Original subtitles

>> In the Arizona, just about every house has a pool, because it's so hot here all the time.

So, one of the key things you have to do is teach your kids to swim.

And I've found that, it's-- you reach, you know, different milestones in swimming,

but the toughest one is to go from the floaty thing down to nothing

to where they're just in the pool.

So, you know, your child will be standing on the edge and you're like "Come on honey, jump in,"

and, "No, I'm scared", and you're like, "No, it'll be fine, I'm right here, just jump in."

No I'm scared!"

You just got to reach the point where you get out of the pool,

pick up the child and jog him in.

You know, hey, wait, before you call CPS, you go in with them, right?

And you help them and they just got to tread water a little while and then they get in.

And then they'll like, "Oh, okay, this is kind of fun," and you'll help him around the pool

and all that kind of-- so, subnetting is the same way.

I have found that through, through many years of teaching, rather than start off with, "Okay,

well here's the con-- ," I mean, you just got to jump in.

You got to say, "Okay, here's the situation that requires subnetting, let's do it."

So in this opening IP subnetting nugget, I'm going to show you how

to subnet based on network requirements.

So here's the situation.

Here is something that would require custom subnetting.

This organization has purchased the Class C address 216.21.5.0.

Now, [inaudible] stop right there.

What do you mean purchase?

Why do I need to buy IP addresses?

Well, keep in mind than when we're working with IP addresses, there are private IP addresses

and there are public IP addresses.

The private one, you don't have to pay for, they are available to you, you can create them,

make them up whatever you want inside of your own network,

I believe we've talked about them already.

They are anything that starts with a number 10, they're anything with 172.16 through 31.255.255

if you will slash 16, or they are 192.168 dot anything slash 16.

So essentially if the first two octets are this, this, or the first octet is that,

it is a private address as in, they're yours.

You can create them, make them up, design your own internal networks all day,

but those IP addresses don't work on the internet,

they are blocked by every single service provider that are out there.

So, public addresses are anything that is a valid address outside of those ranges.

For example, this one.

So, this organization has purchased a block of public addresses that they want

to use inside of the organization.

They want all of the devices inside of their organization to be directly on the internet

without the use of NAT or any technology like that.

Now, is that normal?

I've seen it before, but it's not a normal thing,

but it works really well for a subnetting scenario.

So that's the situation that we've found our self in.

So the organization has purchased a Class C address that is this block.

So that means they can't go outside of that.

Now, when you purchase a Class C address, 216.21.5.0 with a Class C subnet mask,

255.255.255.0, how many networks do you get?

One, right, 216.21.5.

How many hosts do you get?

Well, 256 IP addresses total here, 254

that are usable 'cause you can't use 0 and you can't use 255.

So everything in that squishy [inaudible] center is usable on the host side.

But, here's the problem, let's look at this situation 'cause it says,

the organization has purchased this and we'd like to use it to address this network.

So we'll look at this.

Now, let me ask you the question, how many networks do you see in this picture?

Pause the nugget, think about it.

I see five, 1, 2, 3, 4, 5.

Essentially, every interface of a router represents the end

of a network and the beginning of a new.

So, if I connect another interface here to another group of computers, that would be six,

you know, there would be another network that would be represented there in that picture.

So, every interface of a router divides up a network and think about it,

that's what a router's life blood is.

It's to divide networks to stop broadcast like a broadcast that happens here

on this network stays on this network because it's--

that's all, you know, internal right there.

The router will not let that pass, you shall not pass.

So, we look at this and we go, "Okay, well this is-- this poses a problem."

We have our organization which has five networks, right?

But, we've purchased a Class C address

that only gives us one network, 216.21.5, inter-subnetting.

Subnetting or the full word, subnetworking,

is taking your one network and dividing it up into many.

Now, if I were to break it down even further, I would say,

it's sacrificing how many hosts you can have per network to get more networks.

So, essentially, we move this bar over a little bit more so that, you know, maybe half of that 0

if you will represents the network side and half of it represents the host.

Now, looking at it in a decimal sense, it's crazy,

you can't just draw a line through a 0 like that.

But when you break it out in binary and you go, "Oh, well, there's actually 8 bits,"

and actually, they're all 0s and that-- that's really 8.

There's 8 bits that represent that 0.

We could move the line over and maybe, you know, you could put a line in there,

somewhere that divide, you know, these 3 bits go

to the network side, these 3 bits go to the host.

That's what subnetting here is.

So here's the process, three steps every single time.

One, determine the number of networks that you need and convert it to binary.

Two, reserve the bits in the subnet mask and find your increment.

And three, use the increment to find your network ranges.

Now, at this point, those three steps don't mean anything 'cause we haven't gone through them,

so let's start treading some water.

This was the network that we were given, 216.21.5.0, that's what we purchased

from our internet service provider that we're going to subnet for our whole organization.

So step one is to determine the number of networks and convert it to binary.

Well, that's an easy step.

We determined on the last slide that there are going be five total networks.

Remember all every single one of those router interfaces represented a network

that they were connected to.

So, five networks and we need to convert it to binary number into our [inaudible] skills

from the last nugget, 128, 64, 32, 16, 8, 4, 2, 1 is our values that we're going to use

for subnetting are binary value, so no, no, no, no, no, yes, no, yes.

So five really represents 00000101 in the binary realm, that's it, that's the whole first step.

So, second step; reserve bits in the subnet mask and find your increment.

Well, what does that mean?

