We need to have the basic knowledge of Networking concepts like IP Addresses, Subnets, and CIDR Notation before working on any Cloud infrastructure. Here I am giving the basic and to the my knowledge on few important concept like CIDR notation, Subnet Mask, Subnetting which will be useful for any cloud vendors

Table of Contents

## What is IP Address

- IP addresses are nothing but 32 bits long– IPv4– and these are four octets of 8 bits each

Example11111111.1111111.11111111.11111111 Which is read in decimal form as 255.255.255.255

- An IP address is interpreted as composed of two parts: a network-identifying prefix followed by a host identifier within that network.
- IP address consists of two groups of bits in the address: the most significant bits are the network prefix, which identifies a whole network or subnet, and the least significant set forms the host identifier, which specifies a particular interface of a host on that network. This division is used as the basis of traffic routing between IP networks and for address allocation policies.
- Earlier address was considered to be the combination of an 8, 16, or 24-bit network prefix along with a 24, 16, or 8-bit host identifier respectively. And this was called Class-full Network routing
- Class A networks, which all 8 bits– the first octet being all 1’s. Class B network which is the first two octets being all 1’s, and class C network which is the first three octets all 1’s.
- Before moving further ,lets find out how to convert IP address from binary to decimal and decimal to binary

## Binary to Decimal conversion and Vice Versa

### Binary to Number conversion

Lets take an example where all the 32 bits are 1

11111111.1111111.11111111.11111111

We can convert to Number for each octet using the formula given below

2^{7}x 1 + 2^{6}x1 + 2^{5}x 1 + 2^{4}x1 + 2^{3}X 1 + 2^{2}x1 + 2^{1}x 1 + 2^{0}x 1=128 + 64 + 32 + 16 + 8 + 4 +2 +1=255

So each bit is multiplied by power of 2 corresponding to there position

So, calculating the same way, we get

255.255.255.255

**Another example**

11000000 – 10101000 – 00000000 – 00000101

*First Octet*

11000000

=2^{7}x 1 + 2^{6}x1 + 2^{5}x 0 + 2^{4}x0 + 2^{3}X 0 + 2^{2}x0 + 2^{1}x 0 + 2^{0}x 0

=128 + 64= 192

*Second Octet*

10101000 =2^{7}x 1 + 2^{6}x0 + 2^{5}x 1 + 2^{4}x0 + 2^{3}X 1 + 2^{2}x0 + 2^{1}x 0 + 2^{0}x 0=128 + 32 + 8= 168

*Third Octet*

00000000 =2^{7}x 0 + 2^{6}x0 + 2^{5}x 0 + 2^{4}x0 + 2^{3}X 0 + 2^{2}x0 + 2^{1}x 0 + 2^{0}x 0=0

*Fourth Octet*

00000101 =2^{7}x 0 + 2^{6}x0 + 2^{5}x 0 + 2^{4}x0 + 2^{3}X 0 + 2^{2}x1 + 2^{1}x 0 + 2^{0}x 1=4 + 1 =5

So, Decimal IP address is 192.168.0.5

**Binary to Decimal Conversion**

1. We can get binary number by continually divide-by-2 (two) to give a result and a remainder of either a “1” or a “0” until the final result equals zero.

2. Then we write the remainder from bottom

3. If the count of remainder is less than 8 ,we add the zero to the left of the binary number

**Example****192.168.0.5**

*First take for 192*

So, Binary number is 11000000

*Now take for 168*

So, 10101000

*Now take 0*

this will be 0 only So, we can write 00000000

*Now take 5*

So, binary is 101

Now since count is less than 8, we can add zero padding at the left end

00000101

So Binary equivalent is**11000000 – 10101000 – 00000000 – 00000101**

## What is Subnet mask or netmask?

- A subnet mask separates the IP address into the network and host addresses. The whole idea of network and host is actually done using subnet masks.
- Subnet mask is made by setting network bits to all 1’s and setting the host bits to all 0’s
- It uses the same format as an IPv4 address — four sections of one to three numbers, separated by dots

**Example**

192.168.0.5

If this is class C address and 24 bit is the network address, then subnet mask will be

11111111.11111111.11111111.00000000

Converting to Decimals

255.255.255.0

So, this is the subnet mask for this IP address

## Classless Inter-Domain Routing ( CIDR)

- Earlier Classful network design has some flaws like wastage of IP addresses, Classless Inter-Domain Routing ( CIDR) was introduced to resolved it.
- Classless Inter-Domain is a method for allocating IP addresses and IP routing
- Unlike classful network design where network prefix as one or more 8-bit groups, resulting in the blocks of Class A, B, or C addresses, CIDR address allows any address-bit boundary
- it introduced a new method of representation for IP addresses known as
**CIDR notation**, in which an address or routing prefix is written with a suffix indicating the number of bits of the prefix, such as 192.168.0.5/24 or 192.168.0.5/26 - So, in first 24 bit are for Network and in second 26 bit is for the Network. We can convert this to subnet also

