<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: Glossary

This section explains special words used in the context of PRTG Network Monitor.


The alarms list shows all sensors that are currently in a Down, Down (Partial), Down (Acknowledged), Warning, or Unusual status. The alarms list helps you to keep track of all irregularities in your network.


The auto-discovery process uses Ping to scan your network for devices (for groups only), it assesses the device type for all discovered devices, and it creates sensor sets that match the discovered device types based on built-in templates or your custom device templates.


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


A cluster consists of two or more PRTG core servers that work together to form a high availability monitoring system. A cluster consists of at least a master node and one or more failover nodes. Every node can monitor every device in a network for fail-safe monitoring, so you can additionally compare monitoring results measured from different perspectives. This feature is not available in PRTG hosted by Paessler.

Cluster Node

Cluster node is a synonym for node.

Cluster Probe

When running PRTG in cluster mode, PRTG automatically creates a cluster probe. All objects that you create on the cluster probe or below in the device tree are monitored by all nodes in the cluster. Create or move objects there for fail-safe monitoring. If one node fails, the other nodes continue to monitor all objects. You can add groups and devices to the cluster probe. On a PRTG installation, the cluster probe runs as part of this installation's local probe.


Several preconfigured dashboards are available in the Home menu of the PRTG web interface. Dashboards provide an overview of the overall status of your monitoring configuration. You can create custom dashboards using maps.


A device in PRTG represents a physical or virtual component in your network that is reachable via an IP address. For a clear tree structure, you usually create one device in PRTG for each physical or virtual component that you want to monitor. You can add one or more sensors to a device.

Device Template

If you want to add a specific device several times, you can create a device template from an existing device in your device tree. When you create a device template, PRTG saves information for nearly all sensors on this device to a template file that you can later use in combination with the auto-discovery (restrictions apply for a few sensor types).

Device Tree

The configuration of PRTG is represented in a hierarchical tree structure called the device tree, which contains all objects. While building the device tree, you can relate to your network's topology to make your monitoring setup more understandable.

Failover Master (Node)

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

Failover Node

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

Geo Maps

Geo Maps show the different locations of your devices on a map depending on the location data that you provide in the settings of probes, groups, or devices. The tiles on the maps that represent your devices also show the overall status of a location. This is useful for monitoring distributed networks.


A group is an organizational unit in the device tree that helps to arrange your devices. You can add devices or additional subgroups to existing groups. This way, you can model your physical network's topology within the PRTG configuration. You can use groups to arrange similar objects so that they inherit the same settings.

Hosted Probe

The hosted probe relates to PRTG hosted by Paessler like the local probe relates to PRTG on premises. When creating a PRTG hosted by Paessler instance, the system automatically adds the hosted probe. The hosted probe always runs on the PRTG core server system that we host for you and it shows the monitoring values of your PRTG instance hosted by Paessler. You can use the hosted probe to monitor devices, servers, and services that are publicly available in the internet like, for example, websites. To monitor your LAN, you need at least one remote probe installation in your network. The local probe is not available in PRTG hosted by Paessler.


A library is a way to show parts of your device tree in a different layout or using different filters. An editor is available that lets you create libraries directly in your browser.

Library Node

Libraries use library nodes to reference objects in your monitoring setup. Library nodes can show a subtree of the device tree in the library or they can show a collection of filtered sensors in the library.

Local Probe

When installing PRTG on premises, the local probe is installed together with the PRTG 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. If you use PRTG hosted by Paessler, the hosted probe replaces the local probe. There are some differences between PRTG hosted by Paessler and PRTG on premises.


PRTG uses lookups for some sensor types and for some sensors with custom channels. In general, lookups translate map status values as returned by a device (usually integers) to more informative expressions in words.


Maps (sometimes referred to as dashboards) are a way to present monitoring data the way you want it. An editor is available that lets you create maps directly in your browser. Using maps, you can also make your overview pages of live data publicly available.

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, which distributes the changes among all other nodes in real time.


Sensors that use the meta-scan function, for example SNMP sensors, first look at the device to find what can be monitored. This can be tables, object identifiers (OID), or disks, for example. When the meta-scan is done, the second step of the Add Sensor dialog shows you the parameters that you can monitor. Some sensors require basic information before they can perform a meta-scan. Provide the requested information, such as credentials, in the appearing window. PRTG then scans and recognizes all parameters available for monitoring based on your input.

Mini Probe

With a PRTG Mini Probe, you can create small probes on any device (not just on Windows systems).


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


PRTG uses notifications to send you alerts whenever PRTG discovers a defined status, such as slow or failing sensors, or when sensor channels breach threshold values. You can define an unlimited number of notifications. You can use one or more of several communication channels like email, text messaging, push notifications to Android and iOS devices, and many more.


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

Object Hierarchy

All objects are arranged in a hierarchical order called the object hierarchy, which helps you navigate and arrange settings. The object hierarchy is used to define common settings for groups of objects.

Object Selector

The object selector enables you to browse all objects in your configuration and select an object in two steps. The left-hand side shows your device tree. If you have selected a device, the right-hand side shows the sensors on the device.

