What is an IP address?

In order to receive regular mail, the postal service in your country has to know where to deliver your mail. Well, on the internet it works kind of the same way. You either have an IPv4 or an IPv6 address

Public vs Private

Simply put 😉 a public IP (address) is the address that everybody knows and is supposed to know, because it is, … public right? This means that even a computer at the other side of world knows has a way to get to your public IP. These public IPs you can buy at your service provider and they will announce to the world that you have bought this/these IP addresses.

Private IPs are as the name implies private to your network. This means that this same machine at the other end of the world does not know how to get to your private IP address.

Why this difference?

In theory we could have assigned a public IP to any computer in the world and this design would work … but for a short while though. The IP space of IPv4 addresses as most of you know them (e.g. 12.123.44.55) has only 4 294 967 296 (2 to the 32 power, or 4 times 8 bites) IP addresses available.

So the community thought about a medium term solution and divided this total of 4 billion IP address into public address and private addresses. The private address ranges are the following:

• 10.0.0.0/8
• 172.16.0.0/12
• 192.16.0.0/16

These ranges were agreed on to be never used on the public side of networks.

Is this a solution for the exhausted IPv4 range?

Yes and no. We won some time. What people could do now is assign a private IPv4 address to all hosts within their network and limit the use of public IPs. For example: hosts that wanted to connect to something on the internet, could do so using 1 public IP per roughly 65000 users.

Let’s be honest: it bought and is still buying us in some parts of the world a huge amount of time. But it was not a long term plan.

IPv5 then … no IPv6

The more long term solution came with IPv6. IPv6 addresses consist of 128 bits meaning it can 2¹²⁸ or 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses

To delve into all the different types of IPv4 and IPv6 address would lead us to far for now.

But as always, there will be another article if requested in the comments.