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Cisco CCNA certification proves your professional worth. It tells prospective employers that you can handle the day-to-day work of running a mid- to large-sized Cisco network....
Cisco CCNA certification proves your professional worth. It tells prospective employers that you can handle the day-to-day work of running a mid- to large-sized Cisco network.

The two-exam CCNA process covers lots of innovative features, which better reflect the skills and knowledge you'll need on the job. Passing both exams is your first step towards higher-level Cisco certification, and trainer Jeremy Cioara has mapped these CCNA training videos to the 640-816 test. This CCNA training is not to be missed.

Here's how one user described Jeremy's training: "By the way, Jeremy Cioara has to be by far one of the BEST Cisco trainers I have ever had the privilege to learn from overall. He not only keeps your attention but his energy is contagious and he provides the information at a level where you grasp it rather easily."

The last day to take the 640-816 exam is Sept. 30, 2013. After that date, the only ICND2 exam available will be 200-101. CBT Nuggets has a training course for the 200-101 exam here.

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1. Review: Rebuilding the Small Office Network, Part 1 (33 min)
2. Review: Rebuilding the Small Office Network, Part 2 (28 min)
3. Review: Rebuilding the Small Office Network, Part 3 (23 min)
4. Switch VLANs: Understanding VLANs (16 min)
5. Switch VLANs: Understanding Trunks and VTP (39 min)
6. Switch VLANs: Configuring VLANs and VTP, Part 1 (35 min)
7. Switch VLANs: Configuring VLANs and VTP, Part 2 (39 min)
8. Switch STP: Understanding the Spanning-Tree Protocol (28 min)
9. Switch STP: Configuring Basic STP (21 min)
10. Switch STP: Enhancements to STP (29 min)
11. General Switching: Troubleshooting and Security Best Practices (29 min)
12. Subnetting: Understanding VLSM (18 min)
13. Routing Protocols: Distance Vector vs. Link State (26 min)
14. Routing Protocols: OSPF Concepts (30 min)
15. Routing Protocols: OSPF Configuration and Troubleshooting (39 min)
16. Routing Protocols: EIGRP Concepts and Configuration (32 min)
17. Access-Lists: The Rules of the ACL (27 min)
18. Access-Lists: Configuring ACLs (34 min)
19. Access-Lists: Configuring ACLs, Part 2 (48 min)
20. NAT: Understanding the Three Styles of NAT (20 min)
21. NAT: Command-line NAT Configuration (35 min)
22. WAN Connections: Concepts of VPN Technology (33 min)
23. WAN Connections: Implementing PPP Authentication (34 min)
24. WAN Connections: Understanding Frame Relay (28 min)
25. WAN Connections: Configuring Frame Relay (30 min)
26. IPv6: Understanding Basic Concepts and Addressing (34 min)
27. IPv6: Configuring, Routing, and Interoperating (23 min)
28. Certification: Some Last Words for Test Takers (13 min)
29. Advanced TCP/IP: Working with Binary (25 min)
30. Advanced TCP/IP: IP Subnetting, Part 1 (55 min)
31. Advanced TCP/IP: IP Subnetting, Part 2 (22 min)
32. Advanced TCP/IP: IP Subnetting, Part 3 (19 min)

Review: Rebuilding the Small Office Network, Part 1

Review: Rebuilding the Small Office Network, Part 2

Review: Rebuilding the Small Office Network, Part 3

Switch VLANs: Understanding VLANs

Switch VLANs: Understanding Trunks and VTP

Switch VLANs: Configuring VLANs and VTP, Part 1

Switch VLANs: Configuring VLANs and VTP, Part 2

Switch STP: Understanding the Spanning-Tree Protocol

Switch STP: Configuring Basic STP

Switch STP: Enhancements to STP

General Switching: Troubleshooting and Security Best Practices

Subnetting: Understanding VLSM

Routing Protocols: Distance Vector vs. Link State

Routing Protocols: OSPF Concepts

Routing Protocols: OSPF Configuration and Troubleshooting

Routing Protocols: EIGRP Concepts and Configuration

Access-Lists: The Rules of the ACL

Access-Lists: Configuring ACLs

Access-Lists: Configuring ACLs, Part 2

NAT: Understanding the Three Styles of NAT

NAT: Command-line NAT Configuration

WAN Connections: Concepts of VPN Technology

WAN Connections: Implementing PPP Authentication

WAN Connections: Understanding Frame Relay

WAN Connections: Configuring Frame Relay

IPv6: Understanding Basic Concepts and Addressing

IPv6: Configuring, Routing, and Interoperating

Certification: Some Last Words for Test Takers

Advanced TCP/IP: Working with Binary

Advanced TCP/IP: IP Subnetting, Part 1

00:00:00

Ahhhhh. All right, are you ready for it? We have arrived at advanced TCP/IP: IP Subnetting, part one. If you haven't looked at the bottom of the window yet, this video will take a little extra time because I'm going to fully walk through multiple examples of subnetting based on network requirements. Four different ones to be exact and then leave

