Azure Classroom Series – 19/Mar/2021

Networking Basics contd

• Lets try to revisit cidr notations

192.168.0.0/16

sm: 11111111.11111111.00000000.00000000
sm: 255.255.0.0
size of network => number of 0's => 2^16-2 =>65536-2 => 65534

172.16.0.0/21
sm: 11111111.11111111.11111000.00000000
sm: 255.255.248.0
size of network => number of 0's => 2^11-2 => 2048 -2 => 2046 devices

10.10.0.0/18
sm:11111111.11111111.11000000.00000000
sm:255.255.192.0
size of network: number of zeros => (32-18) => 14 => 2^14-2 => 16384-2 => 16382

• There are some cidr ranges reserved for private networking.
  • 10.0.0.0/8 => 10.0.0.0 – 10.255.255.255
  • 192.168.0.0/16 => 192.168.0.0 – 192.168.255.255
  • 172.16.0.0/12 => 172.16.0.0 – 172.31.255.255
• Scenario-1: we want to have a network created with 200 devices capability design a network cidr for that

size = 200
i should derive number of zeros that helps in concluding number of 1's
then i will choose any private cidr range to create a network cidr
2^n ~= 200 => n=8
so my network can be 
192.168.0.0/(32-8) => 192.168.0.0/24
172.16.0.0/(32-8) => 172.16.0.0/24
10.0.0.0/(32-8) => 10.0.0.0/24

• Scenario-2: Find a private cidr which can accomodate 10000 devices

size = 10000
2^n ~= 10000 => n=14
192.168.0.0/(32-14) => 192.168.0.0/18

• Till now we have been designing one network, lets assume we are designing network for an organization which is a building with 4 stairs, so we need to divide our network into 4 sub networks (subnets)
• So lets understand how to do subnetting
• Scenario-3: We need to connect 1000 devices in our offices with each floor getting 250 devices

Total network size => 1000
2^n ~= 1000 => 10
organization network cidr => 192.168.0.0/22
whole network
ip: 192.168.0.0/22
sm: 11111111.11111111.11111100.00000000

first: 00
second: 01
third: 10
fourth: 11



first floor network
size ~=250 => 2^n ~=250 n => 8

ip: 192.168.0.0/24
ip: 10.10.0.0/24
ip: 172.16.0.0/24
sm: 11111111.11111111.11111111.00000000

second floor 
size ~=250 => 2^n ~=250 n => 8
ip: 192.168.1.0/24


third floor
ip: 192.168.2.0/24

fourth floor
ip: 192.168.3.0/24

• Scenario-4: We need to connect 2000 devices in our offices with each floor getting 500 devices

2^n~=2000
 n = 11

 whole network: 192.168.0.0/21
 sm: 11111111.11111111.11111000.00000000
 00x=> 0
 01x =>010 => 2
 10x => 100 => 4
 11x => 110 => 6


first floor => 500
n => 2^n~=500 => 9
192.168.0.0/23

second floor => 500
n=> 9
192.168.2.0/23

third floor 
192.168.4.0/23

fourth floor
192.168.6.0/23