1
00:00:00,000 --> 00:00:00,499

2
00:00:00,499 --> 00:00:02,850
I'd like you to imagine
that you and I have shown up

3
00:00:02,850 --> 00:00:05,070
for work one day,
and our boss meets us

4
00:00:05,070 --> 00:00:07,074
with a big smile on
their face and says,

5
00:00:07,074 --> 00:00:09,240
can you help me with a small
project I'm working on?

6
00:00:09,240 --> 00:00:10,698
And we say, sure,
what do you need?

7
00:00:10,698 --> 00:00:13,410
And our boss shows us
this topology right here.

8
00:00:13,410 --> 00:00:15,880
And they ask us, can
you put this together?

9
00:00:15,880 --> 00:00:17,400
We have a pilot
program we're doing

10
00:00:17,400 --> 00:00:18,960
and I want to just
test them things.

11
00:00:18,960 --> 00:00:20,202
Can you make that all happen?

12
00:00:20,202 --> 00:00:20,910
And we say, sure.

13
00:00:20,910 --> 00:00:23,550
We've got some extra gear
so we round up some routers

14
00:00:23,550 --> 00:00:25,360
and we connect
them with switches.

15
00:00:25,360 --> 00:00:27,570
And then we can go ahead
and do the addressing.

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00:00:27,570 --> 00:00:30,960
Maybe over here on this network,
that is common to our R3, R1,

17
00:00:30,960 --> 00:00:37,360
and R2, we use the
network 192.168.1.0/24.

18
00:00:37,360 --> 00:00:39,360
Now if we analyze
that, that means

19
00:00:39,360 --> 00:00:42,700
that the first 24
bits of this number,

20
00:00:42,700 --> 00:00:46,100
which is the first three
octets, are the network.

21
00:00:46,100 --> 00:00:49,080
And this last octet is
available for host addressing.

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00:00:49,080 --> 00:00:52,760
And then for this network
right here, between R2 and R4,

23
00:00:52,760 --> 00:01:00,260
maybe we use the 192.168.2.0/24.

24
00:01:00,260 --> 00:01:04,760
And for the network between
R4, R5, and R6, right here,

25
00:01:04,760 --> 00:01:10,980
maybe we use the
network 192.168.3.0/24.

26
00:01:10,980 --> 00:01:13,040
Now once we've implemented
these IP addresses,

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00:01:13,040 --> 00:01:15,650
we go back to our boss all proud
and say, hey, we're all done.

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Take a look.

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00:01:16,550 --> 00:01:19,400
And he looks at it on
paper and says, oh.

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00:01:19,400 --> 00:01:21,110
I forgot to tell you something.

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00:01:21,110 --> 00:01:22,869
And we say, oh, what's that?

32
00:01:22,869 --> 00:01:24,410
And the boss says,
this kind of needs

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00:01:24,410 --> 00:01:26,700
to fit into our
existing network.

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00:01:26,700 --> 00:01:30,050
And if you could, says the boss,
I need this entire topology

35
00:01:30,050 --> 00:01:38,570
to fit in the space
of 192.168.5.0/24.

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00:01:38,570 --> 00:01:43,670
I want to use that network to
support this entire topology.

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00:01:43,670 --> 00:01:45,770
Now at that point, we
have a couple of options.

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One, we can say, this is
only one network address.

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We have three individual
separate networks

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that we need to deal with.

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00:01:53,360 --> 00:01:55,760
We have network A,
network B, network C.

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00:01:55,760 --> 00:01:59,300
We could argue that we need
more IP addressing space.

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Or the other option,
my friend, is

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00:02:02,000 --> 00:02:05,300
to go ahead and do
custom subnetting.

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00:02:05,300 --> 00:02:08,600
The process of subnetting
is simply taking an existing

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00:02:08,600 --> 00:02:11,300
network space, that we're
given, and chopping it

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00:02:11,300 --> 00:02:14,270
up into smaller pieces.

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00:02:14,270 --> 00:02:17,240
Sort of like if we had
Sunset Street, for example,

49
00:02:17,240 --> 00:02:19,700
and we needed to break that
up into smaller sections.

50
00:02:19,700 --> 00:02:23,630
Maybe we could have
like Sunset Boulevard,

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00:02:23,630 --> 00:02:29,300
Sunset Avenue, Sunset Lane,
and we can break it up.

