Paessler PRTG

Professional host and
server monitoring software


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    PRTG monitors your
    mail servers

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    PRTG monitors your
    web servers
  • icon check white 2
    PRTG monitors your
    database servers

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    PRTG monitors your
    virtual servers

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    PRTG monitors ALL your servers and hosts. 24/7. At a glance.



Why is server monitoring important?

Servers are the backbone of your business. To minimize downtime and to ensure peak performance of your website and services, constant monitoring of your server infrastructure and your data center is vital.
By tracking the uptime, health, disk space and performance of your servers, you can prevent outages and identify bandwidth hogs. In addition, you are laying the foundation for delivering a great service to your customers, through a fast-loading and constantly available website.


Professional unified server monitoring software: That's PRTG

PRTG monitors all types of servers – even in distributed networks.
Here are a few examples of the kinds of servers for which PRTG provides predefined
sensors so you can get started with your server monitoring at once:


 i How PRTG defines sensors

In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, e.g. the traffic of a switch port, the CPU load of a server, the free space of a disk drive. On average you need about 5-10 sensors per device or one sensor per switch port.

View video (3:26 min.)


Mail server monitoring

Mail servers, in particular, are sensitive issues for companies. When mail server glitches occur, employees are quick to complain, putting the support department under intense strain. With PRTG, you can monitor your mail servers permanently and be alerted in a timely fashion. IMAP, POP3, SMTP, and many more: we supply more than a dozen sensors for your mail server monitoring.

Sensors for mail server monitoring

Web Server Monitoring

Web server monitoring

Website performance is a deciding factor for many companies – all the more so when they offer products and services via their websites. Downtime is costly, right from the very first second. That’s why PRTG also makes a whole range of sensors available for your web server monitoring (IIS, Apache, and more).

Sensors for web server monitoring

Database Server Monitoring

Database server monitoring

Practically all company information is stored in databases. When it comes to databases, performance is also the basis for the effective functioning of each and every department. PRTG thus offers a variety of sensors which are available for immediate use. These include sensors for the monitoring of MySQL, Microsoft SQL, and Oracle SQL. You can selectively choose HTTP content or perform database queries.

Sensors for database server monitoring

File Server Monitoring

File server monitoring

If firms can’t access information, then nothing works. One of the tasks of administrators is therefore to ensure the file server runs smoothly, and as with other servers, avoid crashes. It’s not uncommon for administrators to search, say, for a specific FTP server monitoring tool. But PRTG has you fully covered in this area as well. For you get around 20 sensors just for your file server monitoring. Monitoring of NAS devices and storage area networks (SAN) is also supported by PRTG. 

Sensors for file server monitoring

More server monitoring sensors

Monitor as many servers as you like...

With PRTG, you get a number of other predefined sensors which provide an overview of your entire server landscape in no time at all. You can create your own sensors whenever you want, and use the API to adapt PRTG to absolutely any special situation.

More server sensors


Bluescreen? This short video explains why server monitoring is important


Want to know in detail, what a server is? Read on!

What is a server?

what is a server

A server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network. In theory, whenever computers share resources with client machines they are considered servers. There are many types of servers, including web servers, mail servers, and virtual servers.

An individual system can provide resources and use them from another system at the same time. This means that a device could be both a server and a client at the same time.

Some of the first servers were mainframe computers or minicomputers. Minicomputers were much smaller than mainframe computers, hence the name. However, as technology progressed, they ended up becoming much larger than desktop computers, which made the term microcomputer somewhat farcical.

Initially, such servers were connected to clients known as terminals that did not do any actual computing. These terminals, referred to as dumb terminals, existed simply to accept input via a keyboard or card reader and to return the results of any computations to a display screen or printer. The actual computing was done on the server.

Later, servers were often single, powerful computers connected over a network to a set of less-powerful client computers. This network architecture is often referred to as the client-server model, in which both the client computer and the server possess computing power, but certain tasks are delegated to servers. In previous computing models, such as the mainframe-terminal model, the mainframe did act as a server even though it wasn’t referred to by that name.