Well, the way that we do this is to take that subnet mask and look

at it the way our network devices look at it in binary.

So, now, you're going to want to shortcut this at the beginning, don't do it at the beginning.

I'll show you some shortcuts later, but while you're first starting in this,

you want to write that subnet mask in all binary.

It's not as hard as it sounds, right, 255.255.255.0.

What is that is a binary number.

What is 255?

All 8s or with all 8s [laughs], I'm totally wrong.

No, all 1s, it's eight 1s, one, two, three, four, five, six, seven, eight dot one two,

three, four, five, six, seven, eight dot one two, three, four, five, six, seven, eight dot.

So, I'm just converting that whole thing to binary and then what's 0 in all binary?

Real easy, right?

0000000, so that is what it looks like in all binary, okay.

So what does it mean to reserve bits in the subnet mask?

Okay, well, we have to look at this.

We say, determine the number of networks.

Now, I'm looking right here, okay five networks.

How, now, let me ask you a question.

This is a little tricky the first time you hear it.

How many bits did it take to get the number 5?

Three, 3 bits, that's really common.

You probably-- some of you probably did this, to look at this and say, "Oh,

well 2 bits 'cause I only see two 1s.

Well, you're thinking about it little of.

If you're thinking 2 bits, that's what it would mean, just those 2 bits.

What's the biggest number you could get with 2 bits?

Three, right, 1 plus 2 would be 3.

So we'll look at this and we go, "Okay, well, it's actually 3 bits.

I can't get the number 5 with any less than 3 bits, right?

So now, I need you to take another mental leap with me.

Previously, in all-- everything that we've talking about,

we've said 255 represents the network, 0 represents the host, right,

when we're lining up the subnet mask to the IP address,

that's how we find our network and host.

So, so I need you to take a mental jump with me.

Is it okay to make the statement, 1s represents the network and 0s represent the host?

So, is that an okay statement?

Yes, okay, okay good.

So we've got, 1s represent the network.

Okay, let's start putting some of these pieces together so I can't get the number 5,

I can't and let me put a little more to this.

It's like I'm unpacking this as we go.

So I can't get the number 5 with any less than 3 bits and I've just made the statement that,

that network bits really are 1s, so what does it mean when I say reserve bits in the subnet mask?

Here's what it means.

It means, I pick up right where the 1s leave off and I say, I need one, two,

three network bits, the rest of this can stay host.

I can't get five networks with any less than 3 bits,

so I'm going to add 3 more network bits onto there.

Now, whoa, stop the train, big statement right there.

Wait a second, wait a second, wait a second Jeremy.

I thought this was 101, why did you put 1, 1, 1 there?

Well, it doesn't really matter at all what the binary number is up here, at all.

What we're after is how many bits does it take to get that binary number?

If I had the number 20, I would look up here and I go, "Okay, well 20 is 00010100.

I don't really care if that is 101.

I just know that it takes 5 bits to get the number 20.

That's what I'm after.

I'm not really after the binary number at all, I'm just after how many bits.

So, when I come down here, I can say, "Okay, well, as I'm looking at my subnet mask,

I need five networks so I need to extend to that subnet mask

by 3-network bits to make that possible."

Okay, so believe it or not, at this point,

we already know what are subnet mask is going to be for this entire network.

How? Well, we can take this and convert it back to a decimal number, pretty straightforward,

255.255.255 because, these first three haven't change and frankly,

they can't change because that's what we're given.

We can only subnet the host bits 'cause that's our playground.

The 0s are where we can kind of make modifications.

This is what the service provider gave us.

That's what we bought so we can't change that.

So, what is this last one?

Well, that's where we have to use our binary to decimal skills.

I have to take this and convert it back to a decimal number.

So let's line it up, one, two, three, one, two, three, four, five.

So I really have to take 128 plus 64 plus 32, carry the 1 minus 2, 224 [laughs], yeah,

trust me, you'll start getting used to some of the common values.

They're going to say, it's the beauty of something and there's only eight numbers

that you're really going to run into.

So, our new subnet mask becomes 255.255.255.224.

Every router will have that.

Every computer will have that subnet mask in that network

that we just saw on the slide, that picture.

Everything will use that subnet mask and you can be like, "Yeah, doing the dance,

I got this subnet mask we're going to use for the whole network."

That's great, but it doesn't mean a thing to us yet.

It's just a number.

It's like, "Well, there it is, that's the right answer, choose C, you know, if you will,

but I don't know what that means yet."

Well that's the second half of this.

We reserve the bits in the subnet mask and find your increment.

What is the increment?

So we did the reservations.

So, the increment is actually the lowest network bit converted back to a decimal number.

So, let's think about it.

This 128, 64, 32.

The lowest network bit is essentially where the 1s end and the 0s begin.

The lowest network bit converted back to a decimal number represents our increment.

Okay. So, [laughs] still another one of those right answer things like,

"I got the subnet mask, I got the increment, I have no idea what it means yet."

Well the last step is to use that increment to find your network ranges.

Okay, this is where it all gets-- put together, 32 is our increment, this is what we were given

and we can start using that increment to find out how many IP addresses I get per network?

The way I do that is simple math, 216.21.5.0 is where I start.

And then I just start adding that increment in whatever octet, whatever position.

Let's look at it, it's in the fourth octet so I go, okay, next one is 216.21.5.1.32.

0 plus 32 is 32.

