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>> It's our second flavor of subnetting now.
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Subnets based on host requirements
rather than network requirements
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as we did in the previous nugget.
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So, just like the previous nugget we're jumping
straight in the water with four unique examples.
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Now, this first example looks
the same and feels the same
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as the first example we saw in the last nugget.
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However, there's a major twist
to it that makes it different.
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Notice, this organization has purchased
the Class C address 216.21.5.0.
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So, immediately I think slash 24.
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That's the Class C subnet app.
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And we'd like to create networks
of thirty hosts each.
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Ding ding ding ding.
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That's the unique twist.
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So, in the previous nugget, we said,
how many networks do we want for this?
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And we counted them.
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OK. One network, two networks,
three networks, four and five.
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And so we figured this question
based on five networks and kind
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of broke up the subnets within each one.
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Now, this one we've stated the
question a little differently.
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We said, well, honestly I'm not, I don't
really, my main focus, let me put it that way,
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my main focus is not on how
many networks I can get.
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My main focus is that I need networks of thirty
hosts each because my office is, you know,
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that office has twenty people, that
office has twenty eight people,
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that one has fifteen people, so I really
want to create this so it fits my offices.
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So, the offices will have 30 usable IP
addresses that they can use per office.
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The good news is that the process is almost
exactly the same as it was previously.
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So, let me quantify almost.
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So, first I've written up
our number again up here.
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216.21.5.0 is the network and
we wanted 30 hosts per network.
30
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Right? So, 30 hosts per network.
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So, step one is determine the number
of hosts and convert to binary.
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So, we started with 30 hosts and
we'll write that as a binary number.
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Now this is the same as it was previously,
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it's just it said convert the
number of networks to binary 4 2 1.
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So, we'll do thirty, so that'll be 0 0 0 1, so
30 minus 16 and I know, there's the shortcut,
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but we're going to do it the
long way to start off with.
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4, 14 so 1 minus equals 8,
so that'd be six, right?
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1 1 0, so the binary equivalent
of 30 is 00011110, good.
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OK. Step 2.
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Reserve bits in the subnet
mask and find your increment.
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Now, we're back to that Class C network,
255.255.255.255.0 So, I'll go, 1,2,3,4,5,6,7,8.
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1,2,3,4,5,6,7,8.
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1,2,3,4,5,6,7,8.
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1,2,3,4,5,6,7,8.
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Good. Now, here's where the twist comes
in, here's where the almost comes in.
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Now, previously, I kept asking the
question, OK, are we after networks
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or are we after hosts per network?
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And the answer in the previous
nugget was always networks.
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We're after networks, networks, networks.
50
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We kept emphasizing we're after networks.
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And network bits were the ones, right?
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We were saying ok well then lets put ones
here and lets stretch it out this way.
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Now that all changes now,
because instead of saying I'm
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after networks, I'm after hosts per network.
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Now, keep in mind, I'm still subnetting,
it's not like I'm moving those ones backwards
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or anything like that, I'm still subnetting.
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However, my focus, my main focus
is not how many networks I get,
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it's how many hosts per network I get.
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So, what I'm going to be doing is
saying, instead of looking for, you know,
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and we've got to identify, it takes five
bits to get the number thirty, right?
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Just like we saw in the previous nugget, so
instead of saying I need five network bits,
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because that would be the previous style,
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is saying I've got 30 networks
that I'm after, no no no no.
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I'm saying, I can't get the number
30 with any less than five bits,
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so I need to save five host bits.
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1, 2, 3, 4, 5.
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Did you notice what I did there?
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Two things: one is save the five host bits.
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But, also did you notice
the direction I was going?
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Instead of going left to right, like I did
with the networks, I went right to left.
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Because that's where my zeros exist.
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That's where the client bits are at.
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So, I'm saying, as long as I have five
bits, I know that I can get the number 30.
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OK? All the other ones I
don't need for the clients.
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I've met my requirements.
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I can get my 30 hosts with my five bits.
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So, the rest of them can go to the
network site because guess what?
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I'm still subnetting, right?
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This is still subnetting, I'm still
breaking one network which was 216.21.5,
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into multiple subnetworks, but I just
wanted to make sure that those subnetworks,
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however many I get, will have at
least 30 hosts per subnetwork, right?
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OK. Everything else is the same.
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That's the story, is my focus is on the zeros,
so now let's figure the rest of this out.