(1) 192.168.0.5/24 Subnet Mask will be 11111111.11111111.11111111.00000000 Converting to Decimals 255.255.255.0 (2) 192.168.0.5/26 11111111.11111111.11111111.11000000 Converting to Decimals 255.255.255.192

If we need to tell the network prefix of this address, we can use the below method

Let’s understood with the example 192.168.0.5/26 (1) Convert the IP into binary format 11000000 - 10101000 - 00000000 - 00000101 (2) Write the 1’s bit below as given for the network 11111111.11111111.11111111.11000000 (3) Write them together as below 11000000 - 10101000 - 00000000 - 00000101 11111111 – 11111111 - 11111111 - 10000000 (3) Do logical add on above and below for each bit 1100000-10101000-00000000-00000000 Which can be written in decimal As 192.168.0.0 So, this is network prefix

## Subnetting

- Subnetting is the process of dividing large network into smaller network.
- Basically, it is designating some high-order bits from the host part as part of the network prefix and adjusting the subnet mask appropriately

For the network 192.168.0.0/24 , the last eight bit is used for host. So total number host possible is

28 = 256.

We can divide this network into many subnets

The number of networks formed depends on the bit taken

- If 1 bit is taken . Two networks are formed as that bit can be 0 or 1 i.e. 2
- If 2 bits are taken , four networks are formed, as 01,10,11,00 is the possible combination
- If 3 bit are taken , 8 network are formed, as 001,100,111,000,101,010,110,011 is the possible combination

Hosts in each will be define by the number of bit remaining for Host portion

- So, for 25-bit, host will be 2^7 = 12
- So, for 26-bit, host will be 2^6 = 64
- So, for 27-bit, host will be 2^5 = 32

The network Prefix for each of these networks can be

- If 1 bit is taken . Two networks are formed as that bit can be 0 or 1 i.e. 2. Network Prefix will be 192.168.0.0 and 192.168.0.128
- If 2 bits are taken , four networks are formed, as 01,10,11,00 is the possible combination,Network Prefix will be 192.168.0.0 ,192.168.0.64, 192.168.0.128, and 192.168.0.192
- If 3 bit are taken , 8 network are formed, as 001,100,111,000,101,010,110,011 is the possible combination,Network Prefix will be 192.168.0.0 ,192.168.0.32, 192.168.0.64, 192.168.0.96,192.168.0.128,192.168.0.160, 192.168.0.192 and 192.168.0.224

I hope you find this information on IP Addresses, Subnets, and CIDR Notation. This is going to helpful when working with Oracle cloud Infrastructure

**Related Articles**

oracle cloud infrastructure : Oracle Infrastructure as a Service is called Oracle Cloud Infrastructure (OCI).It offers storage,compute ,database, networking, edge services

OCI block storage : OCI Block storage is the NVMe SSD based storage that you can attach to any compute instance that was launched. Check out about backup,cloning

Local NVMe storage in OCI :Local NVMe storage is a SSD based temporary storage. Check out details about Local NVMe storage in OCI and how to use it in Oracle cloud

Virtualization : Virtualization is the process of creating multiple virtual machines /operating system from one physical hardware box with the help of hypervisor

what is cloud computing : Learn about what is cloud computing and how it can benefit organization. Various cloud model ,cloud vendors ,cloud examples

iaas paas saas : Learn about Cloud Computing Basics: iaas paas saas with offerings

https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing

## Recommended Courses

Cloud Computing Concepts : it Covers Fundamentals of Cloud Computing and types of cloud like private, public, hybrid, IAAS, SAAS, PAAS and cloud platforms like AWS, Azure and Google Cloud.One of must have course for anybody starting with Cloud

Introduction to Cloud Computing on Amazon AWS for Beginners : Learn about Amazon Web services.Various offering available with it like EC2, EBS ,S3. A good course for anybody starting with AWS

Google Cloud Platform (GCP) Fundamentals for Beginners : Learn how to use GCP compute, storage, and networking services, Key services of Google Cloud Platform.A good course for anybody starting with GCP

Introduction to Cloud Security with Microsoft Azure : It covers Azure services, Azure PowerShell . A good course for anybody starting with Microsoft Azure

## Leave a Reply