00:00:28

you with a bunch of practice to do on your own. Now, one of the things that I've found is the best way to teach subnetting is not just to start talking about the -- the advanced pieces of it right away and -- and say oh this is, you know, this is what subnetting does and binary addition and all that. It's more so to apply

00:00:47

it to the real world. So you can see that we have four separate scenarios, four different network requirements that we're going to walk through one by one as we determine how to break a network into multiple sub-networks one by one. Let's get going. Let's start off with network scenario number one. We have an

00:01:08

organization, this organization has purchased a Class C address 216.21.5.0, so they've purchased that from the powers that be, the Internet, and they now want to use it to address this network. And this is a picture of their network. Now here's the trouble and this is why we need

00:01:27

subnetting. They purchased a Class C network and let me just write it over here, 216.21.5.0. Now, when they bought that, it's a Class C network so the subnet mask is this. The question I have is how many networks do they get from that? Well, looking at it, it's just one. We draw our line boundary right

00:01:50

there and 216.21.5 represents the one network they get; that's their network. And this over here represents the host. It goes from 0 to 255 maximum where you can't use zero and you can't use 255. You get everything in between; you can't use the first and last address from -- from the network range. So we have 254 hosts on one network. Now look at their network diagram. How

00:02:14

many networks do they need? Well, let's number them, one, two, three; and a lot of people forget these -- four and five. Remember every interface of a router is a network. So we need a network address or a sub-network -- a network -- for every single one of these locations. Here's maybe an office with an ethernet switch

00:02:42

maybe that's in Arizona. We have an office across the WAN link to California. The WAN link to get there is considered a network and the office itself. Now we have a WAN link over from California to Florida, which we have an office right here and the WAN link itself to get there. So we have one network that we purchased

00:03:01

but we need to break it in to five. So we know our network requirements now. Now here are the three steps of subnetting. Before we start working through this, let me give you a little disclaimer. First off, I wrote our network requirements up here. This was our Class C subnet mask that we needed and we know that we needed five networks or sub-networks based on what we saw on the previous slide. Now the disclaimer that I have is that there

00:03:28

are more ways to subnet than there probably are grains of sand on the sea shore. I mean, literally I, even myself over the twelve years of teaching that I have been in, have taught this probably six or seven different ways. About five years ago, I came up with this little three step process that will work for just about any subnetting scenario you can throw at it. And you'll

00:03:49

be able to -- to figure out the answer. Now the first time we work through this together, it's going to look a little weird and you're going to go, ah, I don't know about that. But I'm telling you after about the third or fourth example of this, you're gonna start going, oh, I see how this is working. And between this and the following video I hope to

00:04:09

give you enough examples and practice that you can work on yourself, so that you'll be able to master the skill and master it quickly. So our first step in this subnetting scenario is to determine the number of networks and convert it to binary. We need to use this skill that we learned previously in the previous video, of binary conversion. So we know that we need

00:04:31

five networks, let me write up our binary chart. 128,64,32, 8, 4, 2, 1. So five is a binary number is no, no, no, no, no, yes; there's our first one -- four zero one. So we know that five is zero, zero, zero, zero, zero -- five zeros -- 101; that's our binary equivalent. That's all there is to step one.

00:04:57

The second step is the big one. Reserve the bits in the subnet mask and find your increment. Now I am going to show you something and I want to make sure that when you start working on this you don't skip this, this step or this part of the step. It may seem tedious at first, but you will greatly appreciate this after a little bit. We need to write our regional subnet mask

00:05:22

right here, in all binary. So 255.255.255.0 is Class C. Now what's 255 in binary? All ones; that's the biggest number we can have, right? So 8 ones dot -- this is the whole subnet mask; eight ones, one two three four five six seven, eight dot eight more ones; one, two, three, four, five, six, seven eight dot and now zero in binary is just all zeros. One

00:05:47

two, three, four, five, six, seven, eight. Now I need to have you make a mental leap with me; a transition. We've been looking at subnet masks, like this, up till this point and we've been looking at them in decimal format. Everywhere we see 255, we go oh, well, that represents the network. So we know 216 represents part of the network. 255, oh 21 is part of the network. So we've been relating 255 equals network and wherever we see the zero, that represents the hosts. But here's the leap I need you to make. We need to

00:06:23

start thinking in terms of binary, so can I say wherever I see ones as binary numbers that represents the network. And wherever I see zeros as binary numbers, that represents the host. Is that an okay leap to make? Good, so what -- the beauty of of video recordings as I can say, good; we're all on the same page and we are. So we have right here our -- our 24 ones that represent the network and our 8 zeros. Now what's our goal here? Our goal is to create more networks. Meaning, we only have

00:07:00

one network and I need to create more, five of them to be exact. Now how many bits does it take to get the number five? Three of them. Three bits, right? You can't get the number five with any less than three bits. Now, when I asked that question, I know you may have been thinking, well, two bits, right? Because there's only two ones there. But if you look at this, if you only have

00:07:25

two bits, what's the biggest number you can get? Three, right? If two plus one -- you can't -- you can't get the number five. So I'm not looking when I asked that question for how many ones do I have, I literally want to know how many bits does it take to get the number five and that is three bits; three bits total. So transition that back over. Our goal in this

