# VLSM: Variable Length Subnet Mask

Video Activity
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Time
1 hour 19 minutes
Difficulty
Beginner
CEU/CPE
2
Video Transcription
00:01
Hello. Welcome back to Sybers. Create a sub net. Today we're going over veal sm or the variable ink. Sudden. That mask. I would be your instructor. Trend Jiro, Let's go ahead and get it.
00:11
They were gonna divide up an I P. Space with feel sm. This er is here to see is gonna help a lot with making actual proper use of the available I p space
00:22
because you know, you can actually sub net. And let's say you have, like, a slash 24 or something even else you can. Actually, you can block that sub net space off into what you actually need, right?
00:35
So you can actually kind of fit more networks in the one I p. Space. Right. So that's the kind of hole this kind of brings everything together with somebody, right? So I'm gonna go ahead and draw what you might expect here.
00:48
So here, let's just say this is our slash 24 network
00:52
and what we could D'oh eso divide this. And two, it's a different for different networks. So say we could have you know, printers of here. We could have a seat, you know, computers.
01:06
We could have telephones. Um,
01:10
and we could have just a reserve space for future use. Right?
01:15
The future.
01:21
So that's a good way that weaken, So divide our networks. And now let's say someone gets into the telephone network, right? They can't reach the CPU or the printer network or vice versa.
01:34
They're they're just locked into that one logical network, right?
01:40
All right. So what do clear off the screen and let's move on to a little bit of practice.
01:47
We should already be pretty familiar with how to submit networks with previous feels. So I'm gonna go ahead and bring up the pen in here. So what we need to do? We have four different networks media utilize off this network here.
02:02
So what? The department we could do A So we need to do need a block size of 32
02:08
for I t
02:10
accounting.
02:13
We need 32 as well.
02:15
HR, we could do a block size of eight.
02:20
And executives, we need a block size of 64.
02:25
Ah, that's a really executive heavy company. Because I don't know why.
02:31
So what we can actually utilize here We know that we're gonna need 64 p addresses or 32. So what we can do to 56 minus 32? This is gonna give our sudden it masks for us. You see, it's 2 24
02:46
And
02:49
so here we have. You know, you have to be defied. Typified 25 to 54. The way we can figure out the slash or the cider notation on that is you want to add up your
03:00
suddenness. So we have won 28 1 92
03:05
and 2 24 Right, So 1 28 64 32
03:13
So we know that this is going to be a slash 20
03:19
27 this will be the same slash 27.
03:23
So here we can actually go into it a little further.
03:28
So
03:29
due to 56 minus eight
03:32
is going to give us a 2 48 Right?
03:38
So we know that our son I'm asking you going to be a dot to 48
03:40
an HR. So let's do the math here. 1 28 1 92 to 24 to 42. 48. That leaves its five year.
03:52
03:54
so we have a slash 55 plus 24 is a slash 29.
04:01
And we'll do the last one at 64. So we can actually, if you want to, you can kind of be quick about it and just minus one off of this. Right?
04:10
So here, we're gonna have a slash 6 26
04:15
so No. So you got a look at how much empty space we have, so we can actually just add up
04:23
the 32.
04:27
It had these up and see how much space we've utilized.
04:30
So 64 64 1 28 plus eight
04:35
equals 1 36 Sophie, 256 minus 1 36
04:43
Leaves us with 1 20 Right. We have 120
04:46
I p's left and our son that space. So we barely gone over half of our classy network. Right? Instead of just wasting that entire space, we have a whole another space left for future use or for expansion if we need it.
05:00
So it's pretty good utilized. Feel a sound.
05:04
All right, So what we're doing here is we're going to actually imagine that we are the I S P type of thing here,
05:12
and we need to divide our networks out between these various companies. Right?
05:17
So first, we're going to look at the cardboard Shoes company. Their new ICO friendly company that creates couldn't use recycled cardboard for shoes. They are here pretty good until it rains out what otherwise was. Go ahead, move on. We need a total of four slash 24 networks for them, right?
05:34
So what we're gonna do
05:36
is I'm gonna give them 10 100
05:42
slash 24
05:44
and then we're gonna go right up. Make this easy.
05:47
23 Does your slash 24 remember? Because that'll give us a total of four slash 24.
05:54
So you get a little complicated with the slash 23 networks, right?
06:00
So I'm gonna start it out.
06:01
10 140 slash 23. Remember that whole life peace space is going to attend at wonder for the zero through 10.15 to 55.
06:14
So what we can do here is because essentially what we're utilizing is too classy. Networks per slash 23.
06:23
I'm going to take 45 times by two and give us 90. I was gonna go ahead and add 92 are four there, miss a beat through 10 1 94 0 slash 23. So remember, this is also gonna go through 230.95
06:43
2 55 Right. There's our total eyepiece space of utilizing.
06:47
So here we get down to Darrow's fishing charters. Notice two ph fishing. Uh, what we're using is a slash 25. So we're using half of a class seat, that word. Right?
06:59
So we could split this in half and use 33 class C networks,
07:04
so we're gonna use 10 1 96 because I'd be the first next usable through slash 25 that this would just break up our last octet to the 1st 1 27 Right? So if we add 33 to that, we get a total of 1 28 So we got one
07:24
10 that 11 28.
07:27
And remember that last sudden, it has to start with 1 28 because it's ah, splitting half. So this would be on a slash 25 right?
07:36
There is our usable space. So here we have divided this 10 that one done 10 1 network slash 16
07:46
essentially have used half the eyepiece space. Now right. We still have half the eyepiece space that we can give out if we have the treasury for that.
07:53
All right, I'm gonna go ahead and move on here.
07:59
All right? So quiz here. How many slash 24 networks.
08:03
Can we fit inside of a slash 20 to give you a few seconds to kind of do the binary math on this one. If you want to set of your nowhere coast in seven minutes
08:15
already. So I'm gonna break up in here. We're gonna go over this one, so we have us. So I set up my network
08:22
sudden and host. So we're going to use first class full when you have six sub net and hate hosts.
08:31
So what, we're gonna let utilize here, Okay, So we know that we need six by our bets for six. And that is going to equal to 52.
08:41
Come on.
08:43
Rial to 56 minus 2 52 to 50 to give us a total of four. So socially, four classy networks that we can utilize in here. Right? So if you take, for example, 10 1.0
09:01
slash 22 that is going to reach all the way through. 10 1
09:05
32 55. Right?
09:09