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00:02:29,300 --> 00:02:32,300
All we're doing when we're
doing custom subnetting,

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00:02:32,300 --> 00:02:35,210
is we're taking
one network address

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00:02:35,210 --> 00:02:38,300
space like the
192.168.5 network,

55
00:02:38,300 --> 00:02:41,220
and we are going to chop
it up into smaller pieces

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00:02:41,220 --> 00:02:44,420
so we can make additional,
smaller networks.

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00:02:44,420 --> 00:02:46,970
Now unfortunately,
there is a price

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00:02:46,970 --> 00:02:48,590
that's going to
be paid if we take

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00:02:48,590 --> 00:02:53,060
a perfectly good network like
192.168.5 and we chop it up.

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00:02:53,060 --> 00:02:56,780
This network, which currently
has 24 bits for the network

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00:02:56,780 --> 00:03:00,020
and an eighth bit over
here for the host portion,

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00:03:00,020 --> 00:03:03,530
in order to do custom
subnetting, what we have to do

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00:03:03,530 --> 00:03:08,090
is we're going to say goodbye
to a few good host bits.

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00:03:08,090 --> 00:03:10,410
Those 8 host bits,
which are over here,

65
00:03:10,410 --> 00:03:12,820
we're going to have to
sacrifice some of them.

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Did I say have to?

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00:03:13,940 --> 00:03:15,510
And the answer is, yes.

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We are going to voluntarily
take some of the bits

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00:03:18,480 --> 00:03:21,020
over in this host
portion from the network

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00:03:21,020 --> 00:03:22,350
that we're dealing with.

71
00:03:22,350 --> 00:03:25,280
And we are going to
allocate some of those bits

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00:03:25,280 --> 00:03:27,207
over towards network addressing.

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00:03:27,207 --> 00:03:28,790
And effectively,
what it's going to do

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00:03:28,790 --> 00:03:32,330
is it's going to make more
room for network address space.

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00:03:32,330 --> 00:03:35,300
And we can use that additional
space, those additional bits,

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to carve out additional subnets.

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00:03:37,970 --> 00:03:39,630
Let's use a practical
example here.

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00:03:39,630 --> 00:03:46,110
Let's say we do have a
192.168.5.0/24 network.

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And we have to use that major
network to go ahead and create

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00:03:50,510 --> 00:03:51,500
additional space.

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00:03:51,500 --> 00:03:53,930
The very first question
to ask us in this scenario

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is, how many new networks,
or new subnets, if you will,

83
00:03:58,550 --> 00:04:00,590
do we need to create
for our topology?

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00:04:00,590 --> 00:04:04,610
In this example, we
need 1, 2, and 3.

85
00:04:04,610 --> 00:04:07,670
Step number one, I'd like you
to write this down with me,

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00:04:07,670 --> 00:04:15,360
is identify number of
new subnets needed.

87
00:04:15,360 --> 00:04:18,300
Because that is the
very first step.

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00:04:18,300 --> 00:04:21,000
Identify the number
of new subnets needed.

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00:04:21,000 --> 00:04:22,590
Once you've got
that jotted down,

90
00:04:22,590 --> 00:04:26,160
I'm next going to share with
you how you can calculate

91
00:04:26,160 --> 00:04:28,950
how many bits you need to take.

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00:04:28,950 --> 00:04:30,720
I'm talking about
the stealing bits

93
00:04:30,720 --> 00:04:33,730
from the valid host bits
which are currently available.

94
00:04:33,730 --> 00:04:37,060
And we're going to sacrifice
them to network address space.

95
00:04:37,060 --> 00:04:39,450
And that's done through
something called the finger

96
00:04:39,450 --> 00:04:40,440
game.

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00:04:40,440 --> 00:04:42,960
Now if you're wondering, Keith,
what the heck is the finger

98
00:04:42,960 --> 00:04:44,850
game, you're not going
to have to wonder too

99
00:04:44,850 --> 00:04:47,058
much longer, because we're
going to play it together.

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00:04:47,058 --> 00:04:48,940
I'm going to do this
literally with you.

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00:04:48,940 --> 00:04:50,560
So here's where I'd like to do.

