This document discusses subnetting and CIDR notation. Subnetting allows a single address block to be divided into multiple networks or subnets. It maximizes address efficiency, extends the life of IPv4 addresses, and makes networks easier to manage. CIDR notation uses a slash to indicate the number of network address bits. The document provides examples of how to calculate the number of subnets, valid host addresses, and network vs broadcast addresses using CIDR and a subnet mask. It also defines what a subnet mask is - a 32-bit address that distinguishes the network from host portions of an IP address.

1. Mohammad Junayed Khan
Noor
163002029
Subnetting

2. WHAT IS
SUBNETTING?
Allows Creating multiple network from a
single address block.
Subnetting is a process of breaking large network
in small networks known as subnets.

3. WHY
SUBNETTING?
Maximise addressing efficiency.
Extend the life of IPV4.
Public IPV4 Addresses are scare.
Easy to manage.
Subnetting reduces network traffic by removing
collision and broadcast traffic, that overall
improve performance.
Subnetting allows you to apply network security
polices at the interconnection between subnets

4. CIDR [ Classless Inter Domain Routing]
CIDR is a slash notation of subnet mask. CIDR
tells us number of on bits in a network address
CIDR Decimal Binary
/25 128 10000000
/26 192 11000000
/27 224 11100000
/28 240 11110000
/29 248 11111000
/30 252 11111100

5. FORMULAS &
VARIABLES
h=number of host bits
n=number of host bit use in network bits
Number of new networks reulting from the
subnetting: =2^n
Number of hosts per new network: =2^h-2
One is network another is broadcast
Broadcast address is the last address of subnet.
Block size or increment number is used to calculate the valid
subnets

6. EXAMPLE:-
Subnet base address
New CIDR length /25
255.255.255.128(Subnet Mask)
h = 7 [Remaining host bits]
192 168 1 0/24
11111111 11111111 11111111 00000000
N N N H
192 168 1 0/25
11111111 11111111 11111111 10000000

7. EXAMPLE:-
1*192.168.1.0/25
Valid subnets 0,128
Valid host per subnets (2^h-2)=2^7-2=126
Subnets Subnet 1 Subnet 2
Network ID 192.168.1.0 192.168.1.128
First host 192.168.1.1 192.168.1.129
Last host 192.168.1.126 192.168.1.254
Broadcast ID 192.168.1.127 192.168.1.255

8. EXAMPLE:-2
If mask is 26
Total hosts (2h) :- 26 = 64
Valid hosts per subnet ( 2^h- 2 ) :-
64 - 2 = 62
Subnets Subnet 1 Subnet 2 Subnet 3 Subnet 4
Network ID 0 64 128 192
First host 1 65 129 193
Last host 62 126 190 254
Broadcast ID 63 127 191 255

9. SUBNET
MASK
• Subnet mask is a 32 bits long address used to
distinguish between network address and host
address in IP address. Subnet mask is always used
with IP address. Subnet mask has only one purpose,
to identify which part of an IP address is network
address and which part is host address.

10. 1ST IP
• A block of addresses is granted to a small organization. We
know that one of the addresses is 205.16.37.39/28. What is
the first address in the block?
• Solution
• The binary representation of the given address is
• 11001101 00010000 00100101 00100111
• If we set 32−28 rightmost bits to 0, we get
• 11001101 00010000 00100101 0010000

11. THANK YOU