add Subnetting part 3 VLSM

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[[The Life of a Packet]] [[The Life of a Packet]]
[[Subnetting (Part 1)]] [[Subnetting (Part 1)]]
[[Subnetting (Part 2)]] [[Subnetting (Part 2)]]
[[Subnetting (Part 3 - VLSM)]]

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id: 1777971486-WJIG
aliases:
- Subnetting (Part 3)
tags: []
---
# Subnetting (Part 3 - VLSM)
class B Refference table
| Prefix | Subnets | Hosts |
| ------ | ------- | ----- |
| /17 | 2 | 32766 |
| /18 | 4 | 16382 |
| /19 | 8 | 8190 |
| /20 | 16 | 4094 |
| /21 | 32 | 2046 |
| /22 | 64 | 1022 |
| /23 | 128 | 510 |
| /24 | 256 | 254 |
---
class C Refference table
| Prefix | Subnets | Hosts |
| ------ | ------- | ----- |
| /25 | 2 | 126 |
| /26 | 4 | 62 |
| /27 | 8 | 30 |
| /28 | 16 | 14 |
| /29 | 32 | 6 |
| /30 | 64 | 2 |
| /31 | | (0) |
| /32 | | (0)-2 |
## QUIZ Question 1
You have been given the 172.30.0.0/16. your company requires
100 subnets with at least 500 hosts per subnet. What prefix
length should you use?
I should use 172.168.0.0/23
because it compatible with 100 subnet and 500 hosts
subnet mask -> 255.255.254.0
## Quiz Question 2
What subnet does host 172.21.111.201/20 belong to ?
10101100.00010101.*0110*1111.11001001
172.21.111.201
10101100.00010101.*0110*0000.00000000
172.21.96.0
## Quiz question 3
What is the broadcast address of the network 192.168.91.78/26
11000000.10101000.10110011.*01*001110
192.168.91.78
11000000.10101000.10110011.*01*111111
192.168.91.127
## Quiz question 4
You divide the 172.16.0.0/16 network into 4 subnets of equal size.
Identify the network and broadcast addresses of the second subnet
Subnet 1 :
Network address
172.16.0.0/18
10101100.00011010.*00*000000.00000000
broadcast:
172.16.0.0/18
10101100.00011010.*00*111111.00000000
172.16.63.255/18
Subnet 2 :
Network address
172.16.64.0/18
10101100.00011010.*01*000000.00000000
broadcast:
172.16.65.0/18
10101100.00011010.*01*111111.00000000
172.16.127.255/18
Subnet 3 :
Network address
172.16.128.0/18
10101100.00011010.*10*000000.00000000
broadcast:
172.16.128.0/18
10101100.00011010.*10*111111.00000000
172.16.191.255/18
Subnet 4 :
Network address
172.16.192.0/18
10101100.00011010.*11*000000.00000000
broadcast:
172.16.192.0
10101100.00011010.*11*111111.00000000
172.16.255.255/18
## Quiz question 5
You divide the 172.30.0.0/16 network into subnets of 1000 hosts each. How many subnets
are you able to make
I'm able to make 64 subnets
## Subentting class A Networks
The process of subnetting Class A, Class B and Class C networks is Exactly the same !
### Example 2
You hace been given the 10.0.0.0/8 network. You must create 2000 subnets which
will be distributed to various enterprises.
What prefix length must you use ?
How many host addresses usable addresses will be in each subnet?
10.0.0.0
00001010.00000000.0000000.0000000
2, 4, 8, 16,32, 64,128,256, 512, 1024, 2048
00001010.*00000000.000*00000.0000000
Answer:
10.0.0.0/19
8192 - 2 = 8190 hosts
### Example 2
PC1 has an IP address of 10.217.182.223/11.
Identify the following for PC1's subnet:
1) Network address:10.192.0.0/11
2) Broadcast address: 10.223.255.255
3) First usable address: 10.192.0.1
3) Last usable address:10.223.255.254
3) Nuber of host (usable) address: 2,097,150
10.217.182.223
00001010.*110*11001.10110110.11011111
## [[VLSM]]
Variable-Length Subnet Masks
- Until now, we have practiced subentting used FLSM (Fixed-Length Subnet Masks).
- This means that all of the subents use the same prefix length (ie. subnetting a class C
into 4 subenets using /26).
- VLSM (Variable-Length Subnet Masks) is the process of creating subnets of different sizes
to make your use of network addresses more eficient
- VLSM is more complicated than FLSM, but it's easy if you folow the steps correctly.
### Exaple 1
We must divide 192.168.1.0/24 must divided between 5 subnets
Tokyo Lan A = 110 Hosts --- Tokyo Lan B = 8 Hosts
|
Router
|
Router
|
Toronto Lan A = 29 Hosts --- Toronto Lan B = 45 Hosts
#### VLSM Steps
1) Assign the largest subnet at the start of the address space.
2) Assign the second- largest subnet after it.
3) Repeat the process until all subnets have been assigned
we will do this in this order
Tokyo LAN A -> Toronto LAN B -> Toronto LAN A -> Tokyo LAN B -> Point to point
##### Tokyo LAN A
Network address: 192.168.1.0/25
Broadcast address: 192.168.1.127/25
First usable address: 192.168.1.1/25
Last usable address: 192.168.1.126/25
Total Number of usable host address: 126
##### Toronto LAN B
if we add 1 to the Tokyo Broadcast address we get the next Network address
Network address: 192.168.1.128/26
Broadcast address: 192.168.1.191/26
First usable address: 192.168.1.129/26
Last usable address: 192.168.1.190/26
Total Number of usable host address: 62
##### Toronto LAN B
Network address: 192.168.1.192/27
Broadcast address: 192.168.1.223/27
First usable address:192.168.1.193/27
Last usable address:192.168.1.222/27
Total Number of usable host address:30
##### Tokyo LAN A
Network address: 192.168.1.224/28
Broadcast address: 192.168.1.239/28
First usable address: 192.168.1.225
Last usable address: 192.168.1.239
Total Number of usable host address: 14
##### Point to Point
Network address: 192.168.1.240/30
Broadcast address: 192.168.1.243/30
First usable address: 192.168.1.241/30
Last usable address: 192.168.1.242/3
Total Number of usable host address: 2
## Additional Practice
- https://www.subnettingquestions.com
- https://www.subnetting.org
- https://www.subnettingpractice.com