As technology has evolved, the definition of a server has evolved with it. These days, a server may be nothing more than software running on one or more physical computing devices. Such servers are often referred to as virtual servers. Originally, virtual servers were used to increase the number of server functions a single hardware server could do. Today, virtual servers are often run by a third-party on hardware across the Internet in an arrangement called cloud computing.

A server may be designed to do a single task, such as a mail server, which accepts and stores email and then provides it to a requesting client. Servers may also perform several tasks, such as a file and print server, which both stores files and accepts print jobs from clients and then sends them on to a network-attached printer.

How a server works

how a server works 

To function as a server, a device must be configured to listen to requests from clients on a network connection. This functionality can exist as part of the operating system as an installed application, role, or a combination of the two.

For example, Microsoft’s Windows Server operating system provides the functionality to listen to and respond to client requests. Additionally installed roles or services increase which kinds of client requests the server can respond to. In another example, an Apache web server responds to Internet browser requests via an additional application, Apache, installed on top of an operating system.

When a client requires data or functionality from a server, it sends a request over the network. The server receives this request and responds with the appropriate information. This is the request and response model of client-server networking, also known as the call and response model.

A server will often perform numerous additional tasks as part of a single request and response, including verifying the identity of the requestor, ensuring that the client has permission to access the data or resources requested, and properly formatting or returning the required response in an expected way.

Types of servers

Types of servers 

There are many types of servers that all perform different functions. Many networks contain one or more of the common server types:

File servers

File servers store and distribute files. Multiple clients or users may share files stored on a server. In addition, centrally storing files offers easier backup or fault tolerance solutions than attempting to provide security and integrity for files on every device in an organization. File server hardware can be designed to maximize read and write speeds to improve performance.

Print servers

Print servers allow for the management and distribution of printing functionality. Rather than attaching a printer to every workstation, a single print server can respond to printing requests from numerous clients. Today, some larger and higher-end printers come with their own built-in print server, which removes the need for an additional computer-based print server. This internal print server also functions by responding to print requests from a client.

Application servers

Application servers run applications in lieu of client computers running applications locally. Application servers often run resource-intensive applications that are shared by a large number of users. Doing so removes the need for each client to have sufficient resources to run the applications. It also removes the need to install and maintain software on many machines as opposed to only one.

DNS servers

Domain Name System (DNS) servers are application servers that provide name resolution to client computers by converting names easily understood by humans into machine-readable IP addresses. The DNS system is a widely distributed database of names and other DNS servers, each of which can be used to request an otherwise unknown computer name. When a client needs the address of a system, it sends a DNS request with the name of the desired resource to a DNS server. The DNS server responds with the necessary IP address from its table of names.

Mail servers

Mail servers are a very common type of application server. Mail servers receive emails sent to a user and store them until requested by a client on behalf of said user. Having an email server allows for a single machine to be properly configured and attached to the network at all times. It is then ready to send and receive messages rather than requiring every client machine to have its own email subsystem continuously running.

Web servers

One of the most abundant types of servers in today’s market is a web server. A web server is a special kind of application server that hosts programs and data requested by users across the Internet or an intranet. Web servers respond to requests from browsers running on client computers for web pages, or other web-based services. Common web servers include Apache web servers, Microsoft Internet Information Services (IIS) servers and Nginx servers.

Database servers

The amount of data used by companies, users, and other services is staggering. Much of that data is stored in databases. Databases need to be accessible to multiple clients at any given time and can require extraordinary amounts of disk space. Both of these needs lend themselves well to locating such databases on servers. Database servers run database applications and respond to numerous requests from clients. Common database server applications include Oracle, Microsoft SQL Server, DB2, and Informix.

Virtual servers

Virtual servers are taking the server world by storm. Unlike traditional servers that are installed as an operating system on machine hardware, virtual servers exist only as defined within specialized software called hypervisor. Each hypervisor can run hundreds, or even thousands, of virtual servers all at once. The hypervisor presents virtual hardware to the server as if it were real physical hardware. The virtual server uses the virtual hardware as usual, and the hypervisor passes the actual computation and storage needs onto the real hardware beneath, which is shared among all the other virtual servers.

