Networking continued

• CIDR Expansion

172.16.0.0/12

ip:      172.      16.       0.       0
         172.0001xxxx.xxxxxxxx.xxxxxxxx
         172.00010000.00000000.00000000 = 172.16.0.0
         172.00011111.11111111.11111111 = 172.31.255.255
SM: 11111111.11110000.00000000.00000000

• What is bigger network (A)
  • A. 10.10.0.0/17
    • Size = 2 ^ (32-17) -2 ~= 2^15
  • B. 10.10.0.0/18
    • Size = 2^ (32-18) -2 ~= 2^14

subnetting

• Process of creating multiple subnets from a larger network is called as subnetting
• Subnet => sub network

Scenario 1: Create a network of 1000 devices with 4 subnets

• overview
  
• Assumptions:
  • We are creating private network
  • private network will have only the following ranges Refer Here
    • 10.0.0.0 to 10.255.255.255 (10.0.0.0/8)
    • 172.16.0.0 to 172.31.255.255 (172.16.0.0/12)
    • 192.168.0.0 to 192.168.255.255 (192.168.0.0/16)
• Lets find CIDR range of Network

2^n -2 ~= 1000
n = 10
N = 32-10 = 22
CIDR: 10.0.0.0/22

• Lets find the CIDR Range for subnets

2^n - 2 ~= 250
n = 8
N = 32-8 = 24

Network SM: 11111111.11111111.11111100.00000000
Subnet SM:  11111111.11111111.11111111.00000000
           -------------------------------------
                  10.       0.000000yy.00000000
                  10.       0.00000000.00000000 = 10.0.0.0/24
                  10.       0.00000001.00000000 = 10.0.1.0/24
                  10.       0.00000010.00000000 = 10.0.2.0/24
                  10.       0.00000011.00000000 = 10.0.3.0/24

Scenario 2

• I need a network of 20000 devices with 2 subnets (10000 in each subnet)
• Network CIDR

2^n - 2 ~= 20000
n = 15
N = 32-15 = 17

CIDR: 192.168.0.0/17

• Subnet CIDR

2^n - 2 ~= 10000
n = 14
N = 32 -14 = 18

• Subnetting

Network SM: 11111111.11111111.10000000.00000000
Subnet  SM  11111111.11111111.11000000.00000000
-------------------------------------------------
                 192.     168.0y000000.
                 192.     168.00000000.  => 192.168.0.0/18
                 192.     168.01000000.  => 192.168.64.0/18

Scenario 3

• Create 4 subnets of size 120 each to form a network of size 480
• Network

2^n -2 ~= 480
n = 9
N = 32-9 = 23
CIDR = 192.168.0.0/23

• Subnet

2^n -2 ~= 120
n = 7
N = 32-7 = 25

• Subnetting

Network SM: 11111111.11111111.11111110.00000000
subnet  SM: 11111111.11111111.11111111.10000000
-------------------------------------------------
                 192.     168.0000000y.y0000000
                 192.     168.00000000.00000000 => 192.168.0.0/25
                 192.     168.00000000.10000000 => 192.168.0.128/25
                 192.     168.00000001.00000000 => 192.168.1.0/25
                 192.     168.00000001.10000000 => 192.168.1.128/25

Scenario 4

• I need 8 subnets each with 20000 devices
• Total = 160000 (Network)
• Network

2 ^ n - 2 ~= 160000
n = 18
N = 14
172.16.0.0/14

• Subnet

2^n =2 ~= 20000 = 15
N = 32 -15 = 17

• Subnetting

Network SM:  11111111.11111100.00000000.00000000
Subnet  SM:  11111111.11111111.10000000.00000000
--------------------------------------------------
                  172.000100yy.y0000000
                  172.00010000.00000000 => 172.16.0.0/25
                  172.00010000.10000000 => 172.16.128.0/25
                  172.00010001.00000000 => 172.17.0.0/25
                  172.00010001.10000000 => 172.17.128.0/25
                  172.00010010.00000000 => 172.18.0.0/25
                  172.00010010.10000000 => 172.18.128.0/25
                  172.00010011.00000000 => 172.19.0.0/25
                  172.00010011.10000000 => 172.19.128.0/25

• Excerise:
  • design a private network with 16 subnets with each subnet of size 60 devices