216.21.5.64.96.128, I'm just adding 32 dot, dot, dot, you know,

I just keep going down all the way, you know, filling those in and you can keep

that going down all the way as well.

What is that?

That is the starting position for each network.

216.21.5.0 is where network one begins and it goes through, you know, now,

we can go back once we just go down, we can go back and fill in the last IP address.

216.21.5 dot-- what's 1 less than 32?

I know some of you are like, "Is it really that simple?"

Yeah and it's not tricky, 31 right?

216.21.5.63 that's the last IP address before 6, so I'm filling in the last one just by looking

at where the next one starts and I go, "Okay, minus 1 and that must be that."

That fills in.

So, this goes to 216.21.5.95 and dot, dot, dot, dot, dot, dot, dot, you know,

this-- we'll just keep subtracting 1.

But now, it's become real.

Let me show you.

I come back here to my network situation and I realized I needed five networks.

So now, I can start assigning them.

This is actually going to be 216, no, network one 216.21.5.0.

through 31 with the 255.255.255.224 subnet mask, I won't write that every time,

but here's the subnet mask, here's the range.

So I will assign the devices in that network IP addresses in this range, 0 through 31.

So, you know, I would probably assign the router, the first one.

So the router would get 216.21.5.1 and then, you know, maybe a DHCP scope for the rest of them,

you know, maybe this computer is .2 and the next computer is .3 and all that kind of stuff.

That's-- they're actually go, "As long as I don't exceed 31."

Now keep in mind, whoa, whoa, whoa wait a second [inaudible] stop the train.

Remember, when we're doing IP networking, we can never use the first address or the last address.

Why? The first one represents the network and the last one represents the broadcast.

So, I can't actually assign something 216.21.5.0 because that identifies the whole network.

It's an identifier, it's not valid.

Same thing, I can't assign someone 216.21.5.31 because that's a broadcast.

If I wanted to send a message to everybody on that network, I would send it to that IP address

to .31 and everybody would get it.

That's a-- it's a broadcast address.

So we can't assign it.

So usable, we actually get 1 through 30 for that range.

So that's network one, you know, so that's number one right there.

Number two, is this guy, 216.21.5.32 through 63.

So, you'd come back here and say, "Okay, you are 216.21.5.32 through, what did I say 63,

63 but knowing realizing I can't give 32 or 63 to an actual device,

so 'cause that's the network, that's the broadcast.

So usable actually get 33 through 62 so maybe the router gets 216.21.5.33.

That's everybody's default gateway.

That's how they get off of their network is going to that 33 address.

And then this guy maybe is .34 and his friend is .35, you know, and all the other devices

that are on that network, get IP addresses that are in there as long

as I don't assign something to that.

So, what I've done, take a moment [inaudible].

Let's look at the concept.

I've taken the one network and broken it down to where I can address all

of the networks in this situation.

Now, let's fill in some questions.

Now, some of you mathematicians out there are looking and going, "Wait a second,

this is going to give me more than five."

I can see that, it's one, two, three, four, five and then I mean, this goes higher, right?.

It does, it's going to give you more than five because of how the binary works out.

Let's-- that's just, you know, if you look at it, you only have eight numbers

that it could be, so it's going be something in that range.

So you're-- the way to think of it is this scheme will give you

at least the five networks that you asked for, okay?

So, next question then becomes well, "How do I know, how many networks it'll give me?

Or, for that matter, "How do I know how many hosts I can actually have on the network?"

Well, there's a simple formula.

I say simple if you have a calculator, but simple to where you can type in 2 to the power

of how ever many bits you would like to put in there and find that question out.

So, let's do it this way.

Let's say, you're asking the question, "Well, how many networks does this give me?"

Well, the way you can find it out is to look at how many subnet bits you ended up adding.

So, 2 to the power of 3 in this case because I added three subnet bits.

So 2 to the power of 3 will tell you how many networks you get.

Now, 2 to the power of 3, it's a little simple 'cause you go "Okay, 2 times 2 is 4

and then 2 times, you know, essentially 2 times 2 times 2 is 8, you know.

If you're doing it in your head, it's like, "Okay, I can do that kind of math,"

but when you get into the larger numbers, it gets really tough,

so what if you don't have a calculator.

So, that's why I showed in the last nugget, these are all the powers of 2.

So 2 to the power of 0 is 1, to the power of 1 is 2,

to the power of 2 is 4, to the power of 3 is 8.

As long as you remember that it counts from 0, you should be fine, just go, "Okay,

well the 2 to the power of 3 is right here, so that's 8."

So you can do that and so that way, when you get to this larger number, you don't have to sit

with a piece of paper going 2 times 2 times 2, you can just look right here and go, "Okay,

2 to the power of 7 is actually 128."

See what I mean.

So 2 to the power of 3 tells you with this scheme, if I work this all the way down,

I will have a total of eight networks or eight subnetworks,

subnets that I created with this scheme.

Or, if I want to say, "Well, how many host do I get per network?"

Well, same formula, 2 to the power of, in this case, we're looking at host bits that's one,

two, three, four, five, five, there's five 0s left over equals,

you know, looking up here, is 32.

right?

But you have to remember, whenever you're doing the number of host, to always subtract 2.

What do you think that is?

You remember, right?

Can't use the first one, can't use the last one so those don't count.

So, we'll say usable host end up being 30 hosts per network, right?

You have just done your first subnetting question.

Now, [laughs] this is, you know, you grab the child and you throw him in the water, right,

they're going, [inaudible], you know, water splashing everywhere.