Proxy servers

A proxy server acts as an intermediary between a client and a server. Often used to isolate either the clients or servers for security purposes, a proxy server takes the request from the client. Instead of responding to the client, it passes the request on to another server or process. The proxy server receives the response from the second server and then replies to the original client as if it were replying on its own. In this way, neither the client nor the responding server needs to directly connect to each other.

Monitoring and management servers

Some servers exist to monitor or manage other systems and clients. There are many types of monitoring servers. Several of them listen to the network and receive every client request and server response, but some do not request or respond to data themselves. In this way, the monitoring server can keep track of all the traffic on the network, as well as the requests and replies of clients and servers, without interfering with those operations. A monitoring server will respond to requests from monitoring clients such as those run by network administrators watching the health of the network.

Server structures

Server structures

The concept of servers is nearly as old as networking itself. After all, the point of a network is to allow one computer to talk to another computer and distribute either work or resources. Computing has evolved since then, resulting in several types of server structures and hardware.

Mainframe or minicomputer (AS/400)

You could say that the original servers, mainframe computers, and later, minicomputers, handled almost all computing tasks except the interaction with the user through a screen and keyboard, which was left to the client system.

Computer hardware server

The next major wave of servers included computer-based servers. In many respects, these servers were nothing more than larger, more powerful desktop computers. Such servers were generally more expensive and held far more memory and disk space than most client computers. Each server was still a self-contained unit with its own motherboard, processor, memory, disk drives, and power supply. Servers like this were often warehoused in air-conditioned rooms called server rooms, and were later bolted into racks for better storage and accessibility.

Blade servers

The original computer server hardware was large and stored in racks that could hold hundreds of pounds. Over time, however, faster means of connecting hardware resulted in parts of the server being extracted from a single self-contained device. By removing hard drives, eliminating internal cooling, and the ongoing miniaturization of computing parts, servers were eventually reduced to a single thin server known as a blade server. While still stored in racks in server rooms, blade servers are smaller and can be replaced more easily.

Combining servers

Even before virtualization, servers were being extracted from the standard model of a single server operating system installed on a hardware machine. Technology, such as network-attached storage, removed the need for a server to have its own storage. Other technologies, such as mirroring and clustering, enabled pieces of hardware to be combined into larger, more powerful servers. Such a server might consist of several blades, several attached storage devices, and an external power supply, and each piece could be swapped out for another while the server was still running.

Virtual servers

Virtual Servers still require hardware, but that hardware now runs a different process known as a hypervisor. In some cases, such as Microsoft’s Hyper-V, a full operating system continues to run on the hardware itself. In other cases, so-called bare-metal hypervisors can be installed directly onto server hardware. In both instances, the hardware itself is often spread across an array of blade servers, networked storage, and power supply, resulting in an environment where it is impossible to tell where any individual server ends and another begins.


Examples of server operating systems

Examples of server operating systems

Microsoft Windows servers

An argument can be made that Windows for Workgroups was Microsoft’s first server operating system. In that version, certain computers could be set to share resources and respond to requests from clients, which made them servers by definition. Microsoft’s first real server operating system was Windows NT. Its 3.5 and 3.51 versions ran on many business networks until Microsoft released its Windows Server line that continues to exist today. The most current Windows Server version is Windows Server 2016. This version supports numerous applications and databases as well as a hypervisor that allows virtual servers.

Linux / Unix servers

The other major player in server operating systems is the Linux/Unix realm. There are multiple versions and flavors of Linux/Unix including Red Hat Enterprise Linux, Debian, and CentOS. As an open-source operating system, Linux is very popular as a web server, often with the Apache web application server installed.


Although no longer made, NetWare was a major player in the server software space as the client-server era was ramping up. Eventually, NetWare moved its server operating system to a Linux-based kernel and named it a Novell Open Enterprise Server (OES).

Cloud servers

Virtual servers hosted on a third-party infrastructure on an open network, such as the Internet, are called cloud servers. There are numerous cloud server providers these days, including Google’s Cloud Platform, Microsoft Azure, and IBM Cloud.
However, the main pioneer of corporate cloud computing was Amazon’s AWS platform. It originally started using spare capacity of Amazon’s own servers and networks, but AWS now allows customers to create a virtual server nearly instantly and then adjust the amount of resources that server may use on the fly.
Today, a server can be nothing more than the data of physical hardware that consists of multiple processors, disk drives, memory, and network connections. But, even now, a server is still just a system that responds to a request from a client.



