Get into cybersecurity with no experience, Lesson 5- What is a network, Internet, MAC address, VPN, IP addresses and its different types.

In the previous article, we looked at “what is penetration testing and its many sorts and classifications.” In this blog, we’ll look at how the internet actually works now that we’ve covered all of the fundamental theory.

So without further delay, let’s get started.

What is a network?

When two or more devices are interconnected to each other, they form a network.

What is internet, you ask?

Networks of Network. (It’s that simple, however most people do not give a second thought about how the internet works)

for example- Consider the following scenario: House A has a WiFi connection to which all of its mobile phones, laptops, computers, and other electronic devices are linked. Let me ask you a question: is it a network or the internet?
It is, in fact, a network. Similarly consider House B, which has its own WiFi network and to which all of its equipment and appliances are connected (This is also a network). So when House A & House B are connected to each other, they form the internet. (Wow, see how simple it is; we used to think it was too difficult to learn in 7th or 8th grade; now there’s nothing to learn if you just comprehend).
Take a look at the graphic below for a better understanding.

Consider the following scenario: A1 wishes to transmit some data or a message to A2, but we can’t simply say, “A1 send data to A2,” because machines are unfamiliar with these command. Since all these computers and servers are interconnected together, there needs to be a way for them to know where to send the requests and data. This is when protocol comes in handy.

What is an IP address?

The Internet Protocol (IP) stands for “the collection of rules defining the format of data transferred over the internet or other network.” It is the cornerstone of how the internet operates and how different systems connect with one another in layman’s words.

On basis of its nature it is divided into two categories:-

  1. Public IP Address
  2. Private IP Address

On basis of its version and capacity:-

  1. IPV4
  2. IPV6
  • Another address unique to each & every device is known as MAC Address(Media Access Control).
  • Any device that can be connected to a network or internet will have IP & MAC Address.
  • Each machine on an ideal condition will have two IP Addresses:- Public IP &Private IP.

Private IP Address- In a network, the unique IP Address is known as Private IP address. It may or may not be unique in the internet.

Private IP Address- Private IP address is unique in the internet. It is not unique in the network.

Got confused? Here’s an example for your better understanding.

Example- Your cell number is unique within the country (here, a country is a network, and the globe is the internet (a collection of interconnected countries), but it may or may not be unique globally. Now (+91, country code) is a one-of-a-kind number in the world, yet it is widely used in the country. So, in this case, the mobile number represents a private IP address, whereas (+91) represents a public IP address.
Reread those definitions; you should now comprehend them.

We will here only talk about IPV4 since IPV6 isn’t common yet.


  • It is 32 bit.
  • a.b.c.d — each character is known as octet.
  • the max value an octet can hold is 256, i.e. 0–255 and the minimum value it can hold is 0.

In Private IP Address, first two octet has to be 192.168 and the rest two can be any in the given limit.

  • so max-
  • and min-
  • here first three octet are network part and the last octet is host part.

DHCP(Dynamic host configuration protocol)- Assigns Private IP Address to the machines.

Public IP Addresses are dynamic & are provided by ISP(Internet service provider).

  • Public IP address can be any except it cannot start with 192.168 or 10.10

Hmm, we get it that Public IP cannot start with 192.168(since Private IP starts with it) but why 10.10?

  • Consider the following scenario: Network A and Network B are not interconnected, or are in separate towns or countries, but A1 still wishes to exchange data or communicate with A2. In this instance, they can connect through a VPN (Virtual Private Network) and are assigned an IP address that begins with 10.10. As a result, public IP addresses cannot begin with 10.10.

So this brings our today’s blog to an end.

Hope you understand and like this blog.

The next blog will be on “What are ports, Default gateway, web server, DNS and what are the types of protocols and difference between them.” and it will be out on 09/06/2021.

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Chitranjan is an Ethical Hacker with hands-on experience in network, android and web peneteration testing.