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00:04:50,560 --> 00:04:52,185
I'd like you to look
at your fingers,

103
00:04:52,185 --> 00:04:54,690
and include your thumb
in that discussion.

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00:04:54,690 --> 00:04:55,860
Look at your fingers.

105
00:04:55,860 --> 00:05:00,100
And I'd like you to imagine
that your fingers are bits.

106
00:05:00,100 --> 00:05:01,754
So if you hold up
all your digits

107
00:05:01,754 --> 00:05:04,170
on your right hand or your
left hand and you look at them,

108
00:05:04,170 --> 00:05:05,430
how many digits are there?

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How many bits are there?

110
00:05:06,910 --> 00:05:09,000
And the answer for most
people is going to be 5.

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00:05:09,000 --> 00:05:10,680
Unless you're like my shop
teacher in high school,

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00:05:10,680 --> 00:05:11,850
but that's another story.

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00:05:11,850 --> 00:05:13,920
So let's go ahead and
use the presumption

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that most people are going to
have 5 digits on their hand.

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00:05:17,000 --> 00:05:20,820
And for this game, each of
those digits represents a bit.

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00:05:20,820 --> 00:05:22,330
Here's what I'd like you to do.

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00:05:22,330 --> 00:05:25,392
I'd like you to go ahead and
act like Fonzie from Happy Days.

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00:05:25,392 --> 00:05:26,850
If you don't know
who that is, I'll

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00:05:26,850 --> 00:05:28,050
go ahead and walk
you through this.

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You're going to make a
fist with your right hand,

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00:05:30,270 --> 00:05:32,340
stick it out in front
of you, and then stick

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00:05:32,340 --> 00:05:34,690
just your thumb up in the air.

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With your thumb in
the air, I'd like

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00:05:36,190 --> 00:05:37,920
you to look at the
back of your thumb.

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Look at your thumbnail.

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00:05:39,210 --> 00:05:41,520
I'd like you to
imagine that somebody

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00:05:41,520 --> 00:05:44,400
took a black, permanent
marker and they

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00:05:44,400 --> 00:05:47,580
wrote, right on your
thumbnail, the number 2.

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00:05:47,580 --> 00:05:48,450
So look at it.

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See it.

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00:05:49,280 --> 00:05:50,830
What kind of font did they use?

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Is it clean?

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00:05:51,480 --> 00:05:53,390
Is it a sloppy written 2?

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00:05:53,390 --> 00:05:56,310
But see that 2 on the back
of your thumb, and here's

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00:05:56,310 --> 00:05:57,270
what we're going to do.

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00:05:57,270 --> 00:06:02,130
If you only need 2 new
subnetworks, all you need do

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00:06:02,130 --> 00:06:06,900
is take a single host bit from
the current available host bits

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00:06:06,900 --> 00:06:08,580
to accomplish that.

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00:06:08,580 --> 00:06:10,180
The 2 is on your thumb.

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00:06:10,180 --> 00:06:13,860
Your thumb represents that one
bit, and that's the formula.

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00:06:13,860 --> 00:06:17,346
Now in our case, we need
more than just 2 subnets.

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00:06:17,346 --> 00:06:18,720
So here's what
we're going to do.

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00:06:18,720 --> 00:06:20,880
With your thumbs
still up in the air,

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00:06:20,880 --> 00:06:23,220
we're going to go ahead
and bring up another digit,

145
00:06:23,220 --> 00:06:24,780
like your pointer finger.

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00:06:24,780 --> 00:06:26,760
And when you bring
that finger up,

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I want you to double
the 2 on your thumb.

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00:06:29,700 --> 00:06:31,470
So that goes to 4.

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00:06:31,470 --> 00:06:33,990
The number that
you verbally said

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00:06:33,990 --> 00:06:36,462
is the number of
subnets you can create.

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00:06:36,462 --> 00:06:38,670
If you look at the number
of digits in the air, which

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00:06:38,670 --> 00:06:41,490
are now 2, that's how
many bits it takes

153
00:06:41,490 --> 00:06:43,830
to generate that many subnets.

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00:06:43,830 --> 00:06:45,630
Just for [INAUDIBLE]
that meets our needs.

155
00:06:45,630 --> 00:06:47,820
All we really need
to do is take 2 bits

156
00:06:47,820 --> 00:06:50,850
and that'll create 4 subnets,
which meets our need of 3.