That's the kind of feeling that I have right now as you're going, "Whoa," you know.

It's kind of like I caught a little piece, I'm treading in a little water

and little bits here and there, but oh, man!

So let's do another one.

For this one, I'm going to skip the picture 'cause it just gets too big to draw.

But in this scenario, we've got a Class C network, 195.5.20.0

and we want to break that into 50 networks.

Okay, now, and let's get some bearing here.

That means that we've got one network, 195.5.20.0 with a Class C subnet mask,

255.255.255.0 and we want to take this one network,

'cause this typically gives us one network which is 195.520,

and break it into 50 different subnetworks.

[laughs] It's a question.

Is that even possible?

Can we do that?

Well, let's try it.

So first of, step number one, is to determine the number of networks and convert to binary.

So we need 50 subnets, all right.

Get a our old standby binary chart up here, 128, 64, 32, 16, 8, 4, 2, 1.

So 50 as a binary number, so I'm going to go 0, 0, 1, try that, oh, let me finish this

and then I'll give you my shortcut, 50 minus 32?

That will be 5, 4, 8, 1, 18 left, all right?

1, that would be 16, they'll be 2 left, so 0, 0, 2, 0.

[laughs] [inaudible], 0, 0, 1, on the 2 is 0, and there's a binary number.

So, 00110010, okay.

Step one, check.

We got it.

Now, step two, reserve bits in the subnet mask and find your increment.

Again, don't skip it at this point.

It's going to take a little bit of time but we're going to write the Class C subnet mask

in there and all binary, one, two, three, four, five, six, seven, eight, one, two, three, four,

five, six, seven, eight, one, two, three, four, five, six, seven, eight, okay.

So, here's what I want to show you a little shortcut.

So the statement is reserve bits in the subnet mask and find your increment.

So, we have to ask the question, how many bits did it take to get the number 50?

And I would submit to you, 6 bits

because I can't get the number 50 with any less than 6 bits, okay.

Into your shortcut number one here, one of the things we're always trying

to do is do things a little bit faster especially when we're talking

about certification exams and time is on the line and all that, you want to try

and do things as fast as possible.

When you're finding the binary number right here where it says, determine the number of networks

and convert to binary [inaudible], when you're finding that binary number,

as soon as you put the first one on the drawing board,

do you know how many bits it's going to take to get that number?

Yeah, right?

So, as soon as I know my first one goes at the 32, I don't have to spend time figuring

out the rest of this because I know, no matter what the rest of this is,

I don't really care what the rest of this is.

I just care that it takes 6 bits to get 50 networks, right?

So, that can save you a little bit of time there.

Okay. So now, we're going to do step two which is reserve the bits in the subnet mask.

Now, are we after-- here's my question-- next question for you, are we after 50 networks

or are we after 50 hosts on our networks?

Well, the answer is 50 networks.

You're like, you know, "We'll, Jeremy, that's what the question says, 50 networks, right?"

Well, yes, and I'm going to keep asking you this question and the reason why is because later

on in the next nugget, we're going to change that question a little bit

to the host per network, but for now, 50 networks.

So, I go, "Okay, I need-- that means then, I need 6 network bits, right?"

And we know that 1s are network bits, so I'm going to go one, two, three, four, five, six,

it does-- again, it doesn't matter what these were at, it doesn't matter,

I need 6 network bits 'cause I can't get 50 networks,

I can't get 50 subnets with any less than 6 bits.

Okay, 0, 0 is left over, not much for the host, right?

So, that gives us what our new subnet mask is.

In decimal form, we know the subnet mask

for the network will be 255.255.255., now what is this in decimal?

Well, two approaches you could take.

You could add 128, 64, 32, 16, 8, 4 all together, right?

And you could that number or if these are all 1, we know that they're 255, right?

So, in this case, it will be a lot easier just to figure out what we don't have.

We don't have a 2 and we don't have a 1, right?

So, we could either add all these numbers up and get the answer

or we could take 255 minus 3 which gives us 252.

Forgive me, I'm starting to throw a little shortcuts in here as we go,

just go a little faster, 252, but if the shortcuts don't work for you,

you know, add them up, definitely.

It's much better to take a little more time adding

and get the right answer than go, "How was that again?"

So, 252 is our subnet mask.

Now, let me add yet another piece.

I add these little pieces as we go through this to enhance what you know.

Now, we've been talking all along, you know, we've been saying--

I think I'd showed you in an earlier nuggets

like a slash 24 really equals 255.255.255.0, right?

That's kind of a shorthand, that's called CIDR notation and all that and I said

like slash 8 equals 255.0.0.0, all those kinds of things.

Now, we can actually see why?

This CIDR notation is really just the number of 1s in the subnet mask.

So, when I look at a Class C subnet mask, I can say, "Well, that's 255.255.255.0" or I can say,

"Well, that's eight 1s, eight 1s, eight 1s,

so that 24 1s thus slash 24 is a shortcut way of writing that.

You see why it's kind of cool?

Once you know the binary, you're like, "Oh, that's where they get that from."

So, you know, a Class A address only has 8 bits in that so it becomes a slash 8.

So, the reason I say that is I want to start writing this, you know, this is--

we started with a slash 24 here but I want to start writing this in both decimal

and CIDR notation because you're going to see examples of both

in the real world and on the exam.

This, 255.255.255.252, is actually the original 24 bits plus 6 more that I added there, right?