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 rejoins the cluster.


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

Probe Device

The probe device is an internal system device that PRTG automatically adds to the local probe. It has access to the probe system and monitors its health parameters using several sensors.

Probe System

A probe system is the system, or computer, that runs a probe. A remote probe, a cluster probe, and the local probe run on a probe system.

PRTG Administration Tool

The PRTG Administration Tool is part of your PRTG installation and helps you to edit the administrative settings of your local probe and your remote probe installations. You can launch the PRTG Administration Tool from the Windows start menu on your PRTG core server or on your remote probe server.

PRTG Application Programming Interface (PRTG API)

The PRTG API enables you to access monitoring data and manipulate objects using HTTP requests, run your own written sensors and notifications, and implement Mini Probes.

PRTG Cloud

The PRTG Cloud is used by the Cloud HTTP sensor and the Cloud Ping sensor to monitor the loading times of a web server via HTTP or the Transmission Control Protocol (TCP) ping times to a parent device from different locations worldwide. PRTG also sends push notifications and securely transmits support bundles to Paessler via the PRTG Cloud.

PRTG Core Server

The PRTG core server is the central unit of PRTG. It receives monitoring data from the probes and handles reporting and notifications, provides the web server for the user interfaces, and much more. In a cluster, one PRTG core server is installed on every node. The PRTG core server is configured as a Windows service that is permanently run by the Windows system without requiring a user that is logged in.

PRTG Desktop

PRTG Desktop is an alternative interface that you can use to connect to the PRTG core server or a PRTG hosted by Paessler instance to configure your setup, view monitoring results, and keep an eye on your network. It is a cross-platform application for fast access to data and monitoring management.

PRTG hosted by Paessler

PRTG hosted by Paessler is the PRTG cloud solution where we at Paessler run the PRTG core server and hosted probe for you. No PRTG core server installation inside your network is necessary. The PRTG web interface for monitoring configuration and reviewing monitoring data is the same for both PRTG hosted by Paessler and PRTG on premises.

PRTG on premises

PRTG on premises is a network monitoring application for Windows-based systems with which you can monitor your entire network. A PRTG core server installation inside your network is necessary. The PRTG web interface for monitoring configuration and reviewing monitoring data is the same for both PRTG on premises and PRTG hosted by Paessler.

Recommended Sensors Detection

PRTG uses the recommended sensors detection to analyze devices in your network and to suggest sensors that are still missing for a complete monitoring setup. The analysis runs with low priority in the background when you add a new device, when the last analysis was executed more than 30 days ago, or when you manually start it.

Release Channel

PRTG updates are delivered in different release channels. With PRTG on premises, you can choose between maximum stability (Stable), or most early access to new features (Canary or Preview). PRTG hosted by Paessler does not have release channels. Instead, we roll out the latest stable version to PRTG hosted by Paessler instances in stages, so your instance automatically updates to the latest stable version.

Remote Probe

A remote probe is a small piece of software installed on a computer, or probe system, in the local or remote network. It scans the network from there and sends monitoring results to the PRTG core server. Once the connection is established, the remote probe is shown in the device tree. All objects created on the remote probe, or below it in the device tree, are monitored by the remote probe system. You can add groups and devices to the probe. In a cluster, remote probes can connect to all cluster nodes so you can view monitoring data of a probe on all nodes.

Root Group

The root group is the topmost instance in the object hierarchy of PRTG. It contains all other objects in your setup. All other objects inherit the settings of the root group.


You can use schedules to pause monitoring or notifications for certain time periods or at certain times. You can also use schedules to define the time periods that are covered when creating reports.


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. Monitoring the CPU load of the local system is done by yet another sensor, and so on. The data of sensors is shown in their respective channels. Each sensor has at least one channel.

Sensor States

The color of a sensor represents its status. There are 8 different sensor states: Down, Down (Partial), Down (Acknowledged), Warning, Unusual, Up, Paused, and Unknown.

Sensor Tree

Sensor tree is a synonym for device tree.

Similar Sensors Detection

Similar sensors detection enables PRTG to analyze sensor data for similarities. The detection runs in the background with low priority. The recommended setting for similar sensors detection is to let PRTG automatically decide how many channels it analyzes.


Tickets are created by the system or by a PRTG user and contain important messages or action steps for the administrator or another specific user to take. Every ticket should be viewed to take appropriate action. You can access the list of tickets from the main menu.


Packet Sniffer and xFlow (NetFlow, jFlow, sFlow, IPFIX) sensor types can break down traffic by IP address, port, protocol, and other parameters. The results are shown in graphs that are known as Toplists.


PRTG sends a notification when a defined event evokes it. These events are known as triggers. The following events can trigger notifications: sensor status changes, sensor value threshold breaches, speed threshold breaches, volume threshold breaches, and sensor value changes.

Unusual Detection

The unusual detection can set sensors to an Unusual status when there are values that are untypical for the time span in which they are measured. PRTG compares the current average values to the historic monitoring results for this purpose. If the current values show a big difference to the values that are normally retrieved by a sensor, this sensor indicates this with the Unusual status.


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