In the previous video, we already learn about Public IP Address and Private IP Address. 2
Now in this video we are going to start learning about subnetting. 3
Okay, do you remember why we need to learn subnetting? 4
Yes! We need to learn subnetting to determine the best prefix we will use in the network. 5
For example, here we have a computer network that consist 6
of 12 computers. So in this case, we will need 12 IP for each computers. 7
The question is, which prefix is the best for 12 IP or 12 computers? 8
In the previous video, I say that if we use prefix /24, the total IP is 256. 9
How we can get this 256? we are going to learn about this now. 10
To get this 256 is 2 to the power of 32 minus prefix. 11
In this case, the prefix is 24, so the total IP is 2 to the power of 8. Because 32 minus 24 12
is 8. And 2 to the power of 8 is 256. This is how we get 256 for prefix /24. 13
The question is, why 32? this is because IP Address is consist of 32 bit. 14
Oh ya, this formula is the easyway to learn about subnetting. If you want to learn 15
subnetting in the hardway, you will need to convert this IP Address to binary first, 16
doing some calculation in the binary, and then convert it back to the decimal. 17
I will not teach you the hardway in this course. 18
Because if we learn in the hardway, everyone of you will think that computer network is difficult! 19
In this course, I want to make the computer network as simple as possible. 20
So you can happy to learn about computer network. 21
Okay, back to this. Now let’s review this again, so here we have prefix /24, the total IP is 256, 22
we can get this 256 from 2 to the power of 32 minus prefix, 32 minus 24 is 8. And 2 to the power of 8 is 256. 23
May be some of you have a trouble to determine 2 to the power of 8. So I will give you another easier example. 24
Let’s say we have prefix /30. How many IP Address that we can use in prefix /30? 25
2 to the power of 32 minus 30, 32 minus 30 is 2, so 2 to the power of 2, 26
I think all of you will know the answer right? Yes.. 2 to the power of 2 Is 4. 27
Now let’s try another example. Let’s say we have prefix /29. How many IP Address that we can use 28
in prefix /29? Let’s try to calculate. 2 to the power of 32 minus 29. 32 minus 29 29
is 3, so 2 to the power of 3, the answer is 8. So the total IP that we can use in prefix /29 is 8, 30
Well, if you see here, actually we have a patterns. 2 to the power of 2 is 4, 31
2 to the power of 3 is 8. This is means that if the power increment by 1, the result is multiply by 2. 32
Let’s write it out. 2 to the power of 1 is 2, 2 to the power of 2 is 4, 2 to the power of 3 is 8, 33
2 to the power of 4 is 16, 2 to the power of 5 is 32, and others. 34
If you see the patterns, here we just need to multiply the result by 2. 2 to the power of 2 35
is 2 multiply by 2, which is 4. 2 to the power of 3 is 4 multiply by 2, which is 8. 36
2 to the power of 4 is 8 multiply by 2, which is 16. 2 to the power of 5 is 16 multiply by 2, 37
which is 32, 2 to the power of 6 is 32 multiply by 2, which is 64. 2 to the power of 7 38
is 64 multiply by 2, which is 128, and 2 to the power of 8 is 128 multiply by 2, which is 256. 39
So the pattern is that we just need to multiply the result by 2. 40
We don’t need to have a trouble to calculating powers anymore. 41
Okay, here we stop in 2 to the power of 8. Because this is for prefix /24, in this course we will only 42
learn about subnetting prefix /24 until /30. So we just need to know until 2 to the power of 8. 43
Okay, now I hope you understand how to determine 44
how much IP Address that we can use in the specific prefix. 45
Before I end this video, let’s try one more example to make sure that you really understand. 46
Let’s say we have prefix /26, the total IP for this prefix is 2 to the power of 32 minus 26. 32 minus 26 is 6, 47
so 2 to the power of 6, and the result is 64. So the total IP that we can use in prefix /26 is 64. 48
Now let’s back to our first case. Here we have 12 PC, and absolutely we will need 12 IP Address. 49
The question is which prefix is the best for this case? 50
The answer is very simple, we just need to see in the our calculation before. 51
Here we have 2 to the power of 1, the result is 2. Absolutely this is not enough for us 52
4 is also not enough, 8 not enough, and finally, 16 is absolutely enough. 53
16 is enough for 12 PC. And this is the best. 54
So which prefix the best? This is easy, the prefix is 32 minus 4. Which is /28. 55
So in the computer network that consist of 12 PC, the best prefix that we can use is prefix /28. 56
Okay I hope now you understand how to find the best prefix that we can use in the computer network. 57
In the next video, we are going to learn another case to find the best prefix we will use. 58
Thankyou for watching and see you on the next video!