## Networking Contd

• Subnets

• consider the following scenario where a network of 2000 devices has to be created, so lets find the possible ip ranges for private network
• Lets define the CIDR Notation and Subnet mask
```cidr: 192.168.0.0/21 sm: 11111111.11111111.11111000.00000000```
• In this network we have 4 blocks and each block requires 500 devices
```host id bits: 2^n ~= 500 host id bits = 9 network id bits = 32-9 = 23```
• Lets create subnets from the overall network 192.168.0.0/21
“`
• </ul>
<h1>overall network</h1>
cidr: 192.168.0.0/21
sm: 11111111.11111111.11111000.00000000
overall sm: 11111111.11111111.11111000.00000000
block sm: 11111111.11111111.11111110.00000000
<hr />
<pre><code> 11111111.11111111.11111xx0.00000000
</code></pre>
block 1 : 11000000.10101000.00000000.00000000 = 192.168.0.0/23
block 2 : 11000000.10101000.00000010.00000000 = 192.168.2.0/23
block 3 : 11000000.10101000.00000100.00000000 = 192.168.4.0/23
block 4 : 11000000.10101000.00000110.00000000 = 192.168.6.0/23
“`

* Lets create 8 subnets for the following requirement

* Lets find out network cidr

``````devices = 8000

2^n ~ = 8000
number of host bits = 13
network id bits = 32-13 = 19
network cidr => x.x.x.x/19 => 172.16.0.0/19

network sm: 11111111.11111111.11100000.00000000

each floor requires 1000 devices
2^n ~ = 1000
host id bits = 10
network id bits = 32-10 = 22

network sm: 11111111.11111111.11100000.00000000
block sm  : 11111111.11111111.11111100.00000000
------------------------------------------------
11111111.11111111.111xxx00.00000000

xxx => 000, 001, 010, 011, 100, 101, 110, 111

ip: 10101100.00010000.00000000.00000000

f1: 10101100.00010000.00000000.00000000 = 172.16.0.0/22
f2: 10101100.00010000.00000100.00000000 = 172.16.4.0/22
f3: 10101100.00010000.00001000.00000000 = 172.16.8.0/22
f4:                                     = 172.16.12.0/22
f5:                                     = 172.16.16.0/22
f6:                                     = 172.16.20.0/22
f7:                                     = 172.16.24.0/22
f8:                                     = 172.16.28.0/22

``````
• We need to create a network for 2 lakh devices we have two datacenters and each datacenter in this network will have 1 lakh devices.
``````overall network => 200000
host bits => 18
network id bits => 32-18 = 14

overall network cidr: 10.0.0.0/14
network sm: 11111111.11111100.00000000.00000000
each subnet => 100000
host bits => 17
network id bits => 32-17 = 15
network sm: 11111111.11111100.00000000.00000000
subnet sm : 11111111.11111110.00000000.00000000
------------------------------------------------
11111111.111111x0.00000000.00000000

network:    00001010.00000000.00000000.00000000 = 10.0.0.0/14

subnet1:    00001010.00000000.00000000.00000000 = 10.0.0.0/15
subnet2:    00001010.00000010.00000000.00000000 = 10.2.0.0/15
``````

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