Paessler PRTG

All-in-one IP monitor PRTG


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    Professional IP scanning software

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    IP check & ping IP with PRTG
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    Use PRTG as your IP Sniffer and IP traffic monitor







IP/network scanner: Why PRTG is the tool for you!

A convenient overview

A convenient overview

With PRTG, you'll always know the score! Its central dashboard lets you see if everything is in the "green." As soon as problems or failures occur, the view immediately jumps to the "red". Thanks to our apps you get to stay abreast of the current status at all times - even when you're on the go.

Prompt and customizable alarms

Prompt and customizable alarms

PRTG features a built-in notification function. Its alarm is entirely customizable, which means you can decide to be alerted by e-mail, SMS, or page. Configure the alarm so you can be notified promptly – before system failures occur! By doing so, you will increase the reliability of your network.

saving of time

A noticeable saving of time

Paessler regularly carries out customer surveys. One survey result: more than half of our customers indicate that they save two hours or more per week by using PRTG. Over the course of a year, this amounts to around 100 hours. Two full work weeks, which you can use to focus on more important things.


Want to know in detail, what an IP address is? Read on!

What is an IP address?

What is an IP address


An IP address (internet protocol address) is a numerical representation that uniquely identifies a specific interface on the network.

Addresses in IPv4 are 32-bits long. This allows for a maximum of 4,294,967,296 (232) unique addresses. Addresses in IPv6 are 128-bits, which allows for 3.4 x 1038 (2128) unique addresses.

The total usable address pool of both versions is reduced by various reserved addresses and other considerations.

IP addresses are binary numbers but are typically expressed in decimal form (IPv4) or hexadecimal form (IPv6) to make reading and using them easier for humans.

The Internet Protocol (IP)

the Internet Protocol

IP stands for Internet Protocol and describes a set of standards and requirements for creating and transmitting data packets, or datagrams, across networks. The Internet Protocol (IP) is part of the Internet layer of the Internet protocol suite. In the OSI model, IP would be considered part of the network layer. IP is traditionally used in conjunction with a higher-level protocol, most notably TCP. The IP standard is governed by RFC 791.

How IP works

IP is designed to work over a dynamic network. This means that IP must work without a central directory or monitor, and that it cannot rely upon specific links or nodes existing. IP is a connectionless protocol that is datagram-oriented., so each packet must contain the source IP address, destination IP address, and other data in the header to be successfully delivered.

Combined, these factors make IP an unreliable, best effort delivery protocol. Error correction is handled by upper level protocols instead. These protocols include TCP, which is a connection-oriented protocol, and UDP, which is a connectionless protocol.

Most internet traffic is TCP/IP.

IP versions

IP versions

There are two versions of IP in use today, IPv4 and IPv6. The original IPv4 protocol is still used today on both the internet, and many corporate networks. However, the IPv4 protocol only allowed for 232 addresses. This, coupled with how addresses were allocated, led to a situation where there would not be enough unique addresses for all devices connected to the internet.

IPv6 was developed by the Internet Engineering Task Force (IETF), and was formalized in 1998. This upgrade substantially increased the available address space and allowed for 2128 addresses. In addition, there were changes to improve the efficiency of IP packet headers, as well as improvements to routing and security.


IPv4 addresses

IPv4 addresses are actually 32-bit binary numbers, consisting of the two subaddresses (identifiers) mentioned above which, respectively, identify the network and the host to the network, with an imaginary boundary separating the two. An IP address is, as such, generally shown as 4 octets of numbers from 0-255 represented in decimal form instead of binary form.

For example, the address represents the 32-bit binary number 10101000.11010100.11100010.11001100.

The binary number is important because that will determine which class of network the IP address belongs to.

An IPv4 address is typically expressed in dotted-decimal notation, with every eight bits (octet) represented by a number from one to 255, each separated by a dot. An example IPv4 address would look like this:


IPv4 addresses are composed of two parts. The first numbers in the address specify the network, while the latter numbers specify the specific host. A subnet mask specifies which part of an address is the network part, and which part addresses the specific host.

A packet with a destination address that is not on the same network as the source address will be forwarded, or routed, to the appropriate network. Once on the correct network, the host part of the address determines which interface the packet gets delivered to.

Subnet masks

A single IP address identifies both a network, and a unique interface on that network. A subnet mask can also be written in dotted decimal notation and determines where the network part of an IP address ends, and the host portion of the address begins.