00:07:44

step is to reserve the bits in the subnet mask and find your increments. So when I say reserve the bits in the mask, what I mean is I know that I can't get the number five with any less than three bits. And I know that network bits are ones so what I need

00:08:00

to do when I'm making this reservation is give myself three more network bits. So I pick up where the ones leave off and go one, two, three. Zero, zero, zero, zero, zero. Now I know, you're looking at this going whoa, wait a sec, that was a little weird. I'm not sure if I

00:08:20

follow that the whole way. Don't worry, we'll get used to this as we go through it again and again and again. But let me just reiterate our goal is to create more networks because we only have one. And we know that it takes three bits to get our five networks

00:08:37

that we needed and then partner that with we know that network bits are one bits it doesn't really matter that five was one zero one. I'm looking for three more network bits. So with that in mind I just add three more right where my network bits leave off left to right; one, two, three. At this point in the

00:08:55

problem we already know what our subnet mask will be for the entire organization. It is 255 -- convert this back to decimal -- dot 255; that's what this one is -- dot --.255; that's the third one. That's what we had originally, dot and then we need to convert this last octet right here back to decimal. Now again using those

00:09:19

skills from before if we line that back up to the binary chart that says we've got one 128; one 64; one 32; zero, zero, zero, zero, zero. So if I wanted to find out what this, right there, is in a decimal number, I would just take 128 plus 64 plus 32 and that, if we add that all together, will be 224. So our subnet mask that we get for our entire organization is 255.255.255.224. Now that's fantastic. We know what every single PC, what

00:09:58

every single router, what every single switch, every single device in our organization that is on the network will use this subnet mask. Woo hoo, you know, do the happy dance. But we don't know what that means yet, you know? Great we've got a subnet mask that's a key part of the equation, but we need to figure out what that subnet mask means and that's the second half of step two. Says reserve

00:10:20

the bits in the subnet mask -- we just did that, and find your increment. The increment, this is the other weird part, is going to be the lowest network bit that you have converted back to a decimal number. So look at our network bits. Right here, this is a 128, right? 64 and a decimal 32, that is our lowest network bit converted back to a decimal number, 32. That is our increment. So with that in mind, we can move to

00:10:54

step three, which says use the increment to find your network ranges. This is where the subnet mask becomes meaningful to us. So I just change my pen color here. Step three I'm gonna take what I started off with, meaning, the address that I purchased, 216.21.5.0. And then just begin adding my increment. Now my increment, right here, this 32 is in the fourth octet, so that's where I do my addition. 216.21 .5.32. 216.21.5.64. You can see all I'm doing here is adding my increment. 216.21.5.96 that's 64 plus 32. And so on and so on and so on we go. What this is when I'm looking at this, is the beginning of each network range.

00:11:54

Now, all I have to do is fill in the end. What's the last IP address before I get 216.21.5.32, which is this one right here. Now it's not a trick question -- 31 just taken one away from 32. Put this through, 216.21.5. -- last IP address before 64 is 63. 216.21.5.95 and so on and so on and so on we would go; down and down and down until we found enough network ranges to fit our organization. These are actual

00:12:30

reality to us. Meaning, let me -- let me do a quick sketch of that network diagram. The network diagram that organization had looks something like this, where we had three different networks that we were trying to address. Now what I can do is I can start assigning these network ranges to that organization.

00:12:49

This one we'll address, I think this was Arizona that I put -- the Arizona router and they will use that range for this network right here. You can see what we've done is sacrificed the total number of hosts we have or to -- to get more networks. We originally had 254 hosts with our Class C address up here. And now we've

00:13:10

sacrificed that and said, well, I'll have less hosts, but more networks. The second network range can go ahead and address, I believe this was California down here and the third network range we'll address Florida up there in the upper right-hand corner.

00:13:25

I won't draw the arrow across, just so it doesn't get too messy. The fourth network range would address the WAN link. And the fifth network range -- I didn't go that far because I ran out of space down here, but the fifth network range would address that WAN link right there. Those are the network

00:13:39

ranges that I can assign to the devices. I would then assign IP addresses from these ranges to the computers in Arizona and assign IP addresses from this range to the computers in California. This is the meaning of subnetting; breaking our one network into multiple networks. We've got our new subnet mask that we use

00:13:58

and our network ranges that can be assigned to the different devices. With that in place, I know, at this point it's like, okay, I'm seeing that; still a little fuzzy. Let's do another example. Network scenario number two. Instead of drawing this massive

00:14:16

network, I just put our requirements in the upper right-hand corner. We have another organization that is using 195.5.20.0. It's a Class C network. And they need to break that one network; 195.5.20 into 50 sub-networks or 50 smaller networks. It's a lot of networks; that's why I didn't want to draw a network diagram.

