IP Address

Everyone knows that for a letter to reach the right recipient, you need to provide the exact address, including country, city, ZIP code, street and house number. Only then do the post office and its staff know where to send it. The same is true on the internet: every device within an internal or external network needs a unique “house number” to com­mu­ni­cate with other devices and receive data packets from them. But an IP address looks com­plete­ly different from the address you write on an envelope. Read on to learn more about these cryptic digits.

The internet protocol address (also known as the “IP address” or simply the “IP”) is based on the internet protocol that is also the un­der­ly­ing foun­da­tion of the internet. It refers to the uniquely iden­ti­fi­able address of a device (such as a computer, web server or printer) in an internal or external network. An IP address can also designate a whole group of devices, as is the case with broad­cast­ing or mul­ti­cas­t­ing. Likewise, a single computer could be assigned multiple addresses. However, each IP address in a network can only be used once at any given time.

There are two versions of IP addresses which look very different. What they have in common is that they contain a network component (for IP routing) and a device component (for as­sign­ment to a certain computer).

At the moment, addresses following Internet Protocol Version 4 (IPv4) are pre­dom­i­nant­ly in use. They consist of 32 bits and tech­ni­cal­ly therefore refer to a 32-digit binary number, such as 11000000 10101000 10110010 00011111. To keep this numerical beast under control, it’s typically rep­re­sent­ed as a com­bi­na­tion of four decimal figures with values from 0 to 255, separated by points. In this format, our example looks like this: 192.168.178.31.

IPv4 is able to con­sti­tute around 4.3 billion different addresses in total. Although this is far less than the number of devices in the world (and many of them are reserved for special ap­pli­ca­tions), all of them are never required si­mul­ta­ne­ous­ly and some are only used in private networks. For this reason, this number has been quite suf­fi­cient so far.

However, this fact will soon change, not least due to the Internet of Things (IoT): As more and more everyday devices are able to connect to the internet and a large share of them need their own IP address, the avail­abil­i­ty of IPv4 addresses is gradually becoming scarce. To this end, IPv6 has been launched as the direct successor, enabling around 340 un­decil­lion (a number with 37 zeros) addresses – an almost in­ex­haustible supply for all future IP re­quire­ments.

Addresses of this version have 128 bits and would therefore have to be written as a 128-digit binary number. Since such a number is far too long and im­prac­ti­cal, hexa­dec­i­mal notation is applied to compress the 128 bits into eight blocks of 16 bits, separated by colons. This results in the IPv6 address of 0000:0000:0000:0000:0000:ffff:c0a8:b21f, for example. Here, the letters a to f are also used as hex digits. If we omit the zeros at the start of every block and replace a series of con­sec­u­tive 0000-blocks with two colons (::), this format can be sim­pli­fied even further. In our example, this would produce the following shorthand: ::ffff:c0a8:b21f.

An IP address enables the clear iden­ti­fi­ca­tion and ad­dress­ing of a device in an internal or external network. It therefore provides the basis for trans­port­ing in­for­ma­tion from the sender to the right recipient. If a device wants to send a data packet, the as­so­ci­at­ed router orients itself on the IP header and rec­on­ciles the source IP with the target IP. If both network com­po­nents match, the sender and recipient are located within the same network and the packet is sent directly.

If this is not the case, the router (the internet’s post office) contacts the global Domain Name System (DNS). This system is re­spon­si­ble for name res­o­lu­tion online, i.e. for trans­lat­ing device names into IP addresses and vice versa. For instance, when accessing a website , the DNS provides the IP as­so­ci­at­ed with the URL: The domain www.example.com is converted to the IPv4 address 93.184.216.34 or the IPv6 address 2606:2800:220:1:248:1893:25c8:1946, for example. The data packet is then forwarded to the recipient’s router via multiple routers, networks and subnets.

The highest body for assigning IP addresses is the Internet Assigned Numbers Authority (IANA), which in turn is a de­part­ment of the Internet Cor­po­ra­tion for Assigned Names and Numbers (ICANN). It has complete control over the entire avail­abil­i­ty of IP addresses and assigns blocks of them to five Regional Internet Reg­istries (RIR), namely AfriNIC, APNIC, ARIN, LACNIC and RIPE NCC (short for: Réseaux IP Européens Network Co­or­di­na­tion Centre).

The latter is re­spon­si­ble for Central Asia, the Middle East and Europe (hence also Germany) and allocates its assigned IP addresses to Local Internet Reg­istries (LIRs) and National Internet Reg­istries (NIRs). They sub­se­quent­ly pass on IP addresses to (sub)providers or directly to end customers.

A dis­tinc­tion is typically made between dynamic and static IP addresses. There are also IP addresses “for special purposes” – most of which are reserved for private networks.

Dynamic IP addresses are most fre­quent­ly used for normal online browsing. When a DSL customer dials into the internet using their router, their internet service provider (ISP) assigns them with an un­al­lo­cat­ed, random IP address. This as­sign­ment is deleted again after each session or is au­to­mat­i­cal­ly changed at regular intervals, usually every 24 hours.