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It says, so we've changed our subnet mask, we
know what it's going to be; it's 255.255.255
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and then this is the lest octet,
so it'd be 128 plus 64 plus 32.
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00:05:57,866 --> 00:06:06,696
That'd be 224, or if we're using citer notation,
we just moved from a slash 24 down to a,
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we added 3 more, so that'll be a slash 27.
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Again, just, these are two ways
of writing the subnet mask.
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That's it.
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No other concepts than that.
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Now, the increment is still the
lowest network bit converted back
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to a decimal number; that would be 32.
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Right? Lowest network bit is the decimal, and
by the way, when we're figuring out the number
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of hosts, if this number is ever
less than your host, be concerned,
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because that really defines the ranges.
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How big are they?
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So now, I can come down here to
figure out my network ranges.
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216.21.5.0 is where we begin, and then we just
start adding our increment of the third octet.
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You see how everything else is the same?
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216.21.5.32 216.21.5.64 and
down and down we go: 96, 128,
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and this would continue on down off the screen.
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Fill in the end ranges.
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This goes to 216.21.5.
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what's the last IP address?
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31, right?
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216 also realizing that we can't
use that broadcast address because,
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well because the last idea,
because it's a broadcast,
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so usable, we actually have 1 through 30.
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We have exactly 30 usable hosts per subnet.
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Just one of those weird values that
happened to land on the exact amount,
111
00:07:51,966 --> 00:07:56,786
but we would just continue this trend all
the way down, filling in the network ranges.
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00:07:56,786 --> 00:08:01,276
Awesome. So, again, the slight tweak that
we get is right here in the second step,
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to where we're no longer
focused primarily on adding ones.
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We're focused on saving zeros.
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I was teaching a class one time, and we
were trying to figure out if this was long,
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like when I had first created the
subnetting method, and we were trying to,
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and somebody was like, how do I remember that?
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You know, how do I remember when I'm going right
to left or left to right and ones and zeros
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and I was like, I don't know, how can
we remember, guys, to save the host bits
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and this guy from the back, he was totally
random, he yells out, save the hosts!
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And we all kind of looked
at him, we were like, what?
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And he goes, well it's kind of like, you know
save the whales, you know, like save, you know,
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we have to save the hosts, so that
became like the theme from there on out,
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is any time we saw one of these
examples, it was like, ok,
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are we trying to add more
networks or save the hosts?
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And everyone would yell out, save the hosts!
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So, I have been teaching in classrooms
for a long time the subnet method,
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and it was funny because my wife, my wife
actualy went to one of my CCNA classes early on,
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so I can say she's a CCNA sort of,
just cause she attended the class.
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And, so I took her with me to Cisco networkers;
this was maybe 5 years ago, it was before kids,
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bc, when we could do that, and so we were
there and she was at this big event with me,
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and we were, just a ton of people just crowds
and crowds of network people at networkers
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and there was a guy who from across
the room goes, save the hosts!
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And it was funny, my wife looks at me and
she goes, someone did not just say that?
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And I was like, where is he?
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My brother, you know and so it was
funny, we searched and I was like hey!
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And it was just a guy that had been
in one of my classes so anyway,
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this save the hosts thing has been around
for a long time so I'm going to use it.
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I'm going to keep saying that when
we're going through these examples.
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OK. Example number 2.
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We've got a Class C address again,
same story, 195.5.20.0 and we're going
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to need 50 hosts per network,
so a little larger organization
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of 50 hosts per network is
what we're after, so let's go.
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00:09:46,026 --> 00:09:46,926
I've got 50 is my magic number.
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00:09:46,956 --> 00:09:48,366
I'm looking for how many
bits to get the number 50?
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64, 32, 16, 8, 4, 2, 1.
147
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So, I'm going to go no, no, yes.
148
00:09:50,376 --> 00:09:52,506
Now, I'm going to start invoking shortcut
number one right here, I'm going to say ok,
149
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I can stop because now I know it gets, excuse
me, it takes six bits to get the number 50.
150
00:09:55,056 --> 00:09:55,626
That's an easy one, right?
151
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That's 48, 50, but nonetheless, it still
takes 50 bits to get to 150, so now I look,
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it's a Class C, so let's
do this, I'll do slash 24.
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And again I'll start showing you
now we've seen a few of these.
