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PRTG Manual: Auto-Discovery

The auto-discovery searches for devices in your network and automatically updates the device tree with devices and recommended sensors. The auto-discovery is primarily intended for devices that are in the same network as your probes.

Unless you skip the auto-discovery during the installation process, PRTG runs an initial auto-discovery as soon as you finish the installation of PRTG. It automatically creates devices that are available in your network that are reachable via ping. For each device, the auto-discovery also creates recommended sensors based on device templates.

Auto-discovery is available on multiple levels:

The original auto-discovery that PRTG runs upon installation.
Auto-discovery on existing groups and devices to detect new devices in a group or to add newly available sensors to a device.
Auto-discovery groups to use the auto-discovery for a range of IP addresses or for individual devices.
Auto-discovery tasks to run customized auto-discoveries on a probe, group, or device in the modern PRTG user interface.

You can run an auto-discovery one time, on demand via the context menu, or via a schedule. If you run the auto-discovery at group level daily or weekly, it automatically creates new devices when they connect to the network and adds suitable sensors.

PRTG creates a notification ticket when it finds one or more new devices or sensors via auto-discovery. You also receive a ticket if an error occurs. By default, PRTG sends tickets via email. You can change this in the My Account settings.

HTTP sensors' names indicate the protocol that they use to access the target device (HTTP, HTTP (8080), and HTTPS). This distinguishes HTTP sensors from each other if the auto-discovery adds more than one HTTP sensor to a device.

How Auto-Discovery Works

The auto-discovery has three steps:

Scan a network segment for devices via ping (at the group level only).
Assess the device type for all of the devices that it discovered in step 1 (via the Simple Network Management Protocol (SNMP), Windows Management Instrumentation (WMI), and other protocols).
Create sensor sets that match the discovered device type. The auto-discovery does this based on built-in device templates that have recommended sensors for many device types. Optionally, it can also create sensor sets via custom device templates.

Restrictions

Note the following restrictions of the auto-discovery:

PRTG cannot discover devices that are not reachable via ping. This is because step 1 scans for devices via ping. If, for example, a firewall blocks echo requests, PRTG cannot discover a device behind the firewall.
If a device has more than one IP address, it might show up more than once in the auto-discovery results, even though PRTG tries to identify these situations.
Auto-discovery on the group level does not create new sensors on devices that already exist. If you want to automatically add sensors to a device, run the auto-discovery on the device via its context menu.
Frequent auto-discoveries of large network segments can lead to performance issues. Because of this we recommend that you only schedule regular auto-discoveries where necessary.
For more information, see the Knowledge Base: Why can automatic auto-discoveries evoke performance issues?
PRTG automatically adds suitable device icons to discovered devices. PRTG uses a device's MAC address for this purpose, which it determines via the Address Resolution Protocol (ARP). This only works via IPv4 and not via IPv6. Usually, ARP only works within the local network. If you want PRTG to identify devices on a different subnet, your router must support proxy ARP and be configured accordingly.
The auto-discovery does not apply the user group setting Allowed Sensors. Therefore, the auto-discovery adds all sensors that are defined in the used device templates.

Auto-discovery for groups is not available on hosted probes.

Run an Auto-Discovery

You can run an auto-discovery at any time on a specific device. To do so, right-click the device and select Auto-Discovery | Run Auto-Discovery from the context menu. PRTG immediately starts to search for new sensors to add to the device. If you use the auto-discovery for an auto-discovery group, PRTG adds devices with suitable sensors, if it finds any. In the corresponding page header bar, you can always see when PRTG ran the last auto-discovery on a selected group or device.

The auto-discovery also adds manually deleted devices or sensors again. If you do not want this to happen, you must always create objects manually.

Auto-Discovery in Progress

While the auto-discovery is in progress, you might experience a lower system performance than usual because PRTG is working in the background to discover your network. Depending on the IP address ranges defined (up to 65,536 addresses), the discovery might run for up to several days before it is complete. You can review the status of the discovery process as follows:

In the device tree, next to the group or device name. You can see a percentage value that shows the progress of the auto-discovery.
In a pop-up box in the bottom-right corner of the PRTG web interface. You can see the number of active auto-discovery tasks.
In the modern PRTG UI, on the auto-discovery overview page. You can see all running auto-discovery tasks.

To stop an auto-discovery, right-click the group or device in the device tree where the auto-discovery is running and select Pause | For 5 Minutes from the context menu. PRTG pauses monitoring for the object and cancels the auto-discovery task. When PRTG resumes monitoring, the auto-discovery does not resume.

Disable Auto-Discovery

You can disable the initial auto-discovery for a fresh PRTG installation in two ways:

Run the installer and select the Custom installation mode. When prompted, select Skip auto-discovery.
Run the installer in a command prompt and add /NoInitialAutoDisco=1 as a parameter.

This might be useful for performance reasons or if you prefer to manually add devices and sensors to your installation.

To disable auto-discovery for a group or device, go to the object settings and select No auto-discovery (default) under Auto-Discovery Settings | Auto-Discovery Level.

You can use multi-edit to disable auto-discovery for multiple devices at once:

1. From the main menu in the PRTG web interface, navigate to Devices | Device List.
2. Select the devices that you want to edit and click the settings symbol ().
3. Enable the checkbox next to Auto-Discovery Level and select No auto-discovery (default).
4. Click OK to apply your changes.