add dday 2 subnetting

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[[Static Routing]]
[[The Life of a Packet]]
[[Subnetting (Part 1)]]
[[Subnetting (Part 2)]]

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14. Subnetting (Part 2).md Normal file
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id: 1777871422-VTLQ
aliases:
- Subnetting (Part 2)
tags: []
---
# Subnetting (Part 2)
## Question
45 hosts -> SW1->+--+<-SW3<-45 hosts
|R1|
45 hosts -> SW2->+--+<-SW4<-45 hosts
Divide the 192.168.1.0/24 network into four subnets that can accommodate
the number of hosts required.
The first subnet (Subnet 1) is 192.168.1.0/26 What are the remaining subnet
Hint: Find the broadcast address of Subnet 1. The next address is the network address of
Subnet 2. Repeat the process for Subnets 3 and 4
### Subnet 1
Subnet 1: 192.168.1.0/26
11000000.10101000.00000001.00**000000**
192 . 168 . 1 . 0
broadcast address:
11000000.10101000.00000001.00**111111**
192 . 168 . 1 . 63
192.168.1.0 to 192.168.1.63
### Subnet 2
Subnet 2: 192.168.1.64/26
11000000.10101000.00000001.01**000000**
192 . 168 . 1 . 64
11000000.10101000.00000001.01**111111**
192 . 168 . 1 . 127
192.168.1.63 to 192.168.1.127
### Subnet 3
Subnet 3: 192.168.1.128/26
11000000.10101000.00000001.10**000000**
192 . 168 . 1 . 128
11000000.10101000.00000001.10**111111**
192 . 168 . 1 . 191
192.168.1.128 to 192.168.1.191
### Subnet 4
Subnet 4: 192.168.1.192/26
11000000.10101000.00000001.11**000000**
192 . 168 . 1 . 192
11000000.10101000.00000001.11**111111**
192 . 168 . 1 . 255
192.168.1.192 to 192.168.1.255
### Trick
By adding 64 the last bit of the network portion you can find the network address
## Subnetting
11000000.10101000.00000001.0**0000000**
192.168.255.0
11000000.10101000.11111111.1**0000000**
192.168.255.0
Borrowing 1 bit = can make 2 subnets
### Formulas
2^x = number of subnets
(x=number of 'borrowed' bits)
2^n-2 = number of hosts
(x=number of hosts bits)
## Identify the subnet
What subnet does host 192.168.5.57/27 belong to?
11000000.10101000.00000101.00111001
192.168.5.57
The borrowed bits are
11000000.10101000.00000101.**001**11001
to find the network address we need to change the host bits by zero
11000000.10101000.00000101.**001**00000
192.168.5.32
What subnet does host 192.168.29.219/29 belong to?
11000000.10101000.00011101.**11011**011
192.168.29.219
to find the network address we need to change the host bits by zero
11000000.10101000.00011101.**11011**000
192.168.29.216
## Subnets / hosts (class C)
| Prefix Length | Number of subnets | Number of Hosts |
| ------------- | ----------------- | --------------- |
| /25 | 2 | 126 |
| /26 | 4 | 62 |
| /27 | 8 | 30 |
| /28 | 16 | 14 |
| /29 | 32 | 6 |
| /30 | 64 | 2 |
| /31 | 128 | 0 (2) |
| /32 | 156 | 0 (1) |
## Subenetting Class B
The process of subnetting Class A, Class B and Class C networks is :
Exactly the same !
### Example 1
You have been given the 172.16.0.0/16 network. You are asked to create 80
subnets for your company's various LANs, What prefix length should you use ?
172.16.0.0/16
10101100.00010000.00000000.00000000
172 . 16 . 0 . 0
We have to borrow 7 bits = 128 subnets
10101100.00010000.**0000000**0.00000000
172 . 16 . 0 . 0
### Example 2
You have been given the 172.22.0.0/16 network. You are asked to create 500
subnets for your company's various LANs, What prefix length should you use ?
172.22.0.0/16
10101100.00010000.00000000.00000000
172 . 22 . 0 . 0
We have to borrow 9 bits = 512 subnets = /25
10101100.00010000.**00000000.0**0000000
172 . 22 . 0 . 0
### Example 3
You have given the 172.18.0.0/16 network. Your company requires 250 subnets with the
same number of hosts per subnet. What prefix length should you use
172.18.0.0
10101100.00010000.00000000.00000000
172 . 18 . 0 . 0
We have to borrow 8 bits = 256 subnets = /24
10101100.00010000.**00000000**.00000000
172 . 18 . 0 . 0
## Subnets / hosts (class B)
| Prefix Length | Number of subnets | Number of Hosts |
| ------------- | ----------------- | --------------- |
| /17 | 2 | 32766 |
| /18 | 4 | 16382 |
| /19 | 8 | 8190 |
| /20 | 16 | 4094 |
| /21 | 32 | 2044 |
| /22 | 64 | 1022 |
| /23 | 128 | 510 |
| /24 | 256 | 254 |
| /25 | 2 | 126 |
| /26 | 4 | 62 |
| /27 | 8 | 30 |
| /28 | 16 | 14 |
| /29 | 32 | 6 |
| /30 | 64 | 2 |
| /31 | 128 | 0 (2) |
| /32 | 156 | 0 (1) |
## Review
- Subnetting practice questions (class C networks)
- Subnetting Class B networks