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Let me give you some shortcuts that I do
when I'm writing it on paper, like on a test
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or something like that, what
I'll do is I'll say ok, slash 24.
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I know that's 24 ones.
157
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I know that's the first three octets,
158
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so when I'm used to saying it,
I'll go 111....111.00000000.
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I always write the zeros.
160
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Zero. Because that's our playground,
that's where we get to work.
161
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So, essentially, again, if this
messes you up, don't do it.
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00:10:32,526 --> 00:10:36,636
But that's what I do, just so I
don't have to write all three octets.
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This is, this represents 24 bits.
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Right? 24 ones split between the
first three octets of the subnet mask.
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So, what I'm focused on is the zeros.
166
00:10:46,846 --> 00:10:48,666
Now, again, back to my scenario.
167
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Are we creating 50 networks or are
we saving 50 hosts per network?
168
00:10:53,306 --> 00:10:56,026
Save the hosts we all yell, hands in the air.
169
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So, we're going to focus
instead on saving six bits.
170
00:11:00,286 --> 00:11:09,106
1,2,3,4,5,6 must remain zero because I can't get
my fifty hosts with any less than that and then,
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shup shupe, those two can flip over to
one, because I'm still doing my subnetting.
172
00:11:12,506 --> 00:11:15,186
So, now I've got my new subnet mask.
173
00:11:15,186 --> 00:11:25,576
It moves to a slash 26, or if I wanted to write
that in decimal it would be 255.255.255.192.
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00:11:25,616 --> 00:11:29,846
That'd be 128 plus 64, right?
175
00:11:29,846 --> 00:11:33,786
So, the lowest network bit, converted
back to a decimal is 64 in this case,
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00:11:33,786 --> 00:11:38,546
which makes me feel warm and fuzzy because
I'm looking, ok, I needed 50, I got 64, right?
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00:11:38,936 --> 00:11:44,926
So, I'm going to come down here
and let's use that increment, 195.
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00:11:45,506 --> 00:11:46,746
Oh and be so careful.
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00:11:47,096 --> 00:11:51,996
I've seen on Cisco exam, I don't know
why Cisco does this, but, for instance,
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00:11:51,996 --> 00:11:58,186
everybody's used to a private IP address,
like 192.168.1.0 and all those kind of things.
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00:11:58,456 --> 00:12:01,766
Cisco will have a simulation on
their exam where they're like, ok,
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00:12:01,766 --> 00:12:07,916
go ahead and assign the IP address
192.186.1.9 to that interface.
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00:12:07,916 --> 00:12:13,296
I don't know why they do that, because it's
so, like you see that and you're so used
184
00:12:13,296 --> 00:12:17,306
to seeing this that you automatically
transpose them when you type
185
00:12:17,636 --> 00:12:20,446
and then you assign the wrong
address, but maybe they're just like,
186
00:12:20,446 --> 00:12:22,356
we want to make sure you're
really reading the question.
187
00:12:22,356 --> 00:12:27,196
But nonetheless, 195.5.20.0
is where we're beginning.
188
00:12:27,196 --> 00:12:32,846
It's in the fourth octet, so
I'm going to do 195.5.20.64.
189
00:12:32,916 --> 00:12:34,576
I'm going to take this one all the way.
190
00:12:34,576 --> 00:12:38,426
195.5.20.128.
191
00:12:38,606 --> 00:12:42,036
.192. Now, what happens if we add 64 to 192?
192
00:12:42,036 --> 00:12:43,856
We get 256.
193
00:12:44,166 --> 00:12:46,376
Again, just like the last nugget, don't panic,
194
00:12:46,376 --> 00:12:48,846
it's ok that you missed it,
that means you're done.
195
00:12:48,846 --> 00:12:50,546
So, I'm going to fill in the in-ranges.
196
00:12:50,546 --> 00:12:51,846
This goes to 63.
197
00:12:51,966 --> 00:12:55,646
127. 191. 255.
198
00:12:56,806 --> 00:12:57,896
So, what does this tell me?
199
00:12:58,296 --> 00:13:04,106
This tells me that when I'm getting
networks of at least 50 hosts per network,
200
00:13:04,106 --> 00:13:07,336
I can only get 4 networks
out of a Class C block.
201
00:13:07,336 --> 00:13:12,676
I just simply run out of IP addresses if I
try to go more than that, so that's good,
202
00:13:12,676 --> 00:13:15,746
it meets my requirement and it also gives
us a chance to go back to that formula.
