.
• Decimal bytes (as in IP addresses): Handle the result as decimal bytes. For example, choose this option when monitoring IP addresses.

Extract Number Using Regular Expression

Define if you want to filter out a numeric value from the string received from the SNMP object at the given OID. You can convert this into a float value to use it with channel limits (see Sensor Channel Settings).

• No extraction: Do not extract a float value. Use the result as a string value.
• Extract a numeric value using a regular expression: Use a regular expression to identify a numeric value in the string and convert it to a float value. Define below. See also the example below.

Regular Expression

This setting is only visible if you enable number extraction above. Enter a Regular Expression to identify the numeric value you want to extract from the string returned by the SNMP object at the given OID. You can use capturing groups here.

Make sure the expression returns numbers only (including decimal and thousands separators). The result will be further refined by the settings below.

PRTG supports PCRE regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Index of Capturing Group

This setting is only visible if you enable number extraction above. If your regular expression uses capturing groups, specify which one will be used to capture the number. Please enter an integer value or leave the field empty.

Decimal Separator

This setting is only visible if you enable number extraction above. Define which character is used as decimal separator for the number extracted above. Please enter a string or leave the field empty.

Thousands Separator

This setting is only visible if you enable number extraction above. Define which character is used as thousands separator for the number extracted above. Please enter a string or leave the field empty.

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.

You 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.
  This option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channel 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.

Click 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 to 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 from:

• 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 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 consecutively failed requests.
• Set sensor to warning for 3 intervals, then set to down: Show an error status only after four consecutively failed requests.
• Set sensor to warning for 4 intervals, then set to down: Show an error status only after five consecutively failed requests.
• Set sensor to warning for 5 intervals, then set to down: Show an error status only after six consecutively failed requests.

Sensors 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.

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

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

Inheritance 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.

Schedules 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, the current sensor and all child objects will not be monitored. They will be in a Paused status 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.

To terminate a current 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 start 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 another object. You can choose from:

• Use parent: Use the dependency type of the parent device.
• Select a sensor: Use the dependency type of the parent device. Additionally, pause the current sensor if another specific sensor is in a Down status or in a Paused status caused by another dependency. Select below.
• Master sensor for parent: Make this sensor the master object for its parent device. The sensor will influence the behavior of its parent device: If the sensor is in a 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 is paused by another dependency.

Testing your dependencies is easy! Simply select 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 you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current sensor will depend.

Dependency Delay (Sec.)

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

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects will be additionally delayed by the defined time span. This can help 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.

This setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, please define delays in the parent Device Settings or in its parent Group Settings.

Click 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.

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