Tag: Subnet Mask

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 :
 
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.