00:14:38

So let's work through the steps again. Number one, determine the number of networks and convert that number to binary. 50 is how many networks we wanted. So I'll put our equals and let's draw up our binary chart. 128, 64, 32, 16, 8, 4, 2 and 1. So 50 networks; zero, zero, one, I can take 50 minus 32 and that would give me four -- eight --18; so, 18 left over. So I'd have a 1 and a 16 that would leave me two -- 18 minus 16, so there's our two and that is our binary number. Zero, zero, one, one, zero, zero

00:15:24

one, zero. Now let me ask you a question. How many bits does it take to get the number 50? Well, looking -- looking at this number I can just underline where the first one started and say that takes one, two, three, four, five, six bits. Good, because we're going to need that number when we do step two.

00:15:47

So step two now says reserve the bits in the subnet mask and find your increment. Again, don't skip this first part. It may seem tedious, but that is the key to seeing what bits you have to work with. Our original subnet mask is Class C, so in binary it's 8 ones dot one, two, three, four, five, six, seven, eight ones dot one, two, three, four, five, six, seven, eight ones dot and then the most critical piece. Not all the ones, it's the zeros; one,

00:16:20

two, three, four five, six, seven, eight because the zeros is where we can do our subnetting. We were given a Class C address so we can't change any of those first 24 ones right there. We can only play with the last eight zeros. So now we look at our requirements, it says reserve bits in the subnet mask and find your increment. Our organization wants to break this into 50 sub-networks. We know that it takes six bits to get the number

00:16:46

50. And we know that ones are network bits. We need to change our subnet mask to where we have six more ones. So we do that; one, two, three, four, five, six. And the other two can remain zero zero, zero. We've stolen six network, or six host bits and made

00:17:06

them network bits to meet our requirements. Just like that, poof. We know what our subnet mask will be for our whole organization. It's 255.255.255 dot, and then we need to convert this last one back to decimal. So we use our binary to decimal and decimal to binary conversion skills and I say I've got one 128; one 64; one 32; one 16; one 8; one 4; no twos no ones. So I can, by the way when you see this you can approach

00:17:41

it one of two ways. I can either add all these numbers together 128, 64, 32, 16, 8, 4, 2 or four, add all those up and I would end up, if I did that addition with the number 252. But that's a pretty long addition problem, adding all those values together. So one of the ways

00:17:59

that I do this and find a little shortcut is I know if all of these are turned on to one, it's what number? 255; right? That's -- that's the maximum number I can get. And I can look at this and go, oh, well, there is no twos and there is no one, so I can just do 255 minus two, minus one or just add those together and just do 255 minus three and get 252. So whatever way works easier in your mind for you, either doing addition, adding all those together or knowing the maximum is 255 and just subtracting what's not turned on. That will give you your subnet mask. Now

00:18:37

I'm trying to think should I add another piece at this point? No, I'm not going to. Let's -- let's keep working through this, I'll add it once we're done with this problem. It says reserve the bits in the mask and find your increment. So we've got the mask, we've reserved the

00:18:49

bits, our increment is the lowest network bit, that guy, converted back to a decimal number. Now if we look in -- in binary, this is or in decimal, this is one, two -- that one is a four. That is the decimal equivalent of the lowest network bit. That is our increment and that is what we need to find our network ranges. So the last step will be finding our network ranges.

00:19:17

We start with what we were given; 195.5.20.0; that's the address that we purchased from the powers that be. And we want to use to address our whole organization. So now I just need to start adding my increment in whatever octet it's in. I notice that it's in the fourth octet right here. So I'll just

00:19:36

do some simple math, 195.5.20.4; 195.5.20.8; and I'll just start shortening --.20.12;.20.16. You know this is the same the whole way down. That is the start of every single network range that I have. Now let's fill in the end. I'll go back to the top. The last IP address before I get

00:20:02

to 195.5.20.4 down here is.3. The last IP address before I get to 195.5.20.8 is.7 and down and down I go;.11 is the last one before 12;.15, you know, same thing. 195.5.20.11;.15 and so on. I just keep on going. I think the next one would be.19 because.20 would be if I added four over here. And I would just keep finding all these network ranges. Now let

00:20:33

me fill in a little more -- a little more information here about these network ranges. We've taken one Class C network, 195.5.20.0 with one network that could go all the way up to 255 and broken it into all these little sub-networks. Now there is a price to pay

00:20:55

whenever you do subnetting. Here it is. When we had one network, we couldn't use the very first or the last IP address; right? Because the very first IP address identified the network. It's known as the network ID. You can not assign 195.5.0.20 -- or .20.0 to a PC or to a router or to any device because it identifies the network. We can't assign that IP address because

00:21:19

that's the broadcast. Meaning, if I wanted to send a broadcast to everybody in that network, I would send it to that IP address. So I can not assign this IP address to any given host. Now what we've done is taken this one network and broken it down into mini sub-networks. But when we do that we can not use the first

00:21:42

IP address or the last IP address from every single network range. So I can not assign 20.3 to a host because it's the broadcast for this first network right here. I can not assign 20.7 to a host because that's the broadcast for the second network and the third network and the fourth network. I can not assign the first or the last IP address from

00:22:05

every single range to a host or a router or a switch or any device on that network. So what does that mean? That means when I really look at this, I have one through two; five through six; nine through ten. I have two usable hosts per network that I can actually assign -- one and two; five and six; nine and ten -- that I can actually give to a device. Now I know you might be looking at