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00:06:50,850 --> 00:06:51,790
So let's do this.

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00:06:51,790 --> 00:06:53,230
Let's start from scratch.

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00:06:53,230 --> 00:06:56,760
And let's see how many
subnets we could create if we

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00:06:56,760 --> 00:06:59,880
stole or took 5 host bits.

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00:06:59,880 --> 00:07:02,130
The game always
starts like Fonzie.

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00:07:02,130 --> 00:07:04,380
You make a fist, you put
your thumb in the air.

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00:07:04,380 --> 00:07:06,406
On the back of your
thumb there's a 2.

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00:07:06,406 --> 00:07:09,030
The next thing we're going to do
is bring up our pointer finger

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00:07:09,030 --> 00:07:12,090
and verbally double
that number, to go to 4.

166
00:07:12,090 --> 00:07:13,540
And bring up another finger.

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00:07:13,540 --> 00:07:17,250
So we have 3 digits in the air
and double the number to 8.

168
00:07:17,250 --> 00:07:18,840
Bring up another digit.

169
00:07:18,840 --> 00:07:20,970
Double the number to 16.

170
00:07:20,970 --> 00:07:22,080
Bring up another digit.

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00:07:22,080 --> 00:07:26,755
Now all 5 digits are up and
double that number to 32.

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00:07:26,755 --> 00:07:29,130
And I want to remind you what
the importance of this game

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00:07:29,130 --> 00:07:30,480
is, what the relevance is.

174
00:07:30,480 --> 00:07:33,810
If you look at your fingers,
you have 5 digits in the air.

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00:07:33,810 --> 00:07:38,490
That means if you take 5 bits
away from the host addresses

176
00:07:38,490 --> 00:07:41,310
and you allocate them
for network addressing,

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00:07:41,310 --> 00:07:45,060
you can have 32
brand new subnets

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00:07:45,060 --> 00:07:48,660
by using the address
space available in those 5

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00:07:48,660 --> 00:07:50,460
reallocated bits.

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00:07:50,460 --> 00:07:52,650
And this finger
game that we can use

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00:07:52,650 --> 00:07:55,680
to calculate the number
of bits or digits

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00:07:55,680 --> 00:07:59,190
on our fingers to use, to create
a certain number of subnets,

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00:07:59,190 --> 00:08:01,860
is a very valuable skill
that will come in very handy

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00:08:01,860 --> 00:08:03,150
for you.

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00:08:03,150 --> 00:08:05,850
In our case we
only need 3 subnets

186
00:08:05,850 --> 00:08:08,820
to support this
topology right here.

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00:08:08,820 --> 00:08:11,340
Just as a review, let's do
the thumb game once again.

188
00:08:11,340 --> 00:08:12,840
And we want to make
sure we're going

189
00:08:12,840 --> 00:08:15,180
to identify how
many bits it takes

190
00:08:15,180 --> 00:08:17,880
to create up to 3 subnets.

191
00:08:17,880 --> 00:08:20,130
So we play the finger
game by making a fist,

192
00:08:20,130 --> 00:08:22,920
we put our thumb in the air,
there's a 2 on our thumb.

193
00:08:22,920 --> 00:08:24,120
2 is not enough.

194
00:08:24,120 --> 00:08:28,110
We bring up another digit, and
we double that number to 4.

195
00:08:28,110 --> 00:08:30,540
And that means, with
2 bits, represented

196
00:08:30,540 --> 00:08:33,270
by the 2 digits that
are up in our hand,

197
00:08:33,270 --> 00:08:35,760
we can create up to 4 subnets.

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00:08:35,760 --> 00:08:43,350
That third step is to identify
number of bits to sacrifice.

199
00:08:43,350 --> 00:08:47,790
And I do say sacrifice, because
they were available host bits.

200
00:08:47,790 --> 00:08:51,480
And once we sacrificed them
over for network addressing,

201
00:08:51,480 --> 00:08:54,700
they will no longer be
available for host bits.

202
00:08:54,700 --> 00:08:58,050
So in our case, we are
going to sacrifice 2 host

203
00:08:58,050 --> 00:09:01,380
bits, because that allows
us to have up to 4 subnets.