203
00:13:15,746 --> 00:13:16,216
Remember that?
204
00:13:16,436 --> 00:13:18,146
Two to the power of bits.
205
00:13:18,146 --> 00:13:22,166
So, I'll say, if I'm curious about the
networks, I'll do two to the power of two
206
00:13:22,166 --> 00:13:24,656
because there's two network
bits, so that's two times two
207
00:13:24,656 --> 00:13:26,586
or remember these guys to the power of zero.
208
00:13:26,586 --> 00:13:30,376
1,2,3,4,5,6.
209
00:13:30,376 --> 00:13:32,826
So, I can say two to the
power of two is actually four.
210
00:13:32,826 --> 00:13:34,636
So, I get four networks and that lines up.
211
00:13:34,846 --> 00:13:37,496
Or, if I'm saying, well how
many hosts do I really get?
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00:13:37,746 --> 00:13:40,756
I can do two to the power of,
well we got six host bits.
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00:13:41,006 --> 00:13:42,056
So, look up here, 6.
214
00:13:42,056 --> 00:13:43,456
So, that'd be 64.
215
00:13:45,076 --> 00:13:49,846
But, I always have to subtract two,
so I actually get 62 usable hosts,
216
00:13:49,846 --> 00:13:53,636
because I've got to account for the
broadcasting network per network.
217
00:13:53,636 --> 00:13:57,556
Yes, it's more than 50 but that's
just how the binary works out.
218
00:13:57,556 --> 00:14:03,026
There's no binary increment, you know
that, the next one down would be 32.
219
00:14:03,226 --> 00:14:05,846
Do you kind of see how these numbers just seem
220
00:14:05,846 --> 00:14:08,246
to repeat themselves again
and again we see them.
221
00:14:08,436 --> 00:14:12,976
And that's how you can get so comfortable with
networking and so comfortable with subnetting,
222
00:14:13,216 --> 00:14:17,066
is once you get used to seeing those eight
values, you just kind of see them used
223
00:14:17,066 --> 00:14:18,516
and popping up in different places.
224
00:14:19,806 --> 00:14:21,046
Alright, third example.
225
00:14:21,046 --> 00:14:29,776
Let's go beyond the class c. We've got
150.5.0.0 and we want 500 hosts per network.
226
00:14:29,776 --> 00:14:32,416
That's the biggest one that I
would suggest you would create.
227
00:14:32,676 --> 00:14:34,616
Otherwise broadcasts get a little crazy.
228
00:14:34,616 --> 00:14:35,766
So, let's do it.
229
00:14:35,856 --> 00:14:36,916
We've got 500.
230
00:14:37,326 --> 00:14:39,026
How many bits to get the number 500?
231
00:14:39,446 --> 00:14:44,496
Well, let's write it up,
128, 64, 32, 16, 8 4, 2,
232
00:14:44,496 --> 00:14:46,906
1 and immediately realize
these as I'm writing this.
233
00:14:47,106 --> 00:14:55,306
We need more digits, we need more binary
values because we can only get 255 with 8 bits.
234
00:14:55,306 --> 00:14:56,536
So we multiply by 2.
235
00:14:56,536 --> 00:15:01,526
We go, ok, 256, 512, 1020, sorry
I'm going a little bit far,
236
00:15:01,526 --> 00:15:03,886
but the point is, we go OK, there.
237
00:15:04,556 --> 00:15:08,986
That's where our first one goes
because I can't subtract 512 from 500,
238
00:15:08,986 --> 00:15:13,346
so if my first one goes right there, again I
could find the whole binary value, but instead,
239
00:15:13,566 --> 00:15:19,356
I look and I go, well to get
the number 500, it takes 9 bits.
240
00:15:20,576 --> 00:15:24,746
I write my original subnet mask which is
slash 16, and again I could use the shortcut,
241
00:15:24,746 --> 00:15:26,236
but I'm going to write it all out this time.
242
00:15:27,296 --> 00:15:33,626
1,2,3,4,5,6,7,8.
243
00:15:34,016 --> 00:15:39,006
1,2,3,4,5,6,7,8.
244
00:15:39,006 --> 00:15:42,786
And 1,2,3,4,5,6,7,8.