00:22:32

that going, that is stupid he-he. Why would you ever have a network of two hosts? Now with that being said, I can tell you that is the second most popular subnet mask in the world. I'm not kidding. This subnet mask that you just found 255.255.255.252, which gives you two usable hosts per network is the second most popular one in the world because it's perfect for those kind of networks right there. That is considered

00:23:09

a point-to-point WAN link, meaning, you know, this -- I mean think of the diagram we had before where we had, you know, we've had some hosts over here and some hosts over here. And I said but this is a network, too. Well, that network will never have more

00:23:24

than two hosts per network because there's only eight points. I'll put.1,.2, to point network right here. So I can assign this first network to that point-to-point WAN link. I have another point-to-point WAN link right here. I could assign this second network, maybe.5 is assigned to that router right there. And.6 is assigned to that router interface over there. That is a very popular subnet mask and very popular way to find network ranges for your WAN links. Now

00:23:55

with that being said, that is the second network scenario that we've gone through that is a Class C address. I'd like to add one more piece of information that we can gather from this. That is a different way to write the subnet mask. You can see that I have the Class C subnet mask right here, 255.255.255.0. Now I don't know if I've written it this way in the past in this series, but you'll see this subnet mask, short-hand abbreviated, a lot of times a /24. Have you seen that before? When -- when people write a Class C subnet mask up here, they might write it 195 -- oops, 195.5.20.0/24, instead of actually writing 255.255.255.0; that's known, technically known as cider notation. Many people call it bit notation or slash

00:24:49

notation. There's a lot of names for it, but all it is shorthand for writing the subnet mask. And now that we have this problem sitting right in front of us, we can explain why this shorthand notation means the same thing. When you see slash and a number, that is literally the number of ones in the subnet mask when you convert it to binary.

00:25:11

Ha, seriously, look at this. Class C subnet mask -- 255.255.255.0. If you converted 255 to binary, how many ones is that? Eight, same thing here, eight, same thing there, eight. So if I take all of those ones and add them up, 8 plus 8 plus 8 is twenty four. It's shorthand. So if I were to look at a Class A subnet mask; that's

00:25:33

255.2 -- oops, or.0.0.0, that is abbreviated as a /8. A Class B subnet mask 255.255.0.0 is abbreviated as a /16. Class C is /24; that's the bit notation. You're just looking at how many ones, 8 plus 8, or just 8 up here is in the subnet mask. And the same thing works for these custom subnet masks right here. 255.255.255.252 can be shorthand notated, in cider notation or bit notation by saying, okay, we've got 8 - ones there; 8 - ones there; that's 24, 25, 26, 27, 28, 29, 30. /30 is shorthand bit notation for 255.255.255.252. When you are working on a CISCO device, there are many show commands that will show you the subnet mask in that format and there are many show commands that will show you the subnet mask in that format. So you need to be comfortable working with both.

00:26:41

Same thing if you're preparing for the CCENT or CCNA exam, there are questions that will give you the subnet mask in both formats, one or the other. So you need to be very comfortable working with either one. So what I want to do as we work through these

00:26:55

problems, we've got two more scenarios that I've got for this video that I want to work through, I want to show you the subnet mask both in decimal and bit notation so you can get comfortable working with the either. Now before we move on to network scenario number three, I wanna make a quick point. We just did two back-to-back network

00:27:15

scenarios that are using Class C networks. I'm about to move into a Class B example. Now don't worry it's the same thing. It's the same three steps, same process that you work through. But I want to make sure before you jump into this one that you are comfortable with the Class C examples we just talked about. So if you would like, what I would propose is to pause

00:27:37

the video right here, if you're still feeling like you -- you wanna see those again, rewind it and do the Class C examples one more time. That's the beauty of video; just watch -- watch me work through those two Class C examples, then come into this Class B. If you're feeling

00:27:50

comfortable and -- and you're ready for a Class B example, feel free to keep on watching. I just wanted to make sure I mentioned that we are moving into another class of problem if you will. So here's our scenario, we are given a Class B network, 150. 5.0.0 and the organization that we're working for has offered us a lucrative $16.3 million contract to break that into a hundred sub-networks. As of right now, you

00:28:20

know, Class B network 150.5.0.0; 255.255.0.0. We've got one network; that's 150.5 and a whole bunch of hosts. 65,535 I believe to be exact. And that -- you know, that's way too many hosts. We want to break that into a hundred different sub-networks; that's our goal.