Defining and understanding server monitoring

Information in real time

Server monitoring lets you monitor your servers in real time with regard to availability, accessibility, capacity, and overall reliability. With server monitoring, your servers are checked at regular intervals to ensure you always know their status.

Improve stability

Sysadmins monitor their servers because they wish to improve the stability and performance of their networks. If certain threshold values are exceeded, you’ll receive a warning message so you can take action at once. Our monitoring service helps you complete your everyday tasks. It provides you with a constant overview of your server resources.

Basis for analysis

Sysadmins analyze the values they receive from their monitoring software to develop courses of action. When studied over the long term, these values can help optimize various aspects that are responsible for the performance of your network, such as capacity planning. The PRTG reports feature is extremely useful for such optimization.


quote markus puke

“We can all work with greater peace of mind knowing
that our systems are constantly being monitored.”

Markus Puke, Network Administrator, Schüchtermann Klinik, Germany


3 good reasons for PRTG as your server monitoring software

 iA server is a computer or system that provides resources, data, services, or programs to other computers, known as clients, over a network. In theory, whenever computers share resources with client machines they are considered servers. There are many types of servers, including web servers, mail servers, and virtual servers.
Read more

An Integrated Solution

An integrated solution

Whether just a few servers or a large server farm: PRTG adapts dynamically to the size of your server landscape. And should you acquire more servers, all licenses are individually upgradeable. PRTG is an integrated solution: whether processors, memory, cooling fans, power supplies, or other components, our Server Monitoring Tool simultaneously monitors your servers as well as your entire infrastructure. PRTG immediately recognizes if a router or switch fails and causes a disruption in the server. Even virtual servers are recognized automatically and included in the monitoring.

Prompt Alerts

Prompt alerts

Servers are the main elements of every IT infrastructure. Without them, a company is more or less unable to function. PRTG ensures system failures are as short-lived as possible – or even prevented in advance! Thanks to the e-mail or SMS alert feature, you’ll know straight away if complications arise. Locate errors directly: this will save you lots of time. You can even define the alert threshold values yourself. This means you’ll be notified before a shortage leads to a crash.

Capacity planning

Capacity planning

PRTG helps out with your capacity planning. Our Server Monitoring Tool lets you to promptly recognize when in the medium to long-term it will be necessary to increase your capacities. Our dashboard presents compelling charts which are perfect for convincing your higher-ups with no technical know-how to expand your resources. The tool also features detailed reports providing a basis for scheduling and continual process optimization.


5 common questions regarding server monitoring 

1. How can I best protect my company from server failures?

When a server goes down, the IT department must take action quickly. PRTG helps you improve the reliability of your servers. If the load of individual hardware components such as CPU, hard drives, or RAM rises, you’ll be notified at once. With PRTG, all threshold values are customizable.

2. Can I monitor external servers from one central location?

PRTG can monitor your servers from one centralized location, even if your devices are in different parts of the world. To do so, the monitoring tool uses “remote probes.” Remote probes allow for agentless monitoring, which means you can monitor IT environments found in different locations than your own.

3. What kind of information is collected by a server monitoring tool?

There are many monitoring and analysis tools on the market. We recommend weighing the pros and cons of each (such as PRTG vs. Nagios). PRTG is a network monitoring tool that continually monitors your entire IT environment. This environment includes servers, as well as devices such as switches and routers from all the major manufacturers. Add to that bandwidth, applications, quality of service, and much more.

4. How does the alarm get triggered when a server malfunctions or goes down?

You yourself set the threshold values which, when exceeded, activate the sending of a warning message. You can also define how the message is sent. Options include email, push notification, SMS, syslog messages, and more. The PRTG alarm is fully customizable. You can, for example, set up a more rigorous notification system for critical infrastructures (such as your servers) than for individual workstations.