245
00:15:42,786 --> 00:15:49,286
I find just when we go to Class B, Class C, I
just like seeing the whole thing right there.
246
00:15:49,286 --> 00:15:55,156
Ok, so, now again, I'm asking the
question, am I creating more networks?
247
00:15:55,156 --> 00:15:58,246
Meaning focus on one, or am I saving the hosts?
248
00:15:58,246 --> 00:15:59,926
Save the hosts, we all yell.
249
00:16:00,016 --> 00:16:08,666
We've got to save 9 host bits, because we can't
get the number 9 with any less than nine bits.
250
00:16:08,666 --> 00:16:15,256
It's like, we can't get the number
500 with any less than 9 bits,
251
00:16:15,256 --> 00:16:24,856
so I'm going to go right
to left, 1,2,3,4,5,6,7,8.9.
252
00:16:24,966 --> 00:16:27,486
Those 9 stay on the host side.
253
00:16:27,586 --> 00:16:29,236
The rest of them, chup, chup, chup, chup.
254
00:16:29,236 --> 00:16:30,086
Is that seven?
255
00:16:30,086 --> 00:16:32,266
Seven. Flip over to the network side.
256
00:16:32,266 --> 00:16:42,486
So all my new subnet masks becomes
a slash 23, which is 16 plus more.
257
00:16:42,486 --> 00:16:51,666
Or, if I was writing in decimal, 255.255.254.0.
258
00:16:51,666 --> 00:16:55,566
That there, those two are just
different forms of the same subnet mask.
259
00:16:55,566 --> 00:16:59,086
My increment is going to be
that guy, who is a q, right?
260
00:16:59,276 --> 00:17:03,346
Yes, he's in the same octet, but remember
each octet restarts the same increment,
261
00:17:03,346 --> 00:17:04,106
so he is a two.
262
00:17:04,106 --> 00:17:04,756
That's fine.
263
00:17:04,896 --> 00:17:07,956
So, now I can use that increment
to find my network ranges.
264
00:17:07,956 --> 00:17:10,936
150.5.0.0.
265
00:17:10,936 --> 00:17:20,406
We go .5.2.0 .5.4.0 .5.6.0 and
down and down and down we go.
266
00:17:20,656 --> 00:17:22,286
Right? Now again, same trick as the last nugget.
267
00:17:22,286 --> 00:17:24,336
We don't want to take this through 1.0.
268
00:17:24,336 --> 00:17:30,836
We want to go 150.5.1.255.
269
00:17:30,836 --> 00:17:36,246
150.5.3.255.
270
00:17:36,246 --> 00:17:40,756
Right? Last IP address before
4.0 and down and down we go.
271
00:17:41,186 --> 00:17:45,836
Now, interesting enough, you might be asked,
272
00:17:45,836 --> 00:17:51,146
well how many hosts per network
does that really give you?
273
00:17:51,146 --> 00:17:58,326
Well, we look at our formula, we say, well
that would be two to the power of nine
274
00:17:58,326 --> 00:18:04,626
because I've got nine host bits minus
two, because we've got to account
275
00:18:04,626 --> 00:18:08,296
for the first and last IP address.
276
00:18:08,296 --> 00:18:15,366
So, I'll just look at this and go,
ok this is two to the power of zero.
277
00:18:15,366 --> 00:18:19,216
1,2,3,4,5,6, 7, 8, 9.
278
00:18:19,306 --> 00:18:25,636
Nine. 512 minus two equals 510 host
bits, or hosts that I get per network.
279
00:18:25,636 --> 00:18:29,626
And it's almost a perfect match
for what I was looking for.
280
00:18:29,626 --> 00:18:30,646
OK. Last example.
281
00:18:30,646 --> 00:18:33,396
We've got the ten network, Class
A network that we want to break
282
00:18:33,396 --> 00:18:35,976
into subnets of 100 hosts per network.
283
00:18:36,116 --> 00:18:40,576
And that's a big network to divide
up into all these little ones.
284
00:18:40,576 --> 00:18:45,206
So, first thing to do is take
that 100 hosts, the hosts- Oh.
285
00:18:45,206 --> 00:18:48,206
A little copy paste madness on
Jeremy, got caught up to him.
286
00:18:48,206 --> 00:18:49,016
This should be hosts.
287
00:18:49,016 --> 00:18:50,806
Hopefully the previous ones weren't like that.
