# VLSM

Video Activity
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Time
23 hours 18 minutes
Difficulty
Beginner
CEU/CPE
23
Video Transcription
00:00
Hello and welcome back to I C d one interconnecting Cisco networking devices apart. One this episode for 13 variable ink subnet mask.
00:08
I am friend. There will be a structure for this course in the last video went over How to determine you're addressing needs
00:15
and what your sudden eyes might look like
00:18
this up. So we're gonna go over the variable length subnet mask and utilizing that space most efficiently.
00:26
So again, we're gonna look a variable length of us. Um, we're gonna have a quick exercise at the end.
00:32
So see, if you remember how many hosts per sudden, it would've slashed 20 to come, too.
00:38
So think about it for a second. Think about how many network. But you have. Then think about how many sub net bits you have. And then think about how money no host bits you'd have.
00:48
So what, you go through that real quick?
00:53
All right? It is 10 24. And if you guys always want to What I utilize just to make sure I had it down when I was when I was learning it, bring up on I p subject calculator on gun golf. Google. Um, do all the math to make sure you got everything. You're you're sure that it's right
01:11
and then plug it in on their very, you know, verified that you're doing it right.
01:15
It doesn't hurt.
01:18
Are so variable ink Suddenly mess. Think of it as,
01:22
ah, a pie, Right. We r I p address space that we have Our block space is a pie.
01:27
So if we equalize that in four, that's cool. Each person gets four bits, But let's say,
01:34
you know, one person only wants a tiny bit. He only needs two addresses to do. We need to have 128 addresses for him of elbow. No, absolutely not. Um, so splitting. Apply unequally, but appropriately.
01:49
So
01:51
I think about it. As you know, the last one where we had 128 addresses for the two router to buy peace that we needed.
02:00
02:04
Um,
02:05
So what this does is it fills the space efficiently, inappropriately,
02:08
so we could take a slash 24 which has 256 miles to addresses network I D and broadcast.
02:15
Um, I was gonna assume I'm a state without those. From now on, they could be filled with a slash 34 between the routers, which will give you two usable I P addresses slash 27 would give you 30 usable. My peas
02:30
slash 26 62. Usable slash 25 give 126 usable. That leaves us with a total of 28 addresses left, which you could fill with. Um,
02:43
you know, a couple other you could feel it, like three more sub nets.
02:46
All right,
02:47
02:53
So we'll go ahead and jump right into the same exercise that we had last time. And let's think about if we can subdivide this a little more appropriately.
03:02
So again, we have him
03:05
in the largest here at 126.
03:07
So our network is still 16.
03:12
So, basically, what we're gonna do is re create a box like this for each network.
03:16
So we're gonna do this 1st 1 here,
03:20
and I'm gonna draw out this
03:23
just cause that and I don't know, that's what I always do.
03:25
it helps me
03:28
under 20 eights to 36 5 12 24
03:32
And let's see, we need this block. So you have 107 and nine.
03:39
So again, at least with 126 usable with a 512 sub nets.
03:46
Um,
03:47
so now we've only used half of Ah,
03:52
um fourth act it there
03:54
and what to do the same for this one. This will actually be the same thing because you are the next largest is gonna be 64 1 21 can't fit in there.
04:03
It's gonna be safer, this guy. But these two,
04:09
let's do a picture over here so sudden it's
04:14
network and host.
04:17
So network is gonna be 16 again. So let's go through the 54 1st on down 64.
04:27
So that will give us six for the host bits,
04:31
which would give us. So it's 32. That would give us 10
04:35
on the sub now,
04:38
which will give us a total of 124 segments of. But since we're utilizing the
04:44
variable length and this work should be the same thing, because remember, we can't do the 32 blocks space because we had to minus two off of the space there.
04:54
So using the 32 here would actually only give us 30 usable eyepiece.
04:59
So let's think about it. Here we have.
05:01
I was gonna do the last bit, so we got 17 to 18.
05:06
Zero dots,
05:10
zero through 1 20
05:12
five.
05:14
Here
05:15
it will do. 1 26 minus 2 35
05:20
Is that zero? So now this one's gonna move into the 00.1 dot zero through.
05:27
Got one dots
05:30
too, huh?
05:31
1 25 Sorry.
05:33
Heard out. Once way seven. Right on that one.
05:35
27
05:38
05:45
for now. Just shorthand.
05:47
You're lazy.
05:48
So when we have that 1.1 28 through,
05:54
it's a 0.64
05:56
we go through that one, that 1 91
06:00
and this one will be
06:01
one night a year dot Won that 1 92
06:05
Well, 64. So that would bring us straight to wonder to 55.
06:11
So it's still wasting this entire slash 16. We've now divided this. We are at our address. Space that we currently use goes from here.
06:20
217 to 18 dot
06:25
one that to 55. So he only used this much space
06:30
instead of wasting an entire slash 16 on this.
06:33
So this is what I'm talking about using more sufficiently. Um, and then you still have to create the slash thirties for this slash thirties of the usual ones that gives you you too. I p's poor for each.
06:46
Um, if reached space there,
06:48
really go ahead and move into the post assessments.
06:54
What would these side annotation be for the printer sub net if we have 63 devices with no need for expansion? By that, I mean, don't worry about future planning. Assume that we have 63 devices. We need to create a sub net like now for it.
07:06
And remember, minus, you're too. For usable. I P addresses for the network and broadcast.
07:13
Give me a few seconds.
07:17
It is going to be a slash 25
07:20
because remember,
07:24
we got a plan.
07:28
All right, remember,
07:30
if we have sudden it
07:32
and with network
07:36
host,
07:38
so the way I always do it is break. He's up in 8 16 24 So this one and the next closest is 24.
07:46
07:48
We need to have if we drill a chart out
07:51
248
07:54
16 30 to 64 1
07:59
one
08:01
with that 1 28
08:03
Um,
08:05
so we can try mirror 64 minus two. Would Billy leave a 62 years aboard eyepiece? So we had to go all the way to here,
08:11
which is 1234567 on the host,
08:18
which would leave us one here.
08:20
So we have to sub nets
08:24
with 100 28 blocks. Eyes
08:28
with 126 usable
08:33
my piece.
08:35
And the next lesson we're gonna look at classical I P v four addresses again,
08:39
maybe a little bit of a review. But we're also gonna go in death a little bit more than we did previously.
08:45
And if you have questions, need any help. Feel free to shoot me. Message. Otherwise, thank you for watching this lesson. I look forward to seeing the next one
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