5. Will monitoring have a negative impact on the performance of my network?

Our sensors use a variety of protocols to monitor your network. These include SNMP, WMI, and performance counters. Windows Management Instrumentation (WMI) is a commonly used standard created by Microsoft. Running WMI often puts great strain on a network’s load. If you decide to go with WMI, you’ll want to create as few WMI sensors as possible to ensure you don’t compromise the performance of your network. By contrast, the load generated by SNMP is quite insignificant, even for extensive monitoring with several thousand sensors. You’ll therefore rarely encounter drops in performance.


HP Enterprise Partner

Thanks to our multi-purpose monitoring tool and the comprehensive support we offer for HP products, we have been asked to participate in the Hewlett Packard Enterprises Partner Ready for Technology Partner Program. This partnership with Hewlett Packard Enterprises helps us to effectively develop new solutions, all the while improving existing software and making our products more beneficial for users. Our technology partnership with HPE is also indicative of the fact that PRTG runs well with HPE ProLiant servers, HPE BladeSystems, and other software created by the manufacturer.


Virtual server monitoring included

In many companies, virtual servers are already a part of the IT structure. And for good reason: memory, hard disk space, and computing power can be allocated to individual applications dynamically. Resources are thus used in a considerably more efficient manner. PRTG monitors your virtual servers, right down to the very last detail.

More about Virtual Server Monitoring >>


PRTG makes your job easier

Our monitoring software frees you to focus on other tasks by promptly notifying you of potential issues.


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Save effort

PRTG gives you one central monitoring tool for your servers and entire network. Enjoy a quick overview of your whole infrastructure via our dashboard and app.

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Save time

Getting started with PRTG is a breeze. Setting up or switching from another network monitoring tool is easy thanks to the auto-discovery and pre-configured device templates.

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Save money

80% of our customers report substantial cost savings with network monitoring. Your costs of licenses will likely pay for themselves within weeks.



Try our multi server simulator!

Would you like to set up a collection of new servers but first test the behavior of your network? Then use our Multi Server Simulator! See how your network reacts – and which areas need work.

To Multi Server Simulator


Predefined sensors for server products

PRTG includes predefined sensors for server computers of different vendors.


Here's what server monitoring looks like in PRTG


HTTP server error messages

Common server errors

All status codes beginning with “5” (5XX) are server errors – and therefore a problem. Server error 500 is a collective status code for unexpected server errors. All other server errors (501, 502, 503, etc.) are used to flag specific problems. Error 503, for example, means the website’s web server is currently overloaded or unavailable. For more information, see our knowledge base articles on HTTP status codes and sensors: Which HTTP status code leads to which HTTP sensor status? and Can I check for specific HTTP response codes with PRTG?

Web server monitoring

Error messages are clear evidence that web server monitoring makes sense. All the more so if the website is an important tool for the company. PRTG comes with a full range of HTTP sensors for monitoring websites as well as individual URLs.


Your options: Free server monitoring or a license?

Server monitoring freeware

Server monitoring freeware

You’re welcome to try the full version of PRTG for 30 days for free. After the first month, you can continue to use 100 sensors for as long as you like. For each of your devices, you’ll need around 10 sensors. The 100 free sensors are yours to choose however you please. These sensors often suffice for setting up basic server monitoring. If you have a small network, then the free version may be all you ever need. What’s more, the alarm and reports features are included.

Our licenses

Our licenses

PRTG offers a variety of different licenses. Each of these licenses gives you access to a specific number of sensors. If you need more sensors, you can simply upgrade your license. Any existing monitoring will remain unchanged. Many sysadmins start out with the free trial version. This lets you get a feel for the monitoring tool with no strings attached.


arne seifert

„Hey Arne, how do I avoid false alarms during server maintenance?“

“In practice, repairs in the short-term will be necessary. While working, your monitoring will not trigger false alarms. The one-time maintenance window allows you to pause monitoring for each individual device or device group. For regular maintenance, with PRTG you can easily create an automated schedule.”

Arne Seifert, technical support at Paessler AG


See what PRTG can do as your virtual server monitor

Overview Server monitoring


Virtualized servers come with greater complexity: when malfunctions occur at the hardware level, virtual machines are also affected. With PRTG, you get a complete overview at all times. PRTG is a monitoring solution for your entire infrastructure. Create a foundation that enables your efficient data structures to run as smoothly as possible – and watch as the improved utilization pays off.