204
00:09:01,380 --> 00:09:05,460
1 bit wasn't enough and 2
bits gives us up to 4 subnets,

205
00:09:05,460 --> 00:09:06,870
which meets our need.

206
00:09:06,870 --> 00:09:09,630
And the fourth step, and
this is the most important,

207
00:09:09,630 --> 00:09:14,919
is to go ahead and
let every one know.

208
00:09:14,919 --> 00:09:17,210
What do you mean, Keith, you
have to let everyone know?

209
00:09:17,210 --> 00:09:19,770
You see, if we're going
to change the rules

210
00:09:19,770 --> 00:09:23,430
and use 2 host bits for
the network address,

211
00:09:23,430 --> 00:09:26,010
we need to make sure that all
the devices on the network

212
00:09:26,010 --> 00:09:26,760
know about it.

213
00:09:26,760 --> 00:09:32,360
What we're going to do is,
we're going to modify the mask.

214
00:09:32,360 --> 00:09:34,740
For this network, at
the moment, the mask

215
00:09:34,740 --> 00:09:39,780
is only claiming the first
3 octets, the first 24

216
00:09:39,780 --> 00:09:41,640
bits of the IP address space.

217
00:09:41,640 --> 00:09:44,670
But now, if we're going to
use the additional first 2

218
00:09:44,670 --> 00:09:48,000
bits of that last octet,
we need to change the mask.

219
00:09:48,000 --> 00:09:50,520
And that, my friend,
is how we communicate

220
00:09:50,520 --> 00:09:52,920
the details of using
additional bits

221
00:09:52,920 --> 00:09:54,480
for the purposes of networking.

222
00:09:54,480 --> 00:09:57,870
We're simply going to move
the mask that many bits

223
00:09:57,870 --> 00:10:01,440
to the right, and they're
still going to be contiguous.

224
00:10:01,440 --> 00:10:04,980
Now it's going to be the first
24 bits here, plus the first 2

225
00:10:04,980 --> 00:10:06,360
of this last octet.

226
00:10:06,360 --> 00:10:08,910
The new mask is going to be 26.

227
00:10:08,910 --> 00:10:11,350
Now out of our beautiful
IP address space,

228
00:10:11,350 --> 00:10:14,100
now we only have 6
host bits available

229
00:10:14,100 --> 00:10:17,250
left for host addressing,
which is restricting

230
00:10:17,250 --> 00:10:18,840
us a little bit on that end.

231
00:10:18,840 --> 00:10:21,630
But now we have more
address space to play with,

232
00:10:21,630 --> 00:10:24,660
so we can create up to
4 brand new subnets.

233
00:10:24,660 --> 00:10:29,610
Your exercise right now is to
write out these four steps.

234
00:10:29,610 --> 00:10:31,950
And that is to identify
the number of new subnets

235
00:10:31,950 --> 00:10:34,920
that you need to create,
use the finger game,

236
00:10:34,920 --> 00:10:37,950
with the 2 on your thumb,
with your fingers representing

237
00:10:37,950 --> 00:10:39,889
bits and doubling
the number every time

238
00:10:39,889 --> 00:10:42,180
you bring up a new digit--
remember to start with the 2

239
00:10:42,180 --> 00:10:43,200
on your thumb.

240
00:10:43,200 --> 00:10:45,267
And then once you
calculate how many fingers

241
00:10:45,267 --> 00:10:47,850
are in the air that meets your
requirements for the new number

242
00:10:47,850 --> 00:10:50,190
of subnets, you identify that.

243
00:10:50,190 --> 00:10:52,860
In our example, we only
needed to take 2 bits.

244
00:10:52,860 --> 00:10:55,440
And the fourth step
is to modify the mask

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00:10:55,440 --> 00:10:57,270
to let everybody know about it.

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00:10:57,270 --> 00:10:59,550
And that's moving
the mast to the right

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00:10:59,550 --> 00:11:02,010
by that quantity of bits.

248
00:11:02,010 --> 00:11:03,870
Take a moment,
make sure you have

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00:11:03,870 --> 00:11:06,340
those 4 steps written down.