That'll be a slash 30.

That would be representative of that subnet mask.

So, again, we're just talking about ways of writing the subnet mask.

I can write it this way or I can write it that way.

They both mean the same thing.

So, okay, let's catch back up where we were.

We determined we needed 50 networks, that's what the question gave us.

We determined it was 6 bits, so we reserved our 6 bits,

so now we know what our subnet mask is going to be for this whole network.

So now, we need to find our increment.

So, I'm going to come in here and let me say, "The lowest network bit,

the last network bit converted back to a decimal number is a 4, [inaudible]."

That is my increment.

So I can come in here and say, "I'm going to use that increment to find my network ranges,

195.5.20.0 and just start adding 4 to the last octet 'cause that's where the increment is."

So, 195.5.20.4, .20, just go on faster, .20.12, .20-- you see where this is going, .16 dot, dot,

dot, dot, dot, dot, down, down and down we go.

So that's the start of every single network that I would need for this organization.

So what's the end?

Well, just subtract 1, 3, subtract 1, 7, subtract 1, 11.

So this-- these are actually go-- now, I'm writing the shorthand.

It's actually 195.5.20.0 through 195.5.20.3 through, you know, you see what I mean?

So I'm just writing them shorthand.

Now, keep in mind, we know that we cannot use the last IP address

or the first IP address, so what is our usable?

1 through 2.

What is our usable?

5 through 6.

We actually have two, count them, one, two usable hosts for our network.

And if you think about it, if we're taking a Class C and breaking in into

at least 50 subnets, well, good grief, we have to give somewhere.

Now, you might be saying and scratching your head going, "Okay, this is just getting absurd.

Where would we use a subnet mask that only has two hosts per network?"

Well believe it or not.

You just found the second most subnet-- most coomon subnet mask in the world.

The most common subnet mask is a slash 24.

The second most common subnet mask is a slash 30 because it's used all

over the place when you have WAN links.

Oh man, what a perfect fit.

So, if you have router one connected to a network up here, you know,

that you got your computer's humming along up there.

Router two is connected to a network down here.

And then you've got a WAN link in the middle managed by AT&T

or whatever service provider you're using to connect, that we'll say, the Arizona office

to the Texas office, to connect these two sites.

Well, this is a network and I don't want to waste IP addresses on that network

because I know I'll only have how many?

Two devices on that network.

One here on this side, that's our router, and one here.

This is such a custom fit for this kind of environment because I can say, "Okay, well,

this will be the 192.5.20.0 network slash 37 netmask.

So, you will actually be .1 and you will be .2, the two usable IP addresses.

And then all of a sudden, Texas has a need to have a link

to the new Michigan office, router three.

All right here, we've got another network, you know.

We have a network down here.

Now, of course, we wouldn't use this kind of subnet mask on the network down here

because you would only be able to have two devices in that network.

That will be-- that would be absurd, you're right.

But for the WAN link going between Texas and Michigan, sure,

let's make that guy 192.5.20.4/30.

Again remember, this represents the network.

So, when I'm writing documentation, I'm diagramming, I'm saying, "Oh, yeah,

it's the .4 network slash 30, so he'll be .5 IP address, he'll be .6.

Okay, so how's it feeling?

Are you getting-- get a little water treading going on over your heads above why you're like,

"Okay, I saw what you did, some of the pieces are starting to make sense,

make sense, let's do another one."

You know, that-- hopefully, that's the feeling you're getting.

So, what I'm going to do is change it to where we're moving beyond Class C only examples.

So, we're going to start with a Class B address.

Now, you remember?

The Class B addresses by default are slash 16 or 255, 255, 0, 0.

So only the first two octets represent the network now.

So, let's start there and see where that leads us.

So, number one, okay.

So, let's look at our situation first.

We have a Class B network, 150.5.0.0.

and we want to break that into 100, kind of 100 individual subnets or 100 individual networks

to disperse around our organization, okay.

So, with that in place, let's start of.

Determine the number of networks and convert to binary.

Well, it was given to us.

We needed 100 networks.

So let's bring up our binary charts 64, 32, 16, 8, 4, 2, 1.

All right, so 100, let's use our shortcut [inaudible].

Our first one goes right there, right?

So, from the last example we did, we know we can stop because we know that 100 takes 7 bits.

Now, again, if that throws you off, then, you know, continue on.

I think-- is that 164 plus 32, that'll be 96, right.

Yeah, that should be 100.

So you could figure out the whole binary value but still, it would still be 7 bits

that we get by the time it's said and done.

So, we're after the number of bits because we need them in step two.

Reserve bits in the subnet mask and find your increment.

Now, our subnet mask, and this is why it's so-- you might be like, "Well,

I'm kind of tired writing 1s and 0s, it's so super critical that you do especially

when you get to the non-class C examples 'cause you want to see where you're at.

So, one, two, three, four, five, six, seven, eight, dot, one, two, three, four, five, six,

seven, eight, dot, one, two, three, four, five, six, seven, eight.

One, two, three, four, five, six, seven, eight.

Good. So that's our subnet mask in all binary for Class B subnet mask.

That's where we started with this.

So, we have 150.5 that we're working with.

So, I'm looking-- I can't get 100 networks with any less than 7 bits.

And I remember that I'm after networks, I'm not after a host per network.

So those are the 1s, I need more 1s, how many of them, seven of them.

Now, I'm going to start where the 1s leave off.

One, two-- hang on, I can't do that.