Custom Fit server monitor

Custom Fit

There are a great many virtual environments. PRTG can monitor almost every single one. PAESSLER AG is a VMware technology partner. Our Server Monitoring Tool offers predefined sensors which are automatically applied. Find more information on VMware Monitoring with PRTG. Many different virtual environments can be monitored by PRTG, such as Hyper-V, XEN, Parallels Virtuozzo Containers, Amazon EC2, and many more.

Flexible server monitoring


Virtual servers are often introduced when a company is in the midst of quick and vigorous growth. New system services must be installed without too much expense. PRTG is fast and easy to upgrade. It adapts to your growth dynamically. New sensors can be applied in just a few minutes and with next to no effort at all. This makes managing the server monitoring tool a real breeze.


Host monitoring for virtual servers

Especially in virtual environments, it's important to monitor all your hosts. Host monitoring with PRTG allows you to constantly keep track of the availability and performance of your host. Especially when there are multiple VMs running one host, it's absolutely crucial to ensure a proper allocation of the resources.

Host monitoring can also be important for web servers.

Whether you want to monitor physical or virtual servers, with PRTG you always keep an eye on the proper functioning of your hosts.


LDAP monitoring with PRTG

LDAP at a glance

Lightweight Directory Access Protocol (LDAP) is a protocol that queries information from distributed directory services. Directories contain object-related data which can be read by monitoring tools such as PRTG. One such directory is Active Directory, the Microsoft service created for use in a Windows server environment.

Getting started with LDAP monitoring

PRTG comes with an LDAP sensor. This sensor attempts to connect to the LDAP server using authentication via the distinguished name (DN), and displays the response time of your LDAP server in the event that the connection and authentication are successful. Note: the LDAP Sensor cannot use LDAP via SSL. For more information, see the log monitoring page on our website.


Also interesting

From PRTG 21.3.70 on, we released our first Redfish sensors.

With Redfish sensors, you can monitor server hardware in the datacenter using the Redfish protocol from the servers' management controllers like Lenovo XClarity, HPE iLO, or Dell iDrac. Redfish is the successor of IPMI and provides better security.

Redfish System Health sensor

This sensor monitors the overall system status and the status of various components such as power supplies or PCIe devices, if available.

Redfish Virtual Disk sensor

This sensor monitors the virtual disk of a Redfish Scalable Platforms Management API (Redfish)-capable server.

Redfish Power Supply sensor

This sensor monitors the power supply of a Redfish Scalable Platforms Management API (Redfish)-capable server.


Create innovative solutions with Paessler’s IT partners

Partnering with innovative IT vendors, Paessler unleashes synergies to create
new and additional benefits for joined customers.


The PRTG SLA plugin from CORP IT, allows monitoring data in PRTG to be extracted and pulled into your existing SLA reporting tools, such as SQL Server Reporting Engine or Crystal Reports.

Read more


With ScriptRunner, Paessler integrates a powerful event automation platform into PRTG Network Monitor.

Read more


UVexplorer integrates tightly with PRTG to bring fast and accurate network discovery, detailed device inventory, and automatic network mapping to the PRTG platform.

Read more


You want to know more about
other monitoring topics?

Hard disk monitoring

How’s the hard disk holding up? Is there enough free space on your servers and workstations? 

Learn more

Security monitoring

PRTG allows you to improve security by identifying weak spots and loopholes. To do so, it monitors your ports and servers (among other things). 

Learn more


Still not convinced?



More than 500,000 sysadmins love PRTG

Paessler PRTG is used by companies of all sizes. Sysadmins love PRTG because it makes their job a whole lot easier.

Still not convinced?


Monitor your entire IT infrastructure

Bandwidth, servers, virtual environments, websites, VoIP services – PRTG keeps an eye on your entire network.



Try Paessler PRTG for free

Everyone has different monitoring needs. That’s why we let you try PRTG for free. Start now with your trial.




Network Monitoring Software - Version (November 7th, 2022)


Download for Windows and cloud-based version PRTG Hosted Monitor available


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Up to 100 sensors for free (Price List)

Unified Monitoring

Network devices, bandwidth, servers, applications, virtual environments, remote systems, IoT, and more

Supported Vendors & Applications

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