00:28:42

So the process is the same. Number one determine the number of networks and convert to binary. 100 sub-networks; right? That in binary -- let me just write up our chart. 128, 64, 32, 16, 8, 4, 2, 1. So we convert it to binary; zero -- we can't subtract 128, so our first one goes right there. 100 minus 64, remember on CISCO exams there are no calculators. So that will be 9, -- six 36, right? So we can take our 32, that would leave us with four. Zero, zero, one, zero, zero. So a hundred as a binary number

00:29:23

is 01100100. Now, let me freeze for a moment right there. I'm not all about teaching shortcuts. Meaning, you're going to find as you work through more and more examples, there's ways to -- to cut time by doing shortcuts. But there is one thing I do want to

00:29:44

show you and that's how to save a little extra time right here. When I convert 100 to a binary number, remember I'm not so much after the binary number itself as I am after how many bits did it take to get to the number 100, right? Because that's what I'm wanting for the second step of the problem; that's why we do this binary conversion to start off with is we want to know how many bits it takes to get to the number 100. Now as soon as I find where my first one goes, do I know how many bits it's going to take? Well, sure I do. Soon

00:30:16

as I know that my first one is 64, I know that I'm going to have one, two, three, four, five, six, seven bits. It doesn't matter what the rest of the binary, you know, comes out to. I know as soon as I know where that first one is that it takes seven bits to get the number 100. So a time saving shortcut right there, as soon as you look and find out where your first one goes in the binary equation, you can stop. You don't have to figure

00:30:44

out and do subtraction and find the rest of it because you know, stop right there as soon as I know my first one is at 64, it takes seven bits to get to the number 100. That shortcut helps you save some time, it's great. If it confuses you, forget I ever

00:30:57

said it. Just figure out the whole binary number. But you'll get comfortable with it as you work through it a couple more times. Here is the second set, reserve the bits in the subnet mask and find your increment. Now again, it becomes even more critical when you have a Class B example to write your subnet mask in all binary one, two, three, four, five, six, seven, eight. That's our first.255 Eight, there's our second.255, now the host bits; one, two, three, four, five, six, seven, eight dot one, two, three, four, five, six, seven, eight. We have 16 network bits, it's a /16 subnet mask by default and 16 host bits that are at our disposal. Now we're going back to our question. We want to take the Class

00:31:42

B network and break it into a hundred sub-networks. We know that it takes seven or sorry, six bits to get the number 100. So we will pick up right where our ones leave off. This is the key don't -- don't start it's not a Class C example anymore. Don't start adding ones over here. We pick up where the

00:32:00

ones leave off and say I need -- wait a sec, did I say six bits or seven bits? Seven bits; seven bits to get the number 100. Sorry; one, two, three, four, five, six, seven, zero dot and all these stay zero -- zero, zero, zero, zero, zero, zero, zero, zero. Eight zeros.

00:32:18

There it is. Okay, 8 zeros. That is our new subnet mask when we're using a Class B example. Remember it's the same as it was before, it's just now we're working in this third octet, rather than the fourth because we started with a different subnet mask. So our

00:32:31

new subnet mask, we now know that is 255.255. -- if we were to convert this one back to decimal, we could either add all those up or just know that it's 255 minus -- we don't have a one. It would be 254.0. So our new subnet mask is 255.255.254.0. Or if we're writing it in slash notation, it would be a /23. We had an original 16 bits -- eight and eight, right there. And we just added seven more; that's

00:33:03

the 254 or the seven bits right here. So you can just think of that as a /23 as shorthand notation. So that's the first part of step two, reserve the bits in the subnet mask and now find our increment. Our increment is the lowest network bit converted back to a decimal. Now don't

00:33:22

start letting your mind go wild here, because I know you might think, okay, well, 128's right there, so is this like 256 now and stuff like that? No, the increments restart every single octet. So it's very simple; this is a one. This is a two, four, eight, you know, the decimal. I'm looking

00:33:41

for the lowest network bit converted back to decimal number, that is simply a two. Now, step three; use the increment to find our network ranges. Just like the previous example, we're gonna write 150.5.0.0; that's the network that we started with and now we just start adding our increment. But before I do, I

00:34:03

gotta ask the question what octet is the increment in? The third, right? This -- this octet right here is where our increment is at. Before when we were doing the Class C example, our increment was over here and that's why we added the number to our fourth octet.

00:34:17

But since now our increments in our third octet; that's where our addition takes place. So we have 150.5.2.0, 150.5.4.0;.5.6.0; .5.8.0; forgive my penmanship getting a little sloppy as I go down. It's 150.5 the whole way down and so on and so on and so on. We just

00:34:41

keep adding to -- to that number. Now we fill in our end range and this is where it gets a little tricky. You look at this what -- and ask the question, what is the last IP address before I get to 150.5.2.0? Well, you look at it and go 150.5.1, and be careful right here because I know you might be thinking well, 1.0; right? Well, remember if we do 150.5.0.0 through 150.5.1, if I put a zero right here, then that's where this first range ends and the next one picks up at 2.0. So let me ask the question what happens to the number 150.5.1.50 or 150.5.1.51; 52; or 53? What happens to all of the 150.5.1 numbers? Well, if you go to 150.5.1.0 as your end, you lose all of them. You can't -- can't do that. Think of some weird twisted

00:35:39

math problem, 150.5.2.0; that's where our next one starts, if we were to subtract one from that, the last possible IP address before we get to 2.0 is actually 1.255. Ah-ah! This one goes through 150.5.3 -- that's the last one before we get to 4.0.255. Again, last IP address before we get to four is 3.255. Last IP address before we get to 6.0, 150.5.5.255 and so on and so on and so on we go.

