What are IP addresses?

binary numbers in front of mobile devices

While choosing your server you will find in the specs the amount of IP addresses you will get with your plan. If you just started you might wonder what are IP addresses? What do they do, what are they good for? Well IP addresses are basically addresses for your devices on the IP network.

IP stands for Internet Protocol and it is responsible for addressing hosts, encapsulating your data into datagrams and routing these datagrams over the network from the source to the destination. IPv4 is the fourth and most spread version of the IP protocol. The successor for IPv4 is IPv6, which became needed after the quick address exhaustion of IPv4.


Ipv4 uses a 32-bit addressing system, what limits the address space to 4,294,967,296 (232) addresses. IPv4 addresses may be represented in any notation expressing a 32-bit integer value. They are most often written in the dot-decimal notation, which consists of four octets of the address expressed individually in decimal numbers and separated by periods. For example: what is most likely the address for you home router.

The addresses are organized into classes, which is decided by the first octet of the IP address. The classes are: Class A, B, C, D and E. In Class A the first bit of the address is always ‘0’, so it ranges from 1.x.x.x to 126.x.x.x . The default subnet mask for Class A is, what means that the first three octet identifies the network and the last identifies the host. So in Class A you can have 126 networks and 16777214 hosts.

In Class B the firs two bits of the first octet is always ’10’. Class B IP Addresses range from 128.0.x.x to 191.255.x.x and the default subnet mask for Class B is 255.255.x.x. You can have 16384 host addresses and 65534 host addresses in Class B.

Class C is defined by the first 3 bits set to 110, so it ranges from 192.0.0.x to 223.255.255.x . The default subnet mask is 255.255.255.x so Class C gives 2097152 Network addresses and 254 Host addresses.

In Class D the first four bits are set to ‘11110’, so it range from to . Class D is reserved to multicasting and have no subnet mask. Class E is reserved for experimental and R&D purposes, and doesn’t have subnet mask either.


Since the definition of IPv4 in the 1980’s it became clear that the available IPv4 addresses deplete much faster that it was anticipated. To provide a long term solution to this problem a new definition was introduced in the 1990’s. IPv6 addresses are 128 bit addresses and are represented in 8 groups of 16 bits each.

They are written in hexadecimal digits, and each group is separated using a colon like 1234:5678:0000:0000:0000:0000:abcd:00ef . IPv6 addresses  can be shortened for convenient use. Leading zeroes within a group can be removed (002e -> 2e) and consecutive groups of zeroes can be replaced with a double colon. If we take the previous address for example, it can be shortened to 1234:5678::abcd:ef .

Additional to the extended address range the packet header and the processing of the header was simplified. This allows packets to travel faster over network and also takes off processing from the router devices. There are a lot more useful features of the IPv6 that makes them more secure and faster to arrive to the destination.

What are IP addresses used for? They are representing a device on the network that you can reach. So if you want to send something to a device you can send it to it’s address. Every device and website are reached through IP addresses, but you usually use domain names for that. Domain Name System replaces the IP address, so the target destination can be more easy to remember.


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