Private Network vs Public Network

• Public Network: A network which can be accessed from internet
• Private Network: A network which cannot be accessed directly from internet.
• For private networks there are some predefined or reserved cidr ranges
  
• CIDR Ranges
  • 10.0.0.0/8
  • 172.16.0.0/12
  • 192.168.0.0/16

Subnet

• Network can be divided into multiple smaller networks called as subnets

Consider a building with 4 floors, we need to design a network

• Each floor requires around 200 devices to be connected
• Total building around 800 devices
  
• for building N = 22

building network cidr: 192.168.0.0/22

each floor N = 24

building SM: 11111111.11111111.11111100.00000000
floor SM:    11111111.11111111.11111111.00000000
            -------------------------------------
                                     xx
                                     00 => 192.168.0+(0).0/24
                                     01 => 192.168.0+(1).0/24
                                     10 => 192.168.0+(2).0/24
                                     11 => 192.168.0+(3).0/24
                                     192.168.0.0/24
                                     192.168.1.0/24
                                     192.168.2.0/24
                                     192.168.3.0/24

• Each floor requires around 20000 devices to be connected

each floor ~= 20000
2^n ~= 20000
n = 15
N = 17

building ~= 80000
2^n ~= 80000
n = 17
N = 15

building => x.x.x.x/15 => 172.16.0.0/15

bd SM: 11111111.11111110.00000000.00000000
fl SM: 11111111.11111111.10000000.00000000
      ---------------------------------------
                       x.x    
                       0.0  => 172.(16+0).0.0/17 => 172.16.0.0/17
                       0.1  => 172.(16+0).128.0/17 => 172.16.128.0/17
                       1.0  => 172.(16+1).0.0/17 => 172.17.0.0/17
                       1.1  => 172.(16+1).128.0/17 => 172.17.128.0/17

• Consider building has 8 floors, each floor requires 60 devices

floor ~= 60
2^n ~= 60
n = 6
N = 26

building = 480
2^n ~= 480
n = 9
N = 23
10.0.0.0/23


bd SM:  11111111.11111111.11111110.00000000
fl SM:  11111111.11111111.11111111.11000000
                         -------------------
                                 x.xx  
                                 0.00  => 10.0.0.0/26
                                 0.01  => 10.0.0.64/26
                                 0.10  => 10.0.0.128/26
                                 0.11  => 10.0.0.192/26
                                 1.00  => 10.0.1.0/26
                                 1.01  => 10.0.1.64/26
                                 1.10  => 10.0.1.128/26
                                 1.11  => 10.0.1.192/26

• Consider a building with 8 floors and each floor requires 25000 devices

floor ~= 25000
2^n ~= 25000
n = 15
N = 17

building ~= 200000
2^n ~= 200000
n = 18
N = 14

10.0.0.0/14

bd SM: 11111111.11111100.00000000.00000000
fl SM: 11111111.11111111.10000000.00000000
       -------------------------------------
                      xx.x
                      00.0   => 10.0.0.0/17
                      00.1   => 10.0.128.0/17
                      01.0   => 10.1.0.0/17
                      01.1   => 10.1.128.0/17
                      10.0   => 10.2.0.0/17
                      10.1   => 10.2.128.0/17
                      11.0   => 10.3.0.0/17
                      11.1   => 10.3.128.0/17