Subnetting

• Subnetting helps us divide network into smaller networks/sub networks which we refer as subnet.
• private cidr ranges

10.0.0.0/8
172.16.0.0/12
192.168.0.0/16

• I need to create private network for 2000 devices approximately

Network:
2^n ~= 2000
n = 11
N = 32 -11 = 21

Network SM: 11111111.11111111.11111000.00000000
ip: 192.168.0.0/21

• Divide this network into two subnets of sizes 1000 each.

subnet size:

2^n ~= 1000
n = 10
N = 32-10 = 22

Network SM: 11111111.11111111.11111000.00000000
Subnet SM:  11111111.11111111.11111100.00000000
------------------------------------------------
                      192.168.00000x00.0/22
                      192.168.00000000.0/22 => 192.168.0.0/22
                      192.168.00000100.0/22 => 192.168.4.0/22

• Lets create a network of 1000 devices with 4 subnets of 200 devices approximately

Network:
2^n ~= 1000
n = 10
N = 22
ip cidr: 192.168.0.0/22

Network SM: 11111111.11111111.11111100.00000000

subnet ~= 200
2^n ~= 200
n = 8
N = 32-8 = 24

Network SM: 11111111.11111111.11111100.00000000
Subnet  SM: 11111111.11111111.11111111.00000000
------------------------------------------------
                      192.168.000000xx.0/24 
                      192.168.00000000.0/24 => 192.168.0.0/24
                      192.168.00000001.0/24 => 192.168.1.0/24
                      192.168.00000010.0/24 => 192.168.2.0/24
                      192.168.00000011.0/24 => 192.168.3.0/24

• Create a network of 2000 devices with 4 subnets of 500 each

Network Size: 2000
2^n ~= 2000
n = 11
N = 32-11 = 21
ip: 10.0.0.0/21
Network SM: 11111111.11111111.11111000.00000000

Subnet: 500
2^n ~= 500
n = 9
N = 32 -9 = 23


Network SM: 11111111.11111111.11111000.00000000
Subnet  SM: 11111111.11111111.11111110.00000000
------------------------------------------------
                         10.0.00000xx0.0/23
                         10.0.00000000.0/23 => 10.0.0.0/23
                         10.0.00000010.0/23 => 10.0.2.0/23
                         10.0.00000100.0/23 => 10.0.4.0/23
                         10.0.00000110.0/23 => 10.0.6.0/23

• Exercise: Create a network of size of approximately 160000 devices with 16 subnets of 8 thousand each.
• Create a network of 400000 devices with 8 subnets of 50000 each

Network size : 4 lakhs
2^n ~ = 400000
n = 19
N = 32-19 = 13

cidr range: 172.16.0.0/13
Network SM: 11111111.11111000.00000000.00000000

Subnet Size: 50000
2^n ~= 50000
n = 16
N = 32-16 = 16

Network SM: 11111111.11111000.00000000.00000000
Subnet  SM: 11111111.11111111.00000000.00000000
------------------------------------------------
                 172.00010xxx.0.0/16
                 172.00010000.0.0/16 => 172.16.0.0/16
                 172.00010001.0.0/16 => 172.17.0.0/16
                 172.00010010.0.0/16 => 172.18.0.0/16
                 172.00010011.0.0/16 => 172.19.0.0/16
                 172.00010100.0.0/16 => 172.20.0.0/16
                 172.00010101.0.0/16 => 172.21.0.0/16
                 172.00010110.0.0/16 => 172.22.0.0/16
                 172.00010111.0.0/16 => 172.23.0.0/16