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Subnet Masks & Their Effect

Posted in Subnetting

Introduction

There are a few different ways to approach subnetting and it can get confusing because of the complexity of some subnets and the flexibility they offer. For this reason I created this little paragraph to let you know how we are going to approach and learn subnetting. So.....

We are going to analyse the common subnet masks for each Class, giving detailed examples for most of them and allowing you to "see" how everything is calculated and understand the different effects a subnet mask can have as you change it. Once you have mastered this, you can then go on and create your custom subnet masks using any type of Class.

Internet Protocol Classes - Network & Host ID

Posted in IP Protocol

This article explains the 'Network-ID' and 'Host-ID' concept found in IP addressing and subnetting. We analyse the structure of IP addresses and network classes and show their Network-IDs and Host-IDs in binary format to make evident how the system works.

To help understand the network class analysis, we show examples of well-known ip address ranges and calculate their valid networks and hosts depending on their class and subnetmask.

The information provided in this article is extremely important for engineers who want to really understand IP addressing and subnetting.

Every protocol suite defines some type of addressing that identifies computers and networks. IP Addresses are no exception to this "rule". There are certain values that an IP Address can take and these have been defined by the IEEE committee (as most things).

A simple IP Address is a lot more than just a number. It tells us the network that the workstation is part of and the node ID. If you don't understand what I am talking about, don't let it worry you too much because we are going to analyse everything here :)

IP Address Classes and Structure

When the IEEE committee sat down to sort out the range of numbers that were going to be used by all computers, they came out with 5 different ranges or, as we call them, "Classes" of IP Addresses and when someone applies for IP Addresses they are given a certain range within a specific "Class" depending on the size of their network.

To keep things as simple as possible, let's first have a look at the 5 different Classes:

ip-classes-1

In the above table, you can see the 5 Classes. Our first Class is A and our last is E. The first 3 classes ( A, B and C) are used to identify workstations, routers, switches and other devices whereas the last 2 Classes ( D and E) are reserved for special use.

As you would already know an IP Address consists of 32 Bits, which means it's 4 bytes long. The first octet (first 8 Bits or first byte) of an IP Address is enough for us to determine the Class to which it belongs. And, depending on the Class to which the IP Address belongs, we can determine which portion of the IP Address is the Network ID and which is the Node ID.

For example, if I told you that the first octet of an IP Address is "168" then, using the above table, you would notice that it falls within the 128-191 range, which makes it a Class B IP Address.

The Internet Protocol (IP) Header

Posted in IP Protocol

This article examines the Internet Protocol (IP) and its position within the OSI Model. We take a look at the IP Header and all fields contained within an Ethernet frame. Further examination of the IP header is covered in the next pages that follow.

Binary & The Internet Protocol

Posted in IP Protocol

To understand the Internet Protocol, we need to learn and understand Binary. It is very important to know and understand Binary because part of the IP protocol is also the "Subnetting" section which can only be explained and understood when an IP Address is converted to Binary!

This article deals with the analysis of IP addresses and covers the conversion of IP address to binary. We explain the conversion process with much detail using our well known diagrams. At the end of the article, readers will be able to understand and explain how IP address to binary conversion is performed and also calculate quickly the 32bit addressing scheme.

Those who are experienced in Binary can skim this section quickly, but do have a look through.

A lot of people are not aware that computers do not understand words, pictures and sounds, when we interact with them by playing a game, reading or drawing something on the screen. The truth is that all computers can understand is zeros (0) and ones (1) !

What we see on the screen is just an interpretation of what the computer understands, so the information displayed is useful and meaningful to us. 

Binary: Bits and Bytes

Everyone who uses the Internet would have, at one stage or another, come across the "Byte" or "Bit" term, usually when you're downloading, you get the speed indication in bytes or KBytes per second. We are going to see exactly what a Bit, Byte and KByte is, so you understand the terms.

To put it as simply as possible, a Bit is the smallest unit/value of Binary notation. The same way we say 1 cent is the smallest amount of money you can have , a Bit is the same thing but not in cents or dollars, but in Binary.

A Bit can have only one value, either a one (1) or a zero (0). So If I gave you a value of zero: 0, then you would say that is one Bit. If I gave you two of them: 00, you would say that's two Bits.

Now, if you had 8 zeros or ones together: 0110 1010 (I put a space in between to make it easier for the eyes) you would say that's 8 Bits or, one Byte ! Yes that is correct, 8 Bits are equal to one Byte.

The picture below gives you some examples:

ip-binary-1

It's like saying, if you have 100 cents, that is equal to one Dollar. In the same way, 8 Bits (doesn't matter if they are all 1s or 0s or a mixture of the two) would equal one Byte.

And to sum this all up, 1024 Bytes equal 1 KByte (Kilobyte). Why 1024 and not 1000 ? Well it's because of the way Binary works. If you did the maths, you would find the above correct.

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