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00:11:06,340 --> 00:11:08,940
And what I would like you to
do is go ahead and pause me,

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00:11:08,940 --> 00:11:11,370
turn the paper
over, and I'd like

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00:11:11,370 --> 00:11:14,100
you to go ahead and, from
memory, repeat those steps.

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00:11:14,100 --> 00:11:17,340
If need to peek over the
other side as a refresher,

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00:11:17,340 --> 00:11:19,230
that's perfectly fine
in the beginning.

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00:11:19,230 --> 00:11:21,570
But I want to make sure
that you, on your own,

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00:11:21,570 --> 00:11:23,790
know this exact process.

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00:11:23,790 --> 00:11:26,340
When you've written these out,
and are comfortable that you

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00:11:26,340 --> 00:11:28,980
understand the process
that you should go through,

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00:11:28,980 --> 00:11:30,690
go ahead and resume me.

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00:11:30,690 --> 00:11:32,790
And I will share with
you one more technique

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00:11:32,790 --> 00:11:34,290
that's really
important regarding

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00:11:34,290 --> 00:11:37,834
the moving of that mask,
those 2 additional bits.

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00:11:37,834 --> 00:11:40,500
Now here's one of the challenges
that's going to come up when we

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00:11:40,500 --> 00:11:45,090
move that mask from a /24,
which it was, over to a /26,

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00:11:45,090 --> 00:11:48,810
is that how do we actually
represent that in decimal?

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00:11:48,810 --> 00:11:50,970
Because when we work
with IP addresses,

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00:11:50,970 --> 00:11:52,770
we're putting in data decimal.

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00:11:52,770 --> 00:11:55,810
So what does a /26 look
like in data decimal?

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00:11:55,810 --> 00:12:01,530
Well, the first 24 bits are good
for the mask, or 255.255.255.

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00:12:01,530 --> 00:12:02,620
Now, that's not new.

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00:12:02,620 --> 00:12:06,540
What is new is, how do
we represent the first 2

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00:12:06,540 --> 00:12:10,650
bits of that last
octet, these guys

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00:12:10,650 --> 00:12:13,390
right here, for the
mask that they are on?

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00:12:13,390 --> 00:12:16,890
And the answer is, we're going
to go back to binary for that.

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This bit on and this bit on.

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00:12:18,910 --> 00:12:21,960
So that's bit 25 and bit 26.

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00:12:21,960 --> 00:12:24,960
And all these bits in
the mask are now off.

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00:12:24,960 --> 00:12:26,537
What would that be in decimal?

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00:12:26,537 --> 00:12:28,620
Because that's how we're
going to have to input it

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00:12:28,620 --> 00:12:30,453
to the device we're
working on, whether it's

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00:12:30,453 --> 00:12:31,590
a router or a computer.

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00:12:31,590 --> 00:12:33,120
And to figure this
out, we already

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00:12:33,120 --> 00:12:36,090
know how to do the conversion
from binary to decimal.

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00:12:36,090 --> 00:12:38,190
We simply add the values.

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00:12:38,190 --> 00:12:44,430
We add 128 and 64, and that's
a whopping total of 192.

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00:12:44,430 --> 00:12:48,090
So for the mask in the last
octet, we would put 192.

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00:12:48,090 --> 00:12:50,370
And what that tells the
router or the computer that

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00:12:50,370 --> 00:12:54,810
you're on is that, hey,
we're using a /26 bit mask.

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00:12:54,810 --> 00:12:58,500
The first 3 octets are all
taken for network addressing,

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00:12:58,500 --> 00:13:01,050
and the first two bits
of that last octet

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00:13:01,050 --> 00:13:03,810
are also taken for
network addressing.

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00:13:03,810 --> 00:13:05,340
Now I can hear it already.

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00:13:05,340 --> 00:13:07,320
Some of you might
be saying, oh, I

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00:13:07,320 --> 00:13:10,530
don't want to have to convert
from binary into decimal

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00:13:10,530 --> 00:13:12,180
every single time
I put some type

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00:13:12,180 --> 00:13:16,350
of a custom or non-default
mask on an IP address.

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00:13:16,350 --> 00:13:17,820
And I'm totally with you.

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00:13:17,820 --> 00:13:19,920
And that's why what I
would recommend you do

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00:13:19,920 --> 00:13:23,340
is create this mask
values table, as well.