When expressed in binary, any bit set to one means the corresponding bit in the IP address is part of the network address. All the bits set to zero mark the corresponding bits in the IP address as part of the host address.

The bits marking the subnet mask must be consecutive ones. Most subnet masks start with 255. and continue on until the network mask ends. A Class C subnet mask would be

IP address classes

Before variable length subnet masks (introduced with RFC-1519 in 1993) allowed networks of almost any size to be configured regardless of the actual address, the IPv4 address space was broken into five classes as follows:


Class Leading
Size of network
bit field
Size of rest
bit field
of networks
per network
Total addresses
in class
Start address End address
Class A 0 8 24 128 (27) 16,777,216 (224) 2,147,483,648 (231)
Class B 10 16 16 16,384 (214) 65,536 (216) 1,073,741,824 (230)
Class C 110 24 8 2,097,152 (221) 256 (28) 536,870,912 (229)
Class D (multicast) 1110 not defined not defined not defined not defined 268,435,456 (228)
Class E (reserved) 1111 not defined not defined not defined not defined 268,435,456 (228)


Class A 

In a Class A network, the first eight bits, or the first dotted decimal, is the network part of the address, with the remaining part of the address being the host part of the address. There are 128 possible Class A networks. to


However, any address that begins with 127. is considered a loopback address.

Example for a Class A IP address:

Class B

In a Class B network, the first 16 bits are the network part of the address. All Class B networks have their first bit set to 1 and the second bit set to 0. In dotted decimal notation, that makes to as Class B networks. There are 16,384 possible Class B networks.

Example for a Class B IP address:

Class C

In a Class C network, the first two bits are set to 1, and the third bit is set to 0. That makes the first 24 bits of the address the network address and the remainder as the host address. Class C network addresses range from to There are over 2 million possible Class C networks.

Example for a Class C IP address:


Class D

Class D addresses are used for multicasting applications. Unlike the previous classes, the Class D is not used for "normal" networking operations. Class D addresses have their first three bits set to “1” and their fourth bit set to “0”. Class D addresses are 32-bit network addresses, meaning that all the values within the range of – are used to uniquely identify multicast groups. There are no host addresses within the Class D address space, since all the hosts within a group share the group’s IP address for receiver purposes.

Example for a Class D IP address:

Class E

Class E networks are defined by having the first four network address bits as 1. That encompasses addresses from to While this class is reserved, its usage was never defined. As a result, most network implementations discard these addresses as illegal or undefined. The exception is, which is used as a broadcast address.

Example for a Class D IP address:


Overview: IP address classes and bit-wise representations

Class A
  0.  0.  0.  0 = 00000000.00000000.00000000.00000000 = 01111111.11111111.11111111.11111111

Class B
128.  0.  0.  0 = 10000000.00000000.00000000.00000000 = 10111111.11111111.11111111.11111111

Class C
192.  0.  0.  0 = 11000000.00000000.00000000.00000000 = 11011111.11111111.11111111.11111111

Class D
224.  0.  0.  0 = 11100000.00000000.00000000.00000000 = 11101111.11111111.11111111.11111111

Class E
240.  0.  0.  0 = 11110000.00000000.00000000.00000000 = 11111111.11111111.11111111.11111111


Private addresses

Within the address space, certain networks are reserved for private networks. Packets from these networks are not routed across the public internet. This provides a way for private networks to use internal IP addresses without interfering with other networks. The private networks are - - -


Special addresses

Certain IPv4 addresses are set aside for specific uses: Loopback address (the host’s own interface) IP Multicast Broadcast (sent to all interfaces on network) 


IPv4 address exhaustion

The original IPv4 specification was designed for the DARPA network that would eventually become the internet. Originally a test network, no one contemplated how many addresses might be needed in the future. At the time, the 232 addresses (4.3 billion) were certainly considered sufficient. However, over time, it became apparent that as currently implemented, the IPv4 address space would not be big enough for a worldwide internet with numerous connected devices per person. The last top-level address blocks were allocated in 2011. 


IPv4 Subnets


IPv6 addresses

To avoid the seemingly reoccurring issue in technology, where a specification’s limitation seems more than sufficient at the time, but inevitably becomes too small, the designers of IPv6 created an enormous address space for IPv6. The address size was increased from 32 bits in IPv4 to 128 bits in IPv6.