Since each available IP address can be “reused” in this way, the provider needs far fewer addresses than it has customers – after all, they’re never all online at the same time. Together with IPv6, dynamic addresses therefore help to mitigate the scarcity of the IPv4 address space. Since they’re also less expensive than static addresses, this results in a cost advantage for the provider who’s able to serve more customers with a smaller pool of addresses.

Moreover, they benefit from privacy pro­tec­tion with respect to third parties, as dynamic IP addresses enable users to surf more anony­mous­ly. Con­verse­ly, website operators lose out, as a con­stant­ly changing IP address is un­suit­able for tracking visitor behavior. Instead, cookies are generated then deleted again after a certain period of time. Only the internet service provider is able to track what its customers are doing based on their IP. However, this has been the subject of data pro­tec­tion disputes for quite some time, par­tic­u­lar­ly con­cern­ing telecom­mu­ni­ca­tions data retention.

A static IP address always remains the same, unless the owner actively changes it them­selves. These IP addresses are used for web servers, for example, which always have to be ac­ces­si­ble at the same URL. They are also employed in private networks (LANs) for com­mu­ni­cat­ing with a local printer or another computer in a home network. From a user per­spec­tive, the biggest dis­ad­van­tage of static IP addresses compared to dynamic addresses is that they are far easier to track.

The IANA has reserved around 14.5 percent of the IPv4 address space for special purposes. Here are a few examples:

• The IPv4 address space 0.0.0.0 to 0.255.255.255 – en­cap­su­lat­ed in the CIDR address block 0.0.0.0/8 – refers to the host of a network.
• When the IP address 127.0.0.1 is dialed, it’s possible to com­mu­ni­cate with the local host, i.e. the user’s own computer. This is necessary for testing newly pro­grammed ap­pli­ca­tions, for instance.
• The IP address 255.255.255.255 is des­ig­nat­ed for broad­cast­ing.
• The address spaces 10.0.0.0 to 10.255.255.255, 172.16.0.0 to 172.31.255.255, and 192.168.0.0 to 192.168.255.255 are reserved for private networks in which they can be used without any reg­is­tra­tion. In the case of IPv6, the prefix fc00::/7 is des­ig­nat­ed for private use.

These IPs are not assigned by the IANA and also don’t route to the internet. But if you do want to go online, the router converts the private IP address into a valid IPv4 or IPv6 address ap­plic­a­ble to all devices in the local network by means of network address trans­la­tion (NAT). For incoming data packets, this process is reversed. Admins can dis­trib­ute private IP addresses either manually or au­to­mat­i­cal­ly via the DHCP server.

Although IP addresses them­selves do not contain any in­for­ma­tion, they can be used to draw con­clu­sions on the user. As a result, they are the subject of dispute among data privacy advocates.

First of all, it’s rel­a­tive­ly easy to link a user’s IP address to their internet provider. For example, if it begins with the numbers 81, 91 or 212, the address belongs to Deutsche Telekom. This can simply be de­ter­mined by means of a reverse DNS query or the command line tool Tracert. Other numbers indicate certain companies or agencies, if you know which address spaces are assigned to them by the re­spon­si­ble LIRs or NIRs.

Depending on how close the user of an IP is to the next internet dial-in node, an exact location may be iden­ti­fi­able to some extent. In rural areas, it’s only possible to ascertain a general area. But in urban areas, “ge­olo­ca­tion” is much more precise since dial-in nodes can be found here almost every few hundred feet.

The short answer: Yes. IP addresses es­sen­tial­ly enable internet providers to monitor and track their customers’ stream of data. This means storing IP addresses is a con­tro­ver­sial issue. After all, the General Data Pro­tec­tion Reg­u­la­tion (GDPR) has de­ter­mined that IP addresses, re­gard­less of whether they’re dynamic or static, fall into the category of personal or per­son­al­ly iden­ti­fi­able data as online iden­ti­fiers and as such require special pro­tec­tion.

This results in strict rules for handling data pro­tec­tion, such as in e-commerce. For instance, website operators may only store a user’s IP address if this is ab­solute­ly necessary for the purpose and func­tion­al­i­ty of their range of products or services. Only security agencies are permitted special access rights in criminal matters.

It’s im­pos­si­ble to fully hide an IP address, but it can be ob­fus­cat­ed in a number of ways. Here, the basic principle is always the same: Data packets are first redi­rect­ed to a server that has its own IP address and then forwarded to the recipient. The following tools are available for this purpose:

• The Tor Browser Bundle, based on Mozilla Firefox, enables users to browse the internet anony­mous­ly. Since all data packets first have to pass through a separate network, high band­widths aren’t possible at times.
• Virtual private networks (VPNs) allow the encrypted trans­mis­sion of data. When you browse the web via a VPN, the requested web server only sees the IP address used by the VPN and not the user’s own address.
• A proxy server can also accept data packets and forward them through its own IP address.

If you want to configure an email program or a cloud service, it’s sometimes necessary to enter your IP address manually. But where can you find it?

The standard tools available to an operating system are suf­fi­cient to display a computer’s local IP:

• For Windows, all you have to do is enter the command “ipconfig” into the input prompt. This can be opened by pressing the [Windows] + [R] keys and entering “cmd” into the console that appears.
• The local IP of a Mac computer can be viewed as follows: System settings > Network.