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00:13:23,340 --> 00:13:26,010
Right when you sit down to
start working with IP version

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00:13:26,010 --> 00:13:28,650
4 subnetting, you should
definitely write out this table

302
00:13:28,650 --> 00:13:31,800
right here, which is the
weights of the various positions

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00:13:31,800 --> 00:13:33,850
for one byte of data.

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00:13:33,850 --> 00:13:36,210
And you should also jot
down the mask values

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00:13:36,210 --> 00:13:37,620
for each of those positions.

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00:13:37,620 --> 00:13:40,560
For example, if we had a
bit on in this position

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00:13:40,560 --> 00:13:44,200
by itself and nothing else,
that would be a value of 128.

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00:13:44,200 --> 00:13:47,250
If we take 128 plus 64,
that'd be 2 bits on,

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00:13:47,250 --> 00:13:49,320
it'd be a total of 192.

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00:13:49,320 --> 00:13:51,460
If we had the first 3
bits on, for example,

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00:13:51,460 --> 00:13:56,160
it'd be 128 plus 64
plus 32, which is 224.

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00:13:56,160 --> 00:13:58,230
And plus 16 more would be 240.

313
00:13:58,230 --> 00:13:59,880
And plus 8 more be 248.

314
00:13:59,880 --> 00:14:02,040
Plus 4 more be 252.

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00:14:02,040 --> 00:14:04,560
At some point, if you work
with IP version 4 a lot,

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00:14:04,560 --> 00:14:07,810
you're going to have these
values up here absolutely

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00:14:07,810 --> 00:14:08,460
memorized.

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00:14:08,460 --> 00:14:10,890
But until then what
you could do is this.

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00:14:10,890 --> 00:14:13,340
Simply write out this table.

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00:14:13,340 --> 00:14:15,280
Write the weights
first, and then

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00:14:15,280 --> 00:14:17,160
simply write the mask values.

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00:14:17,160 --> 00:14:21,550
The mask values are going to be
128, plus 64, plus 32, plus 16,

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00:14:21,550 --> 00:14:23,460
and that's that
top row right here.

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00:14:23,460 --> 00:14:25,440
If we had a situation
where we needed

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00:14:25,440 --> 00:14:28,860
to use 5 bits for
custom subnetting,

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00:14:28,860 --> 00:14:32,250
because we had a requirement
for 32 sub networks,

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00:14:32,250 --> 00:14:34,650
and we needed to take
5 additional bits,

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00:14:34,650 --> 00:14:36,289
it would look like
this in binary.

329
00:14:36,289 --> 00:14:38,830
We take that one, that one, that
one, that one, and that one.

330
00:14:38,830 --> 00:14:41,850
We would leave these last
3 bits for host addressing.

331
00:14:41,850 --> 00:14:46,380
The dividing line would be right
here and our mask value be 248.

332
00:14:46,380 --> 00:14:48,900
And if we needed to, you
could manually calculate that.

333
00:14:48,900 --> 00:14:52,410
128 plus 64 plus
32 plus 16 plus 8.

334
00:14:52,410 --> 00:14:55,920
But having this table
here is very, very handy.

335
00:14:55,920 --> 00:14:57,750
Here are the 2 things
that I want you

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00:14:57,750 --> 00:14:59,650
to take away from this video.

337
00:14:59,650 --> 00:15:03,480
Number 1, I want you to be
comfortable with the idea

338
00:15:03,480 --> 00:15:06,100
that we are stealing,
we are taking away,

339
00:15:06,100 --> 00:15:09,360
available host bits
and sacrificing them

340
00:15:09,360 --> 00:15:12,030
for the purpose of creating
additional networks.

341
00:15:12,030 --> 00:15:14,488
The other thing I want to make
sure you're comfortable with

342
00:15:14,488 --> 00:15:15,220
is quantity.

343
00:15:15,220 --> 00:15:18,180
How many bits do we
need to take in order

344
00:15:18,180 --> 00:15:20,160
to create a certain
number of subnets?

345
00:15:20,160 --> 00:15:23,940
And that's all about
using the finger game.

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00:15:23,940 --> 00:15:26,220
I hope this has been
informative for you,

347
00:15:26,220 --> 00:15:28,910
and I'd like to thank
you for viewing.

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00:15:28,910 --> 00:15:29,478