Classless Inter Domain Routing Made Easy (Cont..)

Introduction :

As we had a discussion  about Ip addresses and their classes in the previous blog,we can now start with Sub-netting.

Network Mask /Subnet Mask -

As mask means to cover something,

IP Address is made up of two components, One is the network address and the other is the host address.The Ip Address needs to be separated into the network and host address, and this separation of network and host address in done by Subnet Mask.The host part of an IP Address is further divided into subnet and host address if more subnetworks are needed and this can be done by subnetting. It is called as a subnet mask or Network mask as it is used to identify network address of an IP address by performing a bitwise AND operation on the netmask.

Subnet Mask is of 32 Bit and is used to divide the network address and host addresses of an IP.

In a Subnet Mask all the network bits are set to 1’s and all the host bits are set to 0’s.

 

Whenever we see an IP Address - We can easily Identify that

WHAT IS NETWORK PART OF THAT IP

WHAT IS THE HOST PART OF THAT IP

FORMAT :

mmmmmmmm.mmmmmmmm.mmmmmmmm.mmmmmmmm

(Either it will have 1 or 0 Continuously)

EXAMPLE :

A Class Network Mask

In Binary : 11111111.00000000.00000000.00000000         - First 8 Bits will be Fixed
In Decimal : 255.0.0.0

Let the IP Given is - 10.10.10.10

When we try to Identify it we know that it belong to class A, So the subnet mask will be : 255.0.0.0

And the Network Address will be : 10.0.0.0

B Class Network Mask  

In Binary : 11111111.11111111.00000000.00000000           - First 16 Bits will be Fixed

In Decimal : 255.255.0.0

Let the IP Given is -150.150.150.150

When we try to Identify it we know that it belong to class B, So the subnet mask will be : 255.255.0.0

And the Network Address will be : 150.150.0.0

C Class Network Mask  

In Binary : 11111111.111111111.11111111.00000000           - First 32 Bits will be Fixed

In Decimal : 255.255.255.0

Let the IP Given is - 200.10.10.10

When we try to Identify it we know that it belong to class C, So the subnet mask will be : 255.255.255.0

And the Network Address will be : 200.10.10.0

Subnetting :

The method of dividing a network into two or more networks is called subnetting.

A subnetwork, or subnet, is a logically subdivision of an IP network

Subnetting provides Better Security

Smaller collision and Broadcast  Domains

Greater administrative control of each network.

Subnetting - WHY ??

Answer : Shortage of IP Addresses

SOLUTIONS : -

1) SUBNETTING - To divide Bigger network into the smaller networks and to reduce the wastage

2) NAT -  Network Address Translation

3) Classless IP Addressing -

No Bits are reserved for Network and Host

**Now the Problem that came is how to Identify the Class of IP Address :**

Let a IP Be : 10.10.10.10

If we talk about classful we can say it is of class A But in classless : We can check it through subnetwork mask.

255.255.255.0

So by this we can say that first 24 bits are masked for network and the left 8 are for host.

Bits Borrowed from Host and added to Network

Network ID(N)

Network ID(N)

Host ID(H)

Host ID(H)

Network ID(N)

Network ID(N)

Subnet

Host ID(H)

Network ID(N)

Network ID(N)

Subnet

Subnet/Host

Let we have a

150.150.0.0 - Class Identifier/Network Address

150.150.2.4 - Host Address - IP GIVEN TO A HOST

255.255.255.0 - Subnet Mask

150.150.2.0 - Subnet Address

CIDR : Classless Inter Domain Routing

CIDR (Classless Inter-Domain Routing, sometimes called supernetting) is a way to allow more flexible allocation of Internet Protocol addresses than was possible with the original system of IP Address classes. As a result, the number of available Internet addresses was greatly increased, which along with widespread use of network address translation, has significantly extended the useful life of IPv4.

Let a IP be - 200.200.200.200

Network ID(N)

Host ID(H)

--------24 Bit -------- -------8 bit -----------
   

Network Mask tells that the number of 1’s are Masked

Here First 24 Bits are Masked

In Decimal : 255.255.255.0

In Binary : 11111111.11111111.11111111.00000000

   Here the total Number of 1’s : 24

So we can say that 24 Bits are masked.

This method of Writing the network mask can be represented in one more way

And that representation is called as CIDR METHOD/CIDR NOTATION

CIDR  - 200.200.200.200/24

24 : Is the Number of Ones - Or we can say Bits Masked

Basically the method ISP’s(Internet Service Provider)use to  allocate an amount of addresses to a company, a home

EX :

190.10.20.30/28 : Here 28 Bits are Masked that represents the Network and the remaining 4 bits represent the Host

/ - Represents how many bits are turned on (1s)

CLASS C SUBNETTING :

Determining Available Host Address :

<-----------------------NETWORK-----------------------------------><--------HOST----------->

200

10

20

0

11001000               00001010               00010100                 00000000 - 1

                                                                                              00000001 - 2     

                                      00000011 - 3

                                                                          .

                                                                                                    .

                                                                                                    .

                                                                                              11111101 - 254

                                                                                              11111110 - 255

                                                                                              11111111 - 256     

                                                                                                                    -2

                                                                                                               ---------

                                                                                                                   254

    2^N - 2  = 2^8 -2 = 254

           (Coz we have 8 bits in this case)               - 2 (Because 2 Address are Reserved)

254 Address are available here

FORMULAS :

Number of Subnets : ( 2^x ) - 2     (x : Number of Bits Borrowed)

Number of Hosts : ( 2^y ) - 2         (y : Number of Zero’s)

Magic Number or Block Size = Total Number of Address : 256 - Mask

Let a IP ADDRESS BE 200.10.20.20/24

Number of subnets : 5

Network Address   :

200

10

20

20

255

255

255

0

(as total Number of 1’s : 24)

IP in Binary

11001000

00001010

00010100

00010100

MASK

11111111

11111111

11111111

00000000

---

And Operation in IP And Mask

11001000

00001010

00010100

00000000

In Binary

200

10

20

0

As we need 5 Subnets :

2^n -2 => 5

So the value of n = 3 that satisfies the condition

So, We need to turn 3 Zero’s to One’s to create 5 subnets

200

10

20

0

11001000

00001010

00010100

00000000

11001000

00001010

00010100

11100000

 (3 Zero’s changed to 3 one’s)    

200

10

20

224

                                                                                  

Subnet 0   

200

10

20

0/27

Subnet 1                                           +32 - Block Size

200

10

20

32/27

Subnet 2                                            +32

200

10

20

64/27

Subnet 3

200

10

20

96/27

Subnet 4

200

10

20

128/27

Subnet 5   

200

10

20

160/27

Subnet 6

200

10

20

192/27

Subnet 7

200

10

20

224/27

---

How to Put Host ADD.

Subnet 0   

200

10

20

0/27

Subnet Broadcast Number 0

200

10

20

31 /27

Subnet 1                                           +32 - Block Size

200

10

20

31/27

200

10

20

32/27

200

10

20

33/27

                                                          .

                                                          .

                                                          .

200

10

20

62/27

Subnet Broadcast Subnet 1

200

10

20

63/27

200.10.20.33 ….and so on till 200.10.20.62   - 13 Host can be assigned IP Address.

Conclusion :

As the world is growing rapidly towards digitalization, use of IP Addresses is also increasing, So to decrease the wastage of IP Addresses, the implementation of CIDR is important that allows more organizations and users to take advantage of IPV4.