IP: definition and types

What is an IP address and what is it used for?

In IT, an IP address is a series of numbers which identify a device known as a host, connected to a network which uses Internet Protocol as its network protocol. This address is linked to an interface which is able to identify the network host to which it is assigned, such as a PC, tablet, smartphone, handheld device, domestic appliance or router; a host can have several interfaces.

In brief, all devices used for browsing the web have an IP address, generally composed of 12 numerical characters (four groups of a maximum of three figures ranging between 0 and 255). In addition, it should be noted that, depending on its characteristics and uses, this address may be private, public, static or dynamic.

Differences between public, dynamic, static and private IP addresses

In order to illustrate the difference between the different kinds of address we should first mention the following point: when any device is connected to the web, it is possible to access the internet via fibre or ADSL in accordance with your ISP (Internet service provider). As soon as the modem requests the connection, an IP address, which is both public and dynamic, is allocated to the device:

• public in the sense that it is assigned uniquely but it is (at least potentially) reachable by any other public IP address (this allows the device to be identified unequivocally and shows the route via which it can be reached by other IP addresses with the same characteristics).
• dynamic in that it is selected from among all IP addresses available by the internet service provider (there is a limited number of IP addresses), supplied and replaced automatically each time the modem establishes a new connection.

A static IP means a public address which is allocated to the same device each time (similar situations arise when devices such as servers need to maintain the same address for long periods).  Considering that addresses are limited in number, as mentioned above, keeping the same one costs a little more.

From the point of view of connection speed, it does not matter whether you possess a dynamic or a static IP address. This individual choice is made according to any specific requirements there may be (an example of this could be the need to make a PC reachable by other nations).

A private IP address, on the other hand, is one that your own device obtains from the router when it is connected to any LAN network. It is only used by the router to which the devices of that LAN are connected; the router recognises them and enables all the necessary data to be processed.

This type of address can be set manually or it can be assigned by the router as soon as a device connects to the network (we should point out that all routers know which route the data must follow to enter or exit the device, thanks to what are known as routing tables).

That concludes our brief overview of the definition of an IP address and its four variants (private, public, static or dynamic):  the numerical 32-bit code, usually composed of four complete numbers divided by dots, which allows the identification of a device connected to the web.

Translated by Joanne Beckwith