I need another color.

One, two, three, four, five, six, seven, zero.

One, two, three, four, five, six, seven, eight, I'm super visual.

Everything I do is-- I have to draw it, I have to write it.

It's funny.

It's-- I'm so-- I'm such a visual learner.

It's to the point of handicapped to where when somebody talks to me,

if their sentences go beyond like three sentences, if it's a network situation,

I'm like, "Let's go to a white board."

I have a 2,000 square foot office that I work in when I'm not working out of my home.

I literally have nine white boards put up around the office.

Like every room have at least two white boards on the wall.

You know, like some people put up art, I put up white boards 'cause I have to do that.

So forgive me when I'm like I need color, I need something new.

So, I've reserved my 7 bits.

Now, be careful, it's so easy when you're doing this to think in a Class C. So,

you might have your, you know, the bunch of 1s and then you got one, two, three, four, five,

six, you know, dot, one, two, three, four, five.

So, right here, sometimes people mistakenly start in the last octet, you know,

because they're so used to Class C examples

like they would start putting 1s right there instead of where the 1s leave off.

Always pick up for the 1s leave off.

You don't want to have 1s here and nothing there, that-- it just doesn't work that way.

So, at this point, we know what our subnet mask is going to be.

It's now 255.255 dot-- I'm looking at that third octet now.

Now, again, you can add all these numbers up, 128, 64, 32 or you can just remember

that it's 255 and I don't have a one.

So that would be 254.0 is our subnet mask.

CIDR notation.

Originally, we had a slash 16 and now we graduated ourselves

to a slash 23 'cause we added 7 bits on to our 16 right here.

So, that's our new subnet mask insider, that's our new subnet mask in decimal notation.

What's our increment?

Another place where a mistake could easily be caused by kind of logically thinking--

you're thinking, "Okay, my increments are one, two, three, four,

you know, you start-- not one, two, three.

One, two, four, eight, 16.

You start counting and you're like okay, 120, so this must be-- you see what I'm saying?

256 but no.

That's not the way to think about it.

Don't count from far right.

Every octet is a new set of increments, right?

So you've got one, two, four, eight, 16, 32, 64, 128 here, then we start over.

One, two, two, four, eight, and so on and so forth.

So, our increment is a 2, right?

The lowest network bit converted back to a decimal number.

Good. Okay.

So now-- so it's working out, I mean, I'm just kind of showing you the little pieces here

and there where you could trip up but it's the same exact thing as it was previously.

So, now let's write our network ranges.

So we've got 150.5.0.0 because that's what we were given.

Now, be careful.

I need to add my increment, add my two in the octet where it's at.

Now, I'm not working in this octet, I'm working in this octet, the third octet.

So, that's where my 2 gets added.

150.5.2.0, 150.5.4.0.

You see what I'm saying?

150.5.6.0 and down and down and down we go nonetheless.

Good, good?

Okay. Okay, last place where you could easily trip up in something like this is to look at it

and go, okay, this is going to go through, you know, so my range,

the usable addresses are going to go through 150.5, okay subtract 1, right?

So, .1.0. That's actually not right.

"Well, why not, Jeremy?

What's wrong with that?"

Well, my question is, if this one ends at 150.5.1.0, and this one starts at 150.5.2.0,

so this is right, this is the end, this is the begin of the next range, all right?

Are you following?

Where does 150.5.1.50 fit?

Well, you're like, "Well, it's in the first."

No, I'm sorry.

Our range ended at 0 there.

That 50 is greater then 0 and you go "Well, it's over here."

No, that started at 2.

So, where does that guy fit?

Where's 150.1 dot-- well, anything, 150.5.1.200 fit, where does fit?

It doesn't.

We left them out in the cold.

So, we have to go back, we have to revise our numbers.

Let me just wipe these guys off.

Revise our numbers here to say, no, no, no [inaudible].

Let's get you out.

This actually ends at 150.5.1.255.

That's the actual-- last that I'd like-- think of it as some bizarre lot-- math problem.

Remember when you're first learning math and they go, "Okay, 19,

what happens if I add one to that?"

And I mean, you got to reduce yourself back to an elementary mindset, right?

You kind of like, "Oh, well, I can't have 10 there because I can only have one digit

so I have to just kind of 0 it out and carry the 1 if you will, right?

So, we're in 20.

So, think of it in like bizarre math world, right?

You know that 255 is like your 9 because you can't have any more than that with 8 bits.

So, if we add 1 to that, what happens?

Well, we can have 256.

It doesn't-- that value doesn't exist with 8 bits.

So, it kind of zeros out and carries the 1 so you're down to 2 here, right?

So, [laughs] if that works for you, oh great.

If not, then forget I ever said it.

So, that's going to follow that same trend the whole way down.

This goes through 150.5.3.255, sweet.

Through 150, you see how this is working?

5.5.255, cool, down and down and down we go.

Come on, you got to be looking right and go on, "Okay, okay I'm feeling it.

I'm seeing how theses pieces are starting to fit in the place, right?"

If not, I would say, stop here, rewind, go back through it a few more times because it--

like at this point, I would suggests it would be soaking in where you're like, "Okay, okay.

I'm starting to see how this-- I don't know why these weird things like this horse rides."

So this is like [laughs] I know, what I mean like, I'm starting to see the feel of it.

Okay. Now let me throw something else at you.

I'm like, [laughs] "Okay, you think you got it?"

Well, let me show you something.