The IPv6 has a theoretical limit of 3.4 x 1038 addresses. That’s over 340 undecillion addresses, which is reportedly enough addresses to assign one to every single atom on the surface of the earth.

IPv6 addresses are represented by eight sets of four hexadecimal digits, and each set of numbers is separated by a colon. An example IPv6 address would look like this:


IPv6 address abbreviation

With IPv6 addresses being so long, there are conventions to allow for their abbreviation. First, leading zeros from any one group of numbers may be eliminated. For example, :0033: can be written as :33:

Second, any consecutive sections of zeros can be represented by a double colon. This may be done only once in any address. The number of sections removed using this abbreviation can be determined as the number required to bring the address back up to eight sections. For example, 2DAB::DD72:2C4A would need to have five sections of zeroes added back in place of the double colon.


The loopback address


may be abbreviated as ::1.

IPv6 private addresses

Like in IPv4 certain address blocks are reserved for private networks. These addresses are not routed over the public internet. In IPv6, private addresses are called Unique Local Addresses (ULA). Addresses from the FC00:: /7 block are ignored and not routed by default.

Name resolution

In both IPv4 and IPv6, remembering the IP address of every device is not possible, except on the smallest of networks. Name resolution provides a way to lookup an IP address from an easier to use name. 

On the internet, name resolution is handled by the Domain Name System (DNS). With DNS, a name in the format host.domain can be used in place of the destination’s IP address. When the connection is initiated, the source host will request the IP address of the destination host from a DNS server. The DNS server will reply with the destination’s IP address. This IP address will then be used for all communications sent to that name.


quote steffen ille

“The greatest advantage of PRTG? You get to rest easy.“

Steffen Ille, Bauhaus-University of Weimar, Germany


IP Monitoring: 3 handy PRTG features

Auto-discovery quickly identifies IP addresses

PRTG makes it easy for administrators to indicate which IP addresses are relevant. PRTG pings all IP addresses and automatically begins to monitor their associated devices. You will therefore save lots of precious time and can rest assured that everything is covered.

Overview Toplists

By configuring Packet Sniffing or NetFlow sensors, Toplists will automatically be generated in the sensor overview. Toplists contain three categories: top talkers, top connections, and top protocols. These lists enable you to identify the largest bandwidth consumers at a quick glance. You can even create additional Toplists. For more information, see our Toplists page.

250+ sensors make getting started a breeze

PRTG comes with over 250 pre-configured sensors. Among these are sensors for your hardware, bandwidth, website, and server. Check out our sensor list page for details. Sensors make getting started with PRTG - or switching from other monitoring software - both easy and convenient. And in general, setup takes no time at all - even for complex infrastructures. Our Smart Setup scans your network during the installation process and configures some initial monitoring as a starting point. Whether you want to monitor IP addresses or your complete network - PRTG is the tool of your choice.


IP check in PRTG works as follows:


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.



Your IP Monitoring at a glance

PRTG is set up in a matter of minutes and can be used on a wide variety of mobile devices.


PRTG comes with all the features you need, plus more your IT infrastructure won't want to live without.

vendors vm ware


PRTG monitors these vendors and applications, and more, in one view!



With PRTG, you can keep track of IP through automatic packet sniffing.


Trusted by 500,000 users and recognized
by industry analysts as a leader


“Fantastic network and infrastructure monitoring solution that is easy to deploy and easier still to use. Simply the best available.”

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“Software is absolutely perfect, Support is superior. Meets all needs and requirements, this is a must have solution if you are needing any form of monitoring.”

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“The tool excels at its primary focus of being a unified infrastructure management and network monitoring service.”

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IP Monitoring: This is how you scan your traffic with PRTG!


 iAn IP address (internet protocol address) is a numerical representation that uniquely identifies a specific interface on the network. IP addresses are binary numbers but are typically expressed in decimal form (IPv4) or hexadecimal form (IPv6) to make reading and using them easier for humans.
Read more

The starting position

The starting position

As an administrator, you want to keep a close eye on your traffic. And for good reason: one single IP address can use up so much bandwidth that this can ultimately have negative consequences on your entire network. Thanks to PRTG, you will prevent traffic problems over the long term and optimize the performance of your network.


