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.

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:

• snmpcustomstringsensor

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 ().

OID

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

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

Maximum Length of String

Define the maximum length of the string that PRTG receives from the SNMP object at the OID. If the string is longer than this value, the sensor shows the Down status. Enter an integer value or leave the field empty.

If Value Changes

Define what the sensor does when the sensor value changes:

• Ignore changes (default): Take no action on change.
• Trigger 'change' notification: Send an internal message indicating that the sensor 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 if Not Included)

Define the search string that must be part of the data that PRTG receives from the SNMP object at the OID. You can enter a simple string in plain text or a regular expression (regex).

The search string must be case sensitive.

If the data does not include the search pattern, the sensor shows the Down status.

Search Method

Define the method with which you want to provide the search string.

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Response Must Not Include (Down Status if Included)

Define the search string that must not be part of the data that PRTG receives form the SNMP object at the OID. You can enter a simple string in plain text or a regex.

The search string must be case sensitive.

If the data does include the search pattern, the sensor shows the Down status.

Search Method

Define the method with which you want to provide the search string.

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Response Must Include (Warning Status If Not Included)

Define the search string that must be part of the data that PRTG receives from the SNMP object at the OID. You can enter a simple string in plain text or a regex.

The search string must be case sensitive.

If the data does not include the search pattern, the sensor shows the Warning status.

Search Method

Define the method with which you want to provide the search string.

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Response Must Not Include (Warning Status If Included)

Define the search string that must not be part of the data that PRTG receives form the SNMP object at the OID. You can enter a simple string in plain text or a regex.

The search string must be case sensitive.

If the data does include the search pattern, the sensor shows the Warning status.

Search Method

Define the method with which you want to provide the search string.

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character. You cannot change this behavior. The literal search for these characters is only possible with a regex.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Interpret Result As

Define the type of the received string:

• String (default): Handle the result as a common string.
• Bytes in hexadecimal notation: Handle the result as bytes in hexadecimal notation. For example, select this option if you monitor MAC addresses.
• Bytes in decimal notation: Handle the result as bytes in decimal notation. For example, select this option if you monitor IP addresses.

Numeric Value Extraction

Define if you want to filter out a numeric value from the received string:

• Do not use extraction: Do not extract a float value. Use the result as a string value.
• Use a regular expression for extraction: Use a regular expression (regex) to identify a numeric value in the string and to convert it to a float value to use it, for example, with channel limits. Define below. See also the example.
  For more information, see section Channel Settings.

Regular Expression

This setting is only visible if you select Use a regular expression for extraction above. Enter a regular expression to identify the numeric value that you want to extract from the string returned by the SNMP object at the specified OID. You can use capturing groups.

Make sure that the expression only returns numbers, including the decimal and thousands separators.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. For more details, see section Regular Expressions.

Index of Capturing Group

This setting is only visible if you select Use a regular expression for extraction above. If your regex uses capturing groups, specify which one captures the number. Enter an integer value or leave the field empty.

Decimal Separator

This setting is only visible if you select Use a regular expression for extraction above. Define the character for the decimal separator of the number. Enter a string or leave the field empty.

Thousands Separator

This setting is only visible if you select Use a regular expression for extraction above. Define the character for the thousands separator of the number. 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 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.

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.

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.

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.

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.

Extracted Value

The value extracted from the string (optional)

Response Time

The response time in milliseconds (msec)

This channel is the primary channel by default.