So, somewhere in the middle of this range, right?

You're going to run into the IP address 150.5.0.255,

right, somewhere in the middle there.

You're also going to run into the IP address 150.5.1.0, that's right next to that guy right,

right, kind of in the middle of that range.

So, again, it's let put this back in the terms of network situation.

We've got computers connected to a router.

I mean, this company needed 100 networks.

So maybe it's something like this where they've got, you know, corporate headquarters

and I they've got all these kind of networks over there and computers and all that,

and that corporate headquarters goes to all

of these branch offices like-- let's, you know, identify.

Let's-- maybe it's like a wells Fargo Bank or a State Farm Insurance,

I'm just throwing companies out there that I would assume would follow this model

to where they have kind of corporate headquarters

and then all these little branch offices, street mall, you know,

ATM machines, I mean, it's funny.

When you, you know, how-- when you get a car like you're driving a new car

and you're looking around, you're like, "Hey, I see like so many of these cars on the road.

It's not that there's anymore, it's just now that you have that car, you see it everywhere.

It's the same thing, when you start getting at the network world, you'll be walking in a store

and you're like, "I wonder how they do the network for this?"

I want to-- like I walked in Walmart.

I don't see stuff on the shelf anymore, it's like the matrix.

I just see, you know, binary 1s.

You know, I'm like, "How does Walmart?"

I see a guy with hand scanner.

I'm like, "Oh, that's connected to a WIFI network, I wonder how they design,"

like that's the kind of thought you have.

So this is Walmart, right, and this is store 1, store 2, store 3, all that kind of stuff,

so all these different stores, so, you're like, "Jeremy, come back to us," I'm back, okay.

So, this network one gets assigned to store 1, right?

So, can I go to this computer at that store or that hand scanner or whatever device that is

and give it the IP address 150.5.0.255.

Can I assign this IP address to that computer?

[Inaudible], did you get it?

Yes, you can.

[laughs] No, and somebody like, "No, but it's--

but no, it's 255, you can't use 255, isn't that the broadcast?"

No, once we've gone beyond a Class C example, we've come into a world where there--

we're kind of moving between big ranges if you will

to where there's only one network and that's 150.5.0.0.

And there's only one broadcast on this network, 150.5.1.255,

everything in the middle is fair game.

So, yes, this is a valid address.

Yes, this is a valid address.

You can't, now it's going to feel really weird.

You're going to be like, "This ain't going to work out.

I can feel it now, it's not going to work."

It will work.

It will work as long as you give it this subnet mask

because that tells the computer exactly what the range is.

So, I mean same thing down here, you would run into, you know, in this range right here,

you'd run into 150.5.4.255, somewhere in there.

Does it work?

Can I assign that to a device?

Yes, you ca and it will work.

That's the power that we have with these ranges.

So, already, I know some of you are real world, some of you are really heavy focused

on the certification exam, if your certification focus already be thinking of the test question.

Based on this IP address and based on this subnet mask,

which of the following are valid addresses?

And I guarantee you those guys are going to show up in the list

and be, "Oh, no, those aren't valid."

Oh, yes they are depending on the subnet mask that you use, they definitely can be valid.

Okay, one last example, this one a Class A example.

We've got the 10 network, 10.0.0.0 and we need a thousand networks.

Now you remember class A subnet mask gets a slash 8 or 255.0.0.0 and we need to break

that into a whole big number of networks, is that even possible?

Well, let's find out.

First off, we need to determine the number of networks and convert it to binary.

So, I'm going to take a thousand subnets equals--

okay, wait a second, we've gone outside of our 128, 64 world or 8 bits 32, 16, 8, 4, 2,

1 'cause we know the biggest number that we can get with this is 255, so can we do it?

Yeah, we just need to stretch a little bit more.

So I'm going to go to the next decrement, 256.

If I multiply, you know, powers of 2 to the power of 8 is 256 or 128 times 2,

then we multiply that by 2 and that would be 512.

Okay, is that big enough?

Well, let's multiple that by 2 and we go, okay, 1,024.

Okay, we've exceeded a thousand network.

So I know my 1 can't go right here, that's not possible because I can't subtract 1,024

from 1,000, so my first one goes right there.

Now again, you can figure out the entire binary number for 1,000 but I would say,

especially in a number this big, it makes it a lot faster for you to say, okay, well,

how many bits did it take to get the number 1,000?

Well, we had our 8, 9, 10, a thousand is 10 bits.

All right, so reserve bits in the mask and find the increment, our original subnet mask

because it was class A is 255.0.0.0.

In binary, it looks like this two, three, four, five, six, seven, eight.

Two, three, four, five, six, seven, eight.

Now, remember all these 0s are ours.

It's our playground to work with.

I got 2 [inaudible] either.

Yeah, [inaudible], there we go.

So, we've got our subnet mask in all binary.

Now, we go back to the question, what do we need, 1,000 hosts per network or 1,000 networks?

Well, in this case 1,000 networks.

We know that to get the number 1,000, it's 10 bits and we know that network bits are 1s,

not 0s in the binary scheme of thing.

So, we pick up right where the 1s leave off and we say, one, two, three, four, five, six, seven,

eight, oh I didn't line them up exactly but that's eight, and lines up to the eight,

dot nine, ten 'cause we needed 10 bits to get the number 1,000.

I can't do this with any less then 10,

so we actually cross the dotted line if you will into that.

The rest of these can stay 0.