The overview

The overview

How much traffic runs via your network in all? The SNMP Traffic Sensor provides you with a summary of the total amount of traffic which comes in and goes out. Does the Christmas season put added pressure on your online store? Or perhaps marketing campaigns and major updates? With IP Monitoring by PRTG, you can identify weekly, monthly, and seasonal fluctuations. You'll see how traffic develops over longer periods of time, and can promptly take measures to accommodate scenarios such as continual growth.


Fine-tune your monitoring

Fine-tune your monitoring

Your next step is to have a look in greater detail. Via Packet Sniffing, with NetFlow sensors for Cisco devices, or with other flow technologies like sFlow or jFlow, you’ll be able to analyze your traffic more precisely and fine-tune your IP monitoring. The dashboard displays the amount of mail traffic, web traffic, VoIP, file transfers, chat protocols, and much more. Where does such data come from? Who is the recipient? Which protocols are used? This fine-tuning lets you identify bandwidth hogs - whether they be individual users or certain applications or computers together.


PRTG the multi-tool

PRTG: The multi-tool for sysadmins

Adapt PRTG individually and dynamically to your needs and rely on a strong API:

  • HTTP API: Access monitoring data and manipulate monitoring objects via HTTP requests
  • Custom sensors: Create your own PRTG sensors for customized monitoring
  • Custom notifications: Create your own notifications and send action triggers to external systems
  • REST Custom sensor: Monitor almost everything that provides data in XML or JSON format


Looking for an alternative to Nagios? Switch to PRTG!

 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.
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Many users of open source solutions such as Nagios are in search of alternatives to their IP or network monitoring. It is true that the basic versions of open source software are free. But with PRTG, implementation and maintenance are significantly more straightforward, such as can be seen with the configuration of the customizable alarm and notification system. You'll therefore save time and worry - and in the long run, a lot of money. These costs should be taken into consideration when comparing the various tools available.



Open source solutions depend on the support of their communities - and that is a good thing. But when it comes to major problems, administrators need quick and reliable answers so issues can be clearly identified and resolved. Such assistance is provided by the PAESSLER Support Team. Our support team usually answers inquiries within 24 hours. The answers to many questions can already be found in our knowledge base. In addition, numerous videos and web seminars are at your disposal.



One of our greatest priorities is to make our monitoring software intuitive and easy to use. As an administrator, your job should be as stress-free as possible. The user-friendliness of PRTG has been repeatedly proven in countless consumer tests. For more information, read our comparison of Nagios and PRTG here.


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.

IP Fabric

Combining the broad monitoring feature set of PRTG with IP Fabric’s automated network assurance creates a new level of network visibility and reliability.

Read more


By integrating PRTG with Martello iQ, you can add a fast analytics layer to improve uptime, visualize your IT environment, and integrate all of your IT systems into a single pane of glass.

Read more


Rhebo and PRTG offer a comprehensive monitoring solution for IT and OT environments: from condition monitoring through to anomaly and threat detection.

Read more


gerald schoch

Practical tip: “Hey Gerald, what would you tell administrators looking to implement their IP monitoring with PRTG?”

“Those wishing to set up IP monitoring should be ready to go in depth. Our SNMP sensors provide for a quick overview. But our Packet Sniffing and Netflow sensors ensure users get a closer look. Only then is it possible to optimize one’s network on a continual basis.”

Gerald Schoch, Release Manager at Paessler AG


Also interesting:

PRTG monitors the quality of your VoIP-connections. By preventing malfunctions and verifying service level agreements, you’ll save time and money. Read more about IP SLA Monitoring here.

VPN Monitoring: PRTG monitors VPN connections and measures traffic, load, and the number of users. Identify connection problems and suspicious traffic.

Network Security Monitoring: PRTG monitors your firewalls, ports, servers, and much more. Prompt alerts allow you to quickly identify irregularities in your network and maintain the security of your network.


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.



IPv6 Cheat Sheet

You want to know everything about IPv6?

You probably have been working with IPv4 for years. But what about IPv6? In our cheat sheet you get all the details about the IPv6 header, the correct address allocation, typical ICMPv6 error messages and much more.

Get your free copy of our IPv6 cheat sheet now.



Network Monitoring Software - Version (May 24th, 2023)


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


English, German, Spanish, French, Portuguese, Dutch, Russian, Japanese, and Simplified Chinese


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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