00:36:17

Does that make sense? It's kinda weird, but that's -- that's the last IP address before we get to two and four and six and eight and so on and so on. It is going to be the 255 because that's how the binary works out. That is the answer to the problem. Now there's a couple more

00:36:32

pieces I want to add as we have walked through this problem. The first one is this, as you look at these network ranges, we now have a network range that shows 150.5.0.0 through 150.5.1.255. We know that we can't use the last IP address from that range, right? 1.255 because that's the broadcast, just like we saw on the previous one. We can't use the first one from each range either because

00:36:58

that identifies the network. So those are unusable. Now here's the question, I'm looking at that first range; that's where my arrows drawing from, somewhere within that range I'm gonna run into the IP address 150.5.0.255, right? Do you see that? It's somewhere squished in the middle of that range. Can I actually assign that to a PC? Hmm.

00:37:25

Well, on that same token before I answer that question, I'm also going to run into 150.5.1.0 somewhere in that range, you know, it's in between 0.0 and 1.255; that's -- that's an IP address in that range. Can I assign that one to a PC or to a router? The answer on both accounts is absolutely yes, you can. It's

00:37:49

going to feel really weird when you're typing it in because we're -- we're geared in the decimal mindset. We're -- we're geared to think, oh, 255 you can't use that. That's -- that's a broadcast, right? You can't use that. And same thing with 1.0, you can't use that. You can't use zeros; that's -- that's the network.

00:38:05

That's thinking in a decimal mindset. Those addresses are right in the middle of this range. They are completely valid addresses. Like I said it's going to feel really weird typing it in, but when you combine it with this subnet mask in your network properties field, it will work just fine. It's right in the middle. There's

00:38:26

only one broadcast address and one network address for each range and that is it. We circled them right there on the screen. Everything that's in that squishy oreo center of that works just fine. That's something to get used to. And then I want you to already

00:38:41

begin envisioning, if you're preparing for the certification exam a test question that says, which of the following addresses are valid and invalid; select all that apply. Well, when you see this you think, oh, that's invalid. Well, that's not true. You have

00:38:57

to back up and say, well, what subnet mask are we working with, first of all. Based on that subnet mask, you'll be able to figure out which ones are valid and invalid. So that's the first piece I wanted to add to this is getting comfortable with those network ranges. The second piece that I want to add to this is what

00:39:15

if -- what if somebody really wanted to know, you know? Okay, I can see that, you know, we wanted a hundred networks, but, you know, how many networks did this really give us? I mean, if we were to come up, here's one, here's two, here's three -- you know, if I wanted to know how many networks I could get using this subnet mask. Is there an

00:39:34

easy way to do that without adding all of these up, you know, going through and writing all the ranges and then adding them up one by one? Well, the answer to that is also yes. We can figure that out by using a formula. And I know this is the first mathematical

00:39:48

formula we've introduced here; it's known as the power formula. Two to the power of X is the formula that I want you to remember, where X is actually the number of subnet bits. Now if we look we added one, two, three, four, five, six, seven subnet bits.

00:40:07

That's what we found right here. It takes seven bits. So if we do two to the power of seven that will tell us just how many subnets we're going to end up with if we were to count this all to the bottom. Now that's -- that's a painful equation when you're on a certification exam and don't have a calculator in front of you. So let me -- let

00:40:31

me do this, let me show you two things. First off, I want to show you how to figure this out if you have a calculator and second, I want to show you how to figure out if you don't. If you have a calculator, let me bring this back into the screen; just clear off what we've got here, if you have a calculator the Windows calculator, all I need to do is go two, then move over here to these fuchsia numbers, x^y will do two to the power of seven and hit the equal sign and that will tell us exactly how many networks we get. If we

00:41:05

were to follow this all the way to the bottom, we would end up with a 128 -- oops, I went out of the screen -- a 128 different subnets that we could break this into. That's the way to do it with the calculator. If you don't have a calculator, the way to do it is using your binary chart.

00:41:24

You might remember when I talked in the binary conversion video, I said these are actually the power of two. This one is two to the power of zero. Remember I said I don't know why two to the power of zero is one, but it is. Anything to the power of zero is one.

00:41:37

So if you remember that, you can go okay, two to the power of one is two. Two to the power of two is four, three, four, five, six, seven. Ah-ha -- is 128. So I can look at two to the power of seven and say that is a hundred and 28 just by looking at my binary chart and realizing they're powers of two.

00:41:57

Okay, are you comfortable with that? That is adding a couple of pieces to this, finding out that in between these network ranges we have some odd numbers that are valid and finding out the way that we can find how many networks we really get when we do subnetting. Using that same logic,

00:42:16

let me just clear up some room -- I'm looking at this -- this screen right now, thinking how on earth can you learn anything from this mess? It's just a mess of numbers at this point. So let me just carve out a little extra space out for myself so I can do some writing here.

