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

This section explains PRTG-specific terminology.



The alarms list shows all sensors that are in the Down, Down (Partial), Down (Acknowledged), Warning, or Unusual status. The alarms list shows you 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 a master node and one or more failover nodes. Every cluster node can monitor every device in a network for fail-safe monitoring.

Cluster node

Cluster nodes make up a cluster. Cluster nodes can be master nodes or failover nodes.

Cluster probe

When you create or join a cluster, 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 cluster nodes. Create or move objects there for fail-safe monitoring. If one cluster node fails, the other cluster nodes continue to monitor all objects. You can add groups and devices to the cluster probe. The cluster probe runs as part of the local probe.

Cluster probe device

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



A preconfigured sample dashboard is 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 the Maps feature.


A device represents a physical or virtual component in your network that is reachable via an IP address. For a clear device tree structure, you usually create one device 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 a device in the device tree. When you create a device template, PRTG saves information for nearly all sensors on the device to a template file. You can later use the template file 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 monitoring 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 becomes a failover master node. The failover master node takes over the role of the primary master node until it reconnects to the cluster.

Failover node

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


PRTG supports NetFlow v5, NetFlow v9, IPFIX, sFlow v5, and jFlow v5.



A gauge is a type of visual representation of the values of a channel. The gauge needle points to the current value of the channel. Other types of visual representations are toggles and switches.

Geo Maps

The Geo Maps feature shows the different locations of your devices on a geographical map using the location data that you provide in the settings of probes, groups, or devices. The status icons on the geographical 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. You can add devices or subgroups to 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 in PRTG Hosted Monitor is like the local probe in PRTG Network Monitor. When you create a PRTG Hosted Monitor instance, the system automatically adds the hosted probe. The hosted probe runs on the PRTG core server system that we host for you and it shows the monitoring values of your PRTG Hosted Monitor instance. You can use the hosted probe to monitor devices, servers, and services that are publicly available on 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 Monitor.



A library enables you to create additional views of your device tree. These views are updated in the same scanning interval as your device tree and show the same monitoring data, but arranged the way you want. This is useful if you want to display data in different ways, like depending on target groups or a specific use case.

Library node

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


Limits let you define thresholds for channel values. When the value of a channel is above or below the defined limit, the sensor can show the Warning or Down status.

Local probe

When installing PRTG Network Monitor, the local probe is installed together with the PRTG core server. All objects created on the local probe, or underneath it in the device tree, are monitored by the local PRTG core server system. You can add groups and devices to the local probe. If you use PRTG Hosted Monitor, the hosted probe replaces the local probe.

Local probe device

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


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



The Maps feature lets you present monitoring data the way you want it. An editor is available that lets you create maps (sometimes referred to as dashboards) directly in your browser. Using maps, you can also make overviews 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 cluster nodes in real time. There are two types of master nodes: primary master node and failover master node.


Sensors that use the meta-scan feature, for example SNMP sensors, first look at the according device to find what they can monitor. This can be tables, object identifiers (OID), or disks, for example. When the meta-scan is finished, 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 dialog box. PRTG then scans and recognizes all parameters that are available for monitoring based on your input.

Mini probe

With a mini probe, you can create small probes on any device (not only on Windows systems).



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

Notification trigger

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



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. The object hierarchy is used to define common settings for groups of objects.

Object selector

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


Primary group

Every user has to be a member of a primary group to make sure there is no user without group membership. Membership in other user groups is optional.

Primary master node

In a cluster, the primary master node is the cluster node that is the master node by configuration.


A probe is where the actual monitoring takes place. There are local probes, cluster probes, remote probes, and hosted probes.

Probe device

The probe device is an internal system device that PRTG automatically adds to the 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 Windows 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. You can use it to edit the administrative settings of the local probe and remote probe installations. You can start the PRTG Administration Tool from the Windows Start menu on the PRTG core server system or on the remote probe system.

PRTG Application Programming Interface (PRTG API)

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

PRTG Cloud

The PRTG Cloud is used by the Cloud HTTP v2 sensor and the Cloud Ping v2 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 probe 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 cluster 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 core server service

The PRTG core server service is responsible for running the PRTG core server. It is a Windows service that permanently runs on the PRTG core server system.

PRTG core server system

The PRTG core server system is the system, or Windows computer, that runs the PRTG core server.

PRTG data directory

The PRTG data directory is the directory on the PRTG core server system or remote probe system where PRTG stores monitoring data, configuration data, and logs.

PRTG app for desktop

PRTG app for desktop is an alternative interface that you can use to connect to the PRTG core server or a PRTG Hosted Monitor 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 Monitor

PRTG Hosted Monitor is the PRTG cloud solution where we at Paessler run the PRTG core server and hosted probe for you. PRTG Hosted Monitor does not require a PRTG core server installation inside your network.

PRTG Network Monitor

PRTG Network Monitor is a network monitoring application for Windows-based systems with which you can monitor your entire network. PRTG Network Monitor requires a PRTG core server installation inside your network.

PRTG probe service

The PRTG probe service is responsible for running a probe. It is a Windows service that permanently runs on the probe system.

PRTG program directory

The PRTG program directory is the directory on the PRTG core server system where PRTG stores all files that are required for it to run.

PRTG web interface

The PRTG web interface is the Asynchronous JavaScript and XML (AJAX) based web interface of PRTG. It is the default interface for setting up your monitoring.


Recommended Sensors Detection

The Recommended Sensors Detection feature enables PRTG to analyze devices in your network and to suggest sensors that are still missing for a comprehensive monitoring setup. If enabled, the analysis runs in the background with low priority if you add a new device, if the last analysis was executed more than 30 days ago, or if you manually start it.

Release channel

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

Remote probe

A remote probe is a small piece of software that is installed on a computer, or remote probe system, in the local or remote network. It scans the network and sends monitoring results to the PRTG core server. Once the connection has been established, the remote probe is shown in the device tree. All objects that you create 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 remote probe. In a cluster, remote probes can connect to all cluster nodes so you can view monitoring data of a remote probe on all cluster nodes.

Remote probe device

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

Remote probe system

The remote probe system is the system, or Windows computer, that runs a remote probe.

Root group

The root group is the topmost instance in the object hierarchy in the device tree. It contains all objects in your monitoring setup. All objects inherit the settings of the root group by default.



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


A sensor monitors one aspect of a device. For example, one sensor monitors if a device responds to a ping request. A different sensor monitors the traffic of one Ethernet port of a router, and so on. The data of sensors is shown in their respective channels. Each sensor has at least one channel.

Sensor status

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

Similar Sensors Detection

The Similar Sensors Detection feature enables PRTG to analyze sensor data for similarities. If enabled, the detection runs in the background with low priority. The recommended setting for the analysis depth is to let PRTG automatically decide how many channels it analyzes.


A switch is a type of visual representation of the values of a channel. Switches represent boolean values when using lookups.



Tickets are created by the system or by a user and contain important messages or action steps for the administrator or other users to take. You should view every ticket to take appropriate action. You can access the list of tickets from the main menu.


A toggle is a type of visual representation of the values of a channel. Toggles represent bitfields when using lookups.


Packet Sniffer and Flow (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 called Toplists.


Unusual Detection

The Unusual Detection feature can set sensors to the Unusual status when it detects values that are not typical for the time span in which they are measured. If the detection is enabled, 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.