288
00:18:50,806 --> 00:18:54,576
If so, I'm sure you would have seen
a little bubble because I'll go back
289
00:18:54,576 --> 00:18:57,086
and add a bubble there saying,
I really meant hosts.
290
00:18:57,086 --> 00:19:02,606
So, determine the number of
hosts and convert that to binary.
291
00:19:02,606 --> 00:19:08,706
So, I've got 100 hosts that I'm
going to convert to a binary number.
292
00:19:09,106 --> 00:19:14,396
128, 64, 32, 16, 8, 4, 2, 1.
293
00:19:14,396 --> 00:19:20,216
And by the way, the more and more you do
of these, the more you'll get to the point
294
00:19:20,216 --> 00:19:21,806
where you just kind of look at them.
295
00:19:21,916 --> 00:19:25,226
You kind of, I mean, again,
remember, it's eight numbers.
296
00:19:25,226 --> 00:19:27,666
It can only be one of eight numbers, so
when you see 100, you may get to a point
297
00:19:27,696 --> 00:19:28,926
where you don't even have
to write that up anymore.
298
00:19:28,956 --> 00:19:30,516
You just look at it and go,
OK, well that takes 7 bits.
299
00:19:30,546 --> 00:19:33,276
I know that 128 is the eighths bit, so it's
going to take seven bits to do that, so again,
300
00:19:33,306 --> 00:19:34,926
you'll just get faster and faster
and faster at these, as you go.
301
00:19:34,956 --> 00:19:36,186
Just to give you a good guestimate for doing it.
302
00:19:36,216 --> 00:19:38,196
I would suggest before you take the CCNA
exam, that you should be able to work
303
00:19:38,226 --> 00:19:39,186
through one of these guys in five minutes.
304
00:19:39,216 --> 00:19:41,286
I know, I know that's aggressive, but five
minutes I think should be the maximum amount
305
00:19:41,316 --> 00:19:42,876
of time that you spend on doing
an entire question like this.
306
00:19:42,906 --> 00:19:44,286
That's kind of the speed
level that you need to be at.
307
00:19:44,316 --> 00:19:45,516
Otherwise you might run short on your CCNA exam.
308
00:19:45,546 --> 00:19:46,596
So, we've got seven bits that we're getting.
309
00:19:46,626 --> 00:19:48,066
Reserve bits in the mask, so
I'm going to say a slash eight,
310
00:19:48,096 --> 00:19:50,496
that's a Class A, is 1,2,3,4,5,6,7,8 dot.
311
00:19:50,526 --> 00:19:51,636
And then you want to write out all the zeros.
312
00:19:51,666 --> 00:19:53,436
1,2,3,4,5,6,7,8.
313
00:19:53,466 --> 00:19:56,946
1,2,3,4,5,6,7,8 because you've got to be able
to see where these lines are being drawn.
314
00:19:56,976 --> 00:19:58,176
OK, so are we creating 100 networks?
315
00:19:58,206 --> 00:19:58,626
Is that type 1?
316
00:19:58,656 --> 00:19:59,976
Or are we creating 100 hosts per network.
317
00:20:00,106 --> 00:20:03,146
We're at hosts per network, so
save the hosts, save the host bits.
318
00:20:03,146 --> 00:20:09,556
We're going 1,2,3,4,5,6,7, and then 1.
319
00:20:09,556 --> 00:20:10,726
He flips over to the network side.
320
00:20:10,726 --> 00:20:16,626
Now, whoa, what about all the rest of them?
321
00:20:16,626 --> 00:20:17,716
They all flip.
322
00:20:17,716 --> 00:20:19,836
That's my very fast writing.
323
00:20:20,016 --> 00:20:23,606
They all flip over to the network
side because we graduate ourselves
324
00:20:23,606 --> 00:20:28,496
from a slash eight all the way down to a
slash 25, as in all these become subnets.
325
00:20:28,496 --> 00:20:31,796
So, what we get is we get fairly small networks,
326
00:20:31,796 --> 00:20:35,046
100 hosts per network, and
a whole bunch of them.
327
00:20:35,046 --> 00:20:36,786
You know, a whole bunch of these bits.
328
00:20:36,936 --> 00:20:39,466
We say, well good grief, that would be, what?
329
00:20:39,466 --> 00:20:43,316
Two to the power of, we added 8, 16, 17.