[ Pause ]

That's our new subnet mask.

So we've added 10 network bits, so our new subnet mask goes 255.255 dot--

let's see what this one, 128 plus 64 since we have kind of those two lit up in this octet.

So, that would be 192.0, so that's the decimal version or we're moving from a slash 8 up here

down to a slash-- that will be slash 8, slash 16, the first two, 17, 18 'cause we added two

in that last one, so we're going to a slash 18 subnet mask, good.

So, now the question what is our increment?

Well, our increment is right here.

Lowest network bit back in binary.

Again, nothing funky, every single octet restarts the increment,

so that's a 64, like that.

And now, we just start adding that increment to find our network ranges.

So, I'm going to start with Class A. Let's see where do I begin?

10.0.0.0 is what we we're given, 10.0.0.0, okay.

What octet is our increment in?

This one, the third one over, right?

So, I'm going 10.0.64.0.

Whoa, 10.0.128.0, I'm adding 64 in that third octet.

10.0.192.0 and down and down we go.

Now, I'm actually going to come back to my down and down and down statement in just a moment,

but let me fill in the end ranges first.

So, this one is going to go through 10.0 dot--

now remember from the last one, this little trick 63 dot what?

255. This one goes through 10.0.127.255.

We can't cut off that end range, so we're-- just like the last one, we're going through that

and we would continue this way all the way down.

This goes through 191.255.

Again, just the last two octets that I'm putting in.

Now, let me ask a question on this lesson.

I want to-- this is what I want to come back to.

What do you get if you add 64 to 192?

Let's do it.

192 plus 64 equals 6, 5, carry the 1, that'll be 2.

Whoa, buddy, hey wait a second.

We-- so you're saying if we keep going with this increment, we're going to get 10.0.256.0.

No, that's broken, we can't do that.

Well, if you hit that point, don't worry.

You haven't done anything wrong, that just tells you've reached the end of an octet.

So, hang on, before we do anything more, let's fill in--

what would the last IP address for this range be?

It will 10.0 dot-- what's subtract 1 from 256?

255.255. Just-- I should erase this

and write the whole thing just so it looks nice and consistent.

So, this goes to 10.0 dot-- what, 191.255, right?

So go on with this.

This goes 255.255 right there.

So, what that tells you is you reached the end.

Now, wait a second.

The end, what do you mean?

We're after a thousand networks and we only got four right?

How do we get a thousand networks when we're at the end right there?

Well, we're at the end of our first kind of major octet.

Our first-- we're at the end of the 0s.

So again, think of that bizarre math world.

If I said plus 1, you know, [inaudible] and then I say, "Okay,

what's the next IP address after that?"

Well, 256 would zero out, carry the 1.

So this would zero out, carry the 1 and we move over to 10.1.

And see what we're going here?

So, there really is no 10.0.256 dot-- oh, I can't do that.

There is no 10.0.256.0.

The next one will actually go to 10.1.0.0, that's our next IP address,

and then we start the whole thing all over again, 10.1.64, 10.1.128, you know,

just kind of keep going down with that counting.

And once you see the scheme of how this works and I'm squeezing

at the bottom, 10.1.128 is there.

You see the scheme, it just-- and now, you start looking, oh,

that's how we get a thousand networks.

Every single one of these octets all the way up to 255 gets four networks a piece,

that makes sense, you know, it's where-- now I can see where that fits in.

So, this is just kind of repeats itself.

That's why I wanted to do this example.

You might say, well, we've already seen kind of a Class B. Well,

I wanted to show you again breaking

that paradigm a little bit more to see all of that is possible.

Now, there're always two levels of learning.

There's one where you can watch somebody who's explaining it, like me, and go, "Okay, I get it.

I kind of see what you're doing.

I see what you're following and that-- like that's a major milestone."

Congratulations if you're at that point.

If you're not at that point, then, you know, rewind, go back through it again,

just keep watching until you're like, "Oh, that-- it's starting to click, it makes sense."

But there's a second level of learning that you absolutely need to reach with every concept

in the Cisco world, but especially this one, and that is the level of doing it yourself.

So right now, I want to transfer you to-- from level one to level two,

by giving you this homework assignment.

You can see all it is-- I put the class of network that is.

So, this is a Class C network, Class B network, Class A network.

So, I've got four examples for you to work through, and to check your work,

I'm going to include a supplemental file with this nugget.

You can actually download it.

I think it's-- I think that the supplements are all included in one big zip file,

but you can download it, so you're able to check the work.

And I'm going to write this file in such a way that it's kind of step by step.

It's broken down as if I was explain--

it's the best I can do in writing style to explain what I'm doing

as I go through each one of them.

So, right now-- before its seeps out of your mind, sit down with a piece of paper

and see if you can work through these.

Try not to look at the answer, because these are the four examples that I'm giving you,

try not to look in, go back through the lecture and see if you can kind

of piece together the steps and get through them all yourself, and then check your work.

Also, realize that there are literally thousands of free examples

of subnetting questions out there in the internet.

The world knows that this is a hard topic to get.

So, you will find-- if you just go on Google and type in subnetting examples,

you'll find slide after slide after slide that gives you practice problems

and so on that you're able to work through and check your work.

Well, that leads us to the end of subnetting style 1

which is creating subnets based on network requirements.

As we move in to the next nugget, we'll start expanding on different styles of subnetting,

different styles of examples, but for now, I hope this has been informative for you

and I'd like to thank you for viewing.