PRTG 9 Manual: Glossary

This section explains special words used in the context of PRTG Network Monitor. Note: Here, only explanations are given. For information on where to find detailed instructions for a specific key word, please see the Index section. It is only available in the PDF version of this manual.


The monitoring data of a sensor is shown in sensor channels. For example, for sensors that measure network traffic, there is one channel each for traffic in and traffic out. You can set various triggers for each channel, enabling you to set sensor status changes or notifications based on the monitoring data received.


PRTG can be configured as a failover cluster for fail-safe monitoring. In a cluster, one or more core servers work together in one configuration. Every node can monitor all devices in a network for gapless monitoring, additionally enabling you to compare monitoring results measured from different perspectives.

Cluster Node

Sometimes used as synonym for Node.

Cluster Probe

When running PRTG in cluster mode, a cluster probe is automatically created. All objects created on the cluster probe, or below it in the device tree, are monitored by all nodes in the cluster. Create or move objects there to monitor them fail-safely. If one node fails, the other nodes will continue to monitor them. You can add groups and devices to the probe. On a PRTG installation, the cluster probe runs as part of this installation's local probe. Remote probes cannot be connected to a cluster probe, but only to one local probe of one PRTG installation.

Core Server

The central unit of PRTG. It receives monitoring data from the probe(s) and handles reporting and notifications, provides the web server for the user interfaces, and many other things. In a cluster, one core server is installed on every node.


In the Home menu of the web interface there are several pre-configured dashboards available which show a quick overview of the overall status of your monitoring configuration. Custom dashboards can be created using the Maps function.


A device in PRTG represents a physical device in the network. For an easily understandable tree structure, you usually create one PRTG device for each physical device you want to monitor (exceptions apply to some sensors that can only be created on the local probe device, and for sensor types that are not bound to a certain device, such as HTTP sensors, which are also usually created on the local probe). You can add one or more sensors on every device.

Device Tree

PRTG's configuration is represented in a hierarchical tree structure, called device tree, containing all objects. While building the tree, you can relate to your network's topology to make your monitoring setup easy to understand.

Failover Master (Node)

If the primary master node fails, a failover node is promoted to current failover master and takes over the master role until the primary master node re-joins the cluster.

Failover Node

In a cluster a failover node monitors all sensors on the cluster probe, providing monitoring data for the core server. Additionally, it serves as a backup in case the master node fails.


A group is an organizational unit in your PRTG tree structure that helps to arrange your devices. To existing groups, you can add devices, or additional sub-groups. This way you can model your physical network's topology within the PRTG configuration.


Libraries are a way to show parts of your device tree in a different layout or with different filters enabled. There is an editor available that allows creating libraries directly in your browser.

Local Probe

The local probe is installed together with the core server. All objects created on the local probe, or below it in the device tree, are monitored by the local core system. You can add groups and devices to the probe.


Maps (sometimes referred to as "dashboard") are a way to present monitoring the way you want to arrange it. There is an editor available that allows creating maps directly in your browser.

Master Node

In a cluster, the master node controls the settings and cluster management. It also takes over notifications. All changes to the monitoring configuration are made on the master node.


In a cluster there is one master node and one or more failover nodes. On each node, one PRTG core server installation is running independently. All nodes are connected to each other, exchanging configuration and monitoring data.


All different items in the device tree are generally referred to as objects. An object can be a probe, a group, a device, or a sensor.

Primary Master (Node)

The primary master node in a cluster is the node that is master by configuration. Only if it fails, one of the failover nodes becomes failover master and takes over the master role until the primary master node re-joins the cluster.


On a probe, the actual monitoring takes place. A probe can run as local probe on the local system where the core server is installed. There are also cluster probes and remote probes.

Remote Probe

A remote probe is a small piece of software installed on a computer in the local or remote network. It scans the network from there and sends monitoring results to the core server. Once the connection is established, the remote probe is shown in the PRTG tree structure. All objects created on the remote probe, or below it in the device tree, are monitored by the remote system running the remote probe. You can add groups and devices to the probe. In cluster, remote probes can only be connected to the master node, not to one of the failover nodes.


A sensor monitors one aspect of a device. For example, monitoring if a device responds to a Ping request is done by one sensor. Monitoring the traffic of one ethernet port of a router device is done by another sensor. For monitoring the CPU load of the local system yet another sensor is set up, and so on. A sensor's data is shown in channels.

Sensor Tree

Sometimes used as synonym for device tree.


ToDos are created by the system and contain important messages or action steps to take for the administrator. Every ToDo should be acknowledged. You can access the list of ToDos from the main menu.


Paessler designates all kinds of flow protocols as xFlow. Currently, PRTG supports NetFlow V5 and V9, sFlow V5, and jFlow V5.



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