In home networks, IP addresses are almost never fixed, but vary within specific ranges. It is the router that assigns a new IP address automatically when the computer connects to the network or if there are changes to the configuration.
To the user, the fact of having an IP or another does not change anything in the speed of the internet and in the functionality of the applications.
When we talk about static IP instead we want that network address never to change.
In this case it is the computer that decides the address it wants, communicating it to the router.
The question then is as follows: why internet providers ask for the payment of an additional fee if you want a Static IP and for what reason one should want it, what are the advantages "> You have to imagine the internet world as a set of routers and computers that are identified by specific IP addresses, but that create many internal subnets to which thousands of computers can be connected, each with a different address only within this private network, which, however, all flow into the same single external IP address.
This also applies if you only have one computer on your home network; it will have a private IP assigned by the router.
Private IP addresses cannot be routed over the Internet and are always the same in every network in the world: 192.168. *. * (where * can be anything) or 10.10.xx.
For example, the interface of most routers around the world are accessible only from computers within the network, via the IP address 192.168.0.1.
The computers connected to these routers have internal IP addresses that have values within a range from 192.168.0.2 to 192.168.0.254.
The first computer that connects to the router, via the DHCP service, sends a network request saying: "I need an IP address, my hardware address is xxxxxx" and is assigned 192.168.0.2, the next one will have 192.168.0.3 and so on.
However, all these PCs come out on the internet with a shared IP address, different from the private one, assigned to the router (which acts as the central point of a network) by the internet provider.
In networks like Fastweb, your home router is inside another private subnet so the external IP becomes shared even among hundreds of computers located in different areas of the city.
When we talk about setting a fixed IP on the computer, we are talking about keeping the same private IP assigned, in order to impose a specific address on the router, which never changes.
In large offices, instead of randomly assigning IP addresses to computers, you set these addresses directly in the router.
An association is made between the hardware addresses of the pc (MAC Address) with the internal IP addresses so a given computer always has the same.
However, this does not change the public IP, the external one that comes out on the internet.
The external IP address is not something that can be changed and is automatically given by the Internet provider.
However, it is possible to purchase an external static IP address, but it is absolutely not convenient because they are expensive and because there are methods to obtain the same advantages even without them.
The advantage of having an external static IP address is that of being able to reach your computer from anywhere in the world via the Internet .
Essentially, a static IP is used to transmit packets via the Internet to certain computers or devices on the home network.
For example, this is useful if you want to create a local Web server (creating a website that resides on your PC), for an FTP server (to make the files saved on your PC available from anywhere) to configure a radio that transmits computer music via the internet or to create a remote surveillance system, to keep an eye on the webcam footage.
To configure a web server in your home network to be accessible by anyone worldwide, you need to forward incoming requests on port 80 for the web server machine.
It is therefore obvious that if the web server gets a new IP from the router every time, this cannot work.
Thanks to technology, however, it is possible to do the same things even without purchasing the external static IP
If you need to access the home network from a remote location (translated: connect to your home PC via the internet), there are services that automatically update the dynamic IP address assigned by the router when it changes .
If you configure an internal static IP you can also associate it with an external IP (for example through the free service of No-ip.com).
In practice, an association is made between your computer and an external online service that acts as a link and allows you to bypass the rules of the router.
This has been explained, in different terms, in two guides:
- Create a server on your computer to share resources on the internet
- Connect to your home PC from anywhere with dynamic DNS.
There is also the technique of port forwarding on the router that allows you to connect to a computer program remotely.
To know your internal IP address, just open a command prompt (from the Start menu -> Programs -> Accessories) and write the IPConfig command.
To know your external dynamic IP instead you can use an online service like My IP mentioned in the post on "how to find the IP address of another computer and locate it".
