<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: DHCP Sensor

DHCP Specific

Specify Network Interface

Select the network adapters you want to add a sensor for. You see a list with the names of all items which are available to monitor. Select the desired items by adding check marks in front of the respective lines. PRTG creates one sensor for each selection. You can also select and deselect all items by using the check box in the table head.

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 space or comma. 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 it, 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).

MAC

Shows the MAC address of the network adapter that is used to send the broadcast message to the network. Once a sensor is created, you cannot change this value. It is shown for reference purposes only. If you need to change this, please add the sensor anew.

Client IP

Specify if you want to check the returned client IP with a regular expression. Choose between:

• Don't check: The IP will only appear in the sensor message without further processes.
• Check: Enter the regular expression you want to use below.

Client IP Must Include

This field is only visible if you chose to check the client IP above. In the response of the DHCP server, search using a regular expression. If the answer for the client IP does not contain the defined string, the sensor shows a Down status.

For example, enter 10\.0\.5\..* to make sure any answering DHCP server returns an client IP address starting with "10.0.5.". If it does not, the sensor will show an error. For more details, see Regular Expressions section. Leave empty to not use this field.

Client IP Must Not Include

This field is only visible if you choose to check the client IP above. In the response of the DHCP server, search using a regular expression. If the answer for the client IP contains the defined string, the sensor shows a Down status.

See example above. For more details, see Regular Expressions section. Leave empty to not use this field.

Server IP

Specify if you want to check the returned server IP with a regular expression. Choose between:

• Don't check: The IP only appears in the sensor message without further processes.
• Check: Enter the regular expression you want to use below.

Server IP Must Include

This field is only visible if you choose to check the server IP above. In the response of the DHCP server, search using a regular expression. If the answer for the server IP does not contain the defined string, the sensor shows a Down status.

See example above. For more details, see Regular Expressions section. Leave empty to not use this field.

Server IP Must Not Include

This field is only visible if you choose to check the server IP above. In the response of the DHCP server, search using a regular expression. If the answer for the server IP contains the defined string, the sensor shows a Down status.

See example above. For more details, see Regular Expressions section. Leave empty to not use this field.

Timeout (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value defines, the sensor will cancel the request and show a corresponding error message. Please enter an integer value. The maximum value is 900 seconds (15 minutes).

DHCP Server Change

If there is more than one DHCP server in the network that may answer to the broadcast message, the sensor can receive an answer from a different DHCP server, compared to the last scan of the sensor. In this case, PRTG can write an entry to the system Logs. Choose between:

• Ignore: Do not write a log entry if the DHCP server changes.
• Write log entry: Write an entry to the system Logs whenever the DHCP server changes between two sensor scans.

Note: Regardless of this setting, those entries will always be added to the sensor Log.

Offered IP Change

If the IP address offered by the DHCP server changes between two sensor scans, PRTG can write an entry to the system Logs. Choose between:

• Ignore: Do not write a log entry if the offered IP address changes.
• Write log entry: Write an entry to the system Logs whenever the DHCP server offers a different IP address compared to the last sensor scan.

Note: Regardless of this setting, those entries will always be added to the sensor Log.

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. Note: You can set another primary channel later by clicking on the pin symbol of a channel in the sensor's Overview tab.

Chart 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 which visualizes the different components of your total traffic. Note: 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.

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.

When a Sensor Reports an Error

Define the number of scanning intervals that a sensor has time to report an error before the sensor will be set to a Down status. The sensor can try to reach a device several times, depending on the setup you can specify here, to help 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.

Note: 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 "down" immediately, so the first option will not apply to these sensor types (all other options can apply).

Note: If a sensor has defined error limits for channels, this sensor will always be set to a Down status immediately, so no "wait" option will apply.

Note: If a channel uses lookup values, the sensor will always be set to a Down status immediately, so no "wait" options will apply.

Note: 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) throughout the 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.

Note: 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.

Note: To terminate a current maintenance window before the defined end date, you can change the time in Maintenance End At field to a date in the past.

Maintenance Begins At

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 End At

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 a Down status, or if the sensor is paused by another dependency.
• Select object: Pause the current sensor if the device, where it is created on, is in an Down status, or if the sensor is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in a Down status, or if it 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 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 of its parent device is in a Down status, or if it is paused by another dependency.

Note: 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.

Delay (Seconds)

Define a time span. After the master object for this dependency comes back to an Up status, the beginning of the monitoring of the depending objects will be additionally delayed by the time span you define here. 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 in seconds. Note: This setting is not available if you choose this sensor 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.