PRTG Manual: SNMP Cisco ASA VPN Users 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.

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).

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 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.

SNMP Version

Select the SNMP version for the device connection. Choose between:

• v1 : Use the simple v1 protocol for SNMP connections. This protocol only offers clear-text data transmission, but it is usually supported by all devices.
  SNMP v1 does not support 64-bit counters which may result in invalid data when monitoring traffic via SNMP.
   
• v2c (recommended) : Use the more advanced v2c protocol for SNMP connections. This is the most common SNMP version. Data is still transferred as clear-text, but it supports 64-bit counters.
• v3 : Use the v3 protocol for SNMP connections. It provides secure authentication and data encryption.

When using SNMP v3 you can only monitor a limited number of sensors per second due to internal limitations. The limit is somewhere between 1 and 50 sensors per second (depending on the SNMP latency of your network). This means that using an interval of 60 seconds limits you to between 60 and 3000 SNMP v3 sensors for each probe. If you experience an increased Interval Delay or Open Requests with the Probe Health Sensor , distribute the load over multiple probes. SNMP v1 and v2 do not have this limitation.

Community String

This setting is only visible if you select SNMP version v1 or v2c above. Enter the community string of your devices. This is a kind of "clear-text password" for simple authentication. We recommend that you use the default value.

Authentication Type

This setting is only visible if you select SNMP version v3 above. Choose between:

• MD5 : Use Message-Digest Algorithm 5 (MD5) for authentication.
• SHA : Use Secure Hash Algorithm (SHA) for authentication.

The type you choose must match the authentication type of your device.

If you do not want to use authentication, but you need SNMP v3, for example, because your device requires context, you can leave the field Password empty. In this case, SNMP_SEC_LEVEL_NOAUTH is used and authentication deactivated entirely.

User

This setting is only visible if you select SNMP version v3 above. Enter a username for secure authentication. This value must match the username of your device.

Password

This setting is only visible if you select SNMP version v3 above. Enter a password for secure authentication. This value must match the password of your device.

Encryption Type

This setting is only visible if you select SNMP version v3 above. Select an encryption type. Choose between:

• DES : Use Data Encryption Standard (DES) as encryption algorithm.
• AES : Use Advanced Encryption Standard (AES) as encryption algorithm.

AES 192 and AES 256 are not supported by Net-SNMP because they lack RFC specification.
 

The type that you choose must match the encryption type of your device.

Data Encryption Key

This setting is only visible if you select SNMP version v3 above. Enter an encryption key here. If you provide a key in this field, SNMP data packets are encrypted using the encryption algorithm selected above, which provides increased security. The key that you enter here must match the encryption key of your device.

If the key you enter in this field does not match the key configured on the target SNMP device, you will not get an error message about this! Please enter a string or leave the field empty.

Context Name

This setting is only visible if you select SNMP version v3 above. Enter a context name only if it is required by the configuration of the device. Context is a collection of management information accessible by an SNMP device. Please enter a string.

SNMP Port

Enter the port for the SNMP communication. We recommend that you use the default value.

SNMP Timeout (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than the value you enter here, the request is aborted and an error message triggered.

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.

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" 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.

To 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.

Testing 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.

This 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 .

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, please see the section User Access Rights .