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
——–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 :
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 :
(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
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
|
11001000
|
00001010
|
00010100
|
00000000
|
|
11001000
|
00001010
|
00010100
|
11100000
|
(3 Zero’s changed to 3 one’s)
Subnet 0
Subnet 1 +32 – Block Size
Subnet 2 +32
Subnet 3
Subnet 4
Subnet 5
Subnet 6
Subnet 7
How to Put Host ADD.
Subnet 0
Subnet Broadcast Number 0
Subnet 1 +32 – Block Size
.
.
.
Subnet Broadcast Subnet 1
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.