330
00:20:43,316 --> 00:20:46,106
17 subnet bits to figure
out the number of subnets.
331
00:20:46,246 --> 00:20:49,726
Are we going to figure that out with- First off,
they're not going to ask you that on the exam.
332
00:20:49,726 --> 00:20:54,756
Cisco is not cruel, often, to
ask you a question like that.
333
00:20:54,756 --> 00:20:59,776
What they'll do is they will,
they'll ask you something
334
00:20:59,776 --> 00:21:01,796
that you can figure out just by multiplication.
335
00:21:01,796 --> 00:21:05,676
What I would do if I got this,
is let's go to scientific.
336
00:21:05,766 --> 00:21:06,476
Yeah, there we go.
337
00:21:06,766 --> 00:21:17,086
So, we can actually do two to the power,
that's x carrot y, 17 equals 131,072 subnets.
338
00:21:17,596 --> 00:21:20,726
So, what this little scheme gives us.
339
00:21:20,726 --> 00:21:23,856
So, we've got a lot of networks
that we can grow into.
340
00:21:23,856 --> 00:21:27,256
So, we go, ok, that's good,
we've got our subnet mask
341
00:21:27,256 --> 00:21:31,786
if we want the decimal version
it's 255.255.255 dot.
342
00:21:31,786 --> 00:21:32,406
what's that last one?
343
00:21:32,406 --> 00:21:33,876
128. That's a new one.
344
00:21:33,876 --> 00:21:34,796
We haven't seen that one yet.
345
00:21:35,356 --> 00:21:38,126
So, those are two different
ways of writing our subnet mask.
346
00:21:38,126 --> 00:21:41,106
Our increment happens to be 128 as well.
347
00:21:41,516 --> 00:21:44,296
Same value as the subnet mask.
348
00:21:44,296 --> 00:21:45,946
It's one of those rare circumstances.
349
00:21:45,946 --> 00:21:49,286
So, now I can drop down and
figure out my incremements.
350
00:21:49,656 --> 00:21:53,726
10.0.0.0 is what I was given,
that's where I began.
351
00:21:53,976 --> 00:21:56,896
My increment is in that last octet, right?
352
00:21:56,896 --> 00:22:00,326
So it's going to go 10.0.0.128.
353
00:22:01,136 --> 00:22:03,336
10.0.0 dot.
354
00:22:03,336 --> 00:22:05,576
Now what if we add 128 to 128?
355
00:22:05,676 --> 00:22:07,566
We get 256, right?
356
00:22:08,016 --> 00:22:09,086
No, we can't have that.
357
00:22:09,426 --> 00:22:11,906
So, this goes back under
one of those rare rules.
358
00:22:12,186 --> 00:22:13,656
I shouldn't say rare.
359
00:22:13,656 --> 00:22:16,006
One of those rules to where,
let me fill in the n ranges.
360
00:22:16,006 --> 00:22:21,186
This goes to 127 and if this was 256
down here, this would go to the 255.
361
00:22:21,436 --> 00:22:24,276
So I just have to say, OK well
the next one then starts at 1.0.
362
00:22:24,276 --> 00:22:29,636
1.128 and then 2.0 and then 2.128.
363
00:22:29,636 --> 00:22:33,536
And it just keeps on going down and down
and fill in the n ranges, this goes to 127,
364
00:22:33,576 --> 00:22:36,116
this goes to 255, do you see the trend?
365
00:22:36,116 --> 00:22:43,796
So, I needed 100 hosts per network and I
ended up getting about 126 hosts per network.
366
00:22:43,796 --> 00:22:49,186
So, our, you know, essentially two to the
power of seven minus two gives us the number
367
00:22:49,186 --> 00:22:51,916
of hosts per network, and that
will give us our network ranges.
368
00:22:52,916 --> 00:22:58,406
Now of course I have homework that I have the
written answers to, where you can download them
369
00:22:58,406 --> 00:23:02,966
from CBT nuggets and get the answers to,
but let me just make a broad statement.
370
00:23:03,016 --> 00:23:05,106
This is what I would like you to do as homework.
371
00:23:05,396 --> 00:23:07,066
Let me make a broad statement.
372
00:23:07,066 --> 00:23:12,356
At this point, I would hope that you're
feeling pretty, pretty warm and fuzzy
373
00:23:12,356 --> 00:23:16,226
about the two different styles of
subnetting that we've talked about so far.
374
00:23:16,556 --> 00:23:19,516
And I say that because, really, it's one style.
375
00:23:19,676 --> 00:23:21,866
It's kind of the same three steps.
376
00:23:21,866 --> 00:23:25,596
I'm just slightly tweaking it as we're getting
into this nugget, and just giving you a number
377
00:23:25,596 --> 00:23:27,286
of examples that we've walked through.
378
00:23:27,626 --> 00:23:31,246
If you're not feeling warm and fuzzy, to
where you're kind of like, it's still,
379
00:23:31,246 --> 00:23:35,956
I don't quite get it, I would seriously
suggest running through those nuggets again.
380
00:23:36,306 --> 00:23:39,336
Maybe just bounce it off somebody.
381
00:23:39,376 --> 00:23:40,876
Have somebody watch it with you.
382
00:23:41,086 --> 00:23:46,006
I will find that sometimes just talking
through my questions with somebody,
383
00:23:46,006 --> 00:23:50,256
that just when you get to a point, you
know, even if the person has no idea.
384
00:23:50,256 --> 00:23:54,066
If you're married this is the best thing for
your spouse to do, if they could help you out.
385
00:23:54,066 --> 00:23:57,976
Just have them sitting next to you
and be like, ok, let me stop it,
386
00:23:58,116 --> 00:24:01,486
when Jeremy said that, what did you understand?
387
00:24:01,486 --> 00:24:02,436
Did you get that?
388
00:24:02,436 --> 00:24:05,836
Because I will tell you, sometimes
even somebody that has no clue
389
00:24:05,836 --> 00:24:09,346
about networking will be your biggest
ally, to just talk it out loud with them.
390
00:24:09,596 --> 00:24:13,566
I will tell you, some of the most whacked
out network situations I've been in,
391
00:24:13,746 --> 00:24:19,536
I'm sitting here, you know, as, when I talk to
your right now, is how I am most of the time,
392
00:24:19,536 --> 00:24:23,646
you know, I'm just always, you know, I'm
thinking out loud, I'm pacing around rooms,
393
00:24:23,646 --> 00:24:27,936
I'm going, OK, OK so if I got
this, and I'm like, I don't get it.
394
00:24:27,936 --> 00:24:32,006
Why is this not, it should be working and you
know, God sends her in I believe, you know,
395
00:24:32,006 --> 00:24:36,776
my wife always walks in the room at just the
right time, and she's like, what's going on
396
00:24:36,776 --> 00:24:39,826
and I'm like, ah, it's just in
networking, don't worry about it.
397
00:24:39,826 --> 00:24:40,596
And she's like, no, tell me.
398
00:24:40,596 --> 00:24:44,486
And I'm like, ah, cause I know she
doesn't know what I'm talking about.
399
00:24:44,666 --> 00:24:48,096
So I'm like, OK, I've got a computer over
here, it's not talking to the server,
400
00:24:48,096 --> 00:24:51,916
I don't know why, and she's
like, uh huh, uh huh,
401
00:24:52,136 --> 00:24:55,866
and she might just be like,
so, can he surf the internet?
402
00:24:55,866 --> 00:25:00,386
And I'm like, well yeah, I
don't, that's, ok, hey go away.
403
00:25:00,386 --> 00:25:03,046
You know, I've got it, hang on, wait a second.
404
00:25:03,046 --> 00:25:06,546
So, a lot of times, she'll just
talking it through with somebody
405
00:25:06,546 --> 00:25:10,926
who may not even know a thing about
networking can sometimes help you out,
406
00:25:10,926 --> 00:25:14,466
so I would really encourage you to do that,
and then chalk through these four problems.
407
00:25:15,316 --> 00:25:18,226
So, two styles of subnetting you now have down.
408
00:25:18,226 --> 00:25:21,496
We've got subnetting based on the number
of networks, and then subnetting based
409
00:25:21,496 --> 00:25:23,646
on the number of hosts per network.
410
00:25:23,856 --> 00:25:24,706
Two more to come.
411
00:25:24,816 --> 00:25:28,966
That would be reverse engineering a
subnet problem, and then the ultimate,
412
00:25:28,966 --> 00:25:32,156
the pinnacle variable net subnet masking.
413
00:25:32,606 --> 00:25:34,976
I hope this has been informative for you
and I would like to thank you for viewing.
39085
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