00:42:32

I just showed you the equation, the two to the power of X equation to find the number of networks. But what if you were asked not -- not for the number of networks, but how many hosts do I get in each one of those networks? Meaning, how many hosts do I get in between 150.5.0.0 and 150.5.1.255? Well, just looking at that, it's not very easy to just add those up and -- and figure that out. So you can use that same equation, slightly different to

00:43:02

find the number of hosts. Two to the power of X, but this time X is how many zeros. We were using ones the find how many networks we get, so two to the power of X with zeros being the X this time will tell us how many hosts we get. But remember we have to do a minus two on there.

00:43:23

We have to subtract two from whatever our value is because we cannot use the last nor can we use the first IP address from each range; that's why we subtract two. So in our case, two to the power of X, X is one, two, three, four, five, six, seven, eight, nine zeros. We have nine zeros left over in our subnet mask.

00:43:44

So two to the power of nine minus two will give us that equation. Now again, if you've got your calculator that makes it a lot easier. We can go two; x^y -- this fuschia one, nine equals 512 minus two, 510. So there are 510 hosts per network here. If you don't have a calculator

00:44:08

in front of you, you can say okay, well, I know two to the power of seven is 128, you know? You know where that leaves off. So two to the power of eight is 128 times two; that's 256. Two to the power of nine is 256 times two and that is 512. It will take a little extra math if you don't have a calculator, but that will be able to tell you how many hosts per subnet you have.

00:44:36

All right. I have one more network scenario to work through with you. And after seeing the Class B one, it shouldn't be to bad, although, I've thrown in an extra little twist in here. We now have a Class A example. We have the network 10.0.0.0 and we would like to break that into 500 networks. Wow. All right. Same three steps; same process, just a little bit bigger

00:45:02

numbers. We've got step one, determine the number of networks and convert to binary. So here's my hint for this one -- 500 is let's go ahead and write our binary table. 1, 2, 4, 8, 16. 32. 64, 128. Now stop right there, because I know that -- wait a second, I -- I can't get the number 500 with eight bits. I can only get 255; right? Right. So we need to keep going, 128, 256 -- I'm running outta room here -- 512. Now, immediately I look and I go, oh 512 is bigger than 500. So I at -- my first one doesn't go there, I can't subtract 512 from 500. So my first one goes erk -- right there; 256. Now I can work that out and do 500 minus 256 and -- and find the whole binary number for what 500 is. But remember I just mentioned on the last slide, we're not after that binary number and exactly what it is. We just want to know how many bits did it take to get the

00:46:06

number 500. And when I look and I go, oh, well, my first one went right there. I immediately know it took one, two, three, four, five, six, seven, eight, nine -- nine bits to get the number 500. Good? All right, second step, reserve the bits in the subnet mask and find your increment. Again, we now have a Class A network, so I need to

00:46:31

write that subnet mask in all binarys. 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 one, two, three, four, five, six, seven, eight. Trust me, it doesn't

00:46:49

take you this long when you're not talking as you do it. It just -- it's hard to write and talk. So we have to 255.0.0.0 written in all binary. I now need to ask, am I trying to get more networks here or am I trying to get more hosts per network? Now I -- I look at that and I say, well, I want more networks. Now I asked that

00:47:07

question because in the next video I'm gonna show you the second style of subnetting, which is host per network. So we say I wanted 500 networks. 500 networks need nine bits and I know network bits are the ones, so I'll pick up right where the ones leave off and go one, two, three, four, five, six, seven, eight -- eight bits per octet -- dot nine. One, two, three, four, five, six, seven dot and then those all stay

00:47:35

zero. So we actually bled past our octet. We moved into another octet. So I know my new subnet mask is 255. -- second octet is now 255. -- now, if I convert that third octet to binary, what is it? Or wait, to decimal? It is 128 as a decimal number. One, zero, zero, they're all zeros.

00:47:56

If we line that back up; that's 128. So that is our new subnet mask or in bit notation it's / -- we have eight - ones; eight - ones; that's 16, 17. /17 is our subnet mask. Wow; that's new. Now, here's the unique part about it, what is our increment? Lowest network bit converted back to a decimal number. Well, that network bit is

00:48:21

128. Wow. weird, So our increment is the same as our subnet mask. You bet it is. So now we have all the pieces that we need to move on to step three and find our network ranges. This is where it's going to take a slightly different look, but like I'm doing it, I'm adding more pieces on every single one of these problems. This is the last piece I need to add. So we

00:48:43

have the increment to find our network ranges. We started with 10.0.0.0 hang on, let me get a different color here. I know -- I know. Colors don't matter but to me they do; they stand out better. So 10.0.0.0 is what we were given and what we started with. Now we need to look back at

00:49:02

this increment and identify what octet the increment is in. It's in octet number three. So I can just go and add 128 to the third octet. 10.0.128.0 10.0. -- wait a sec, what happens if you add 128 to 128? 128 plus 128, that gives you 256. You can't have 256 in an IP address. Well, here's -- here's where I want to show you. Now notice

00:49:38

first off we added eight network bits. I know we're going to get way more than two network ranges with eight network bits. I mean, if we did two to the power of X where X is eight, we get a whole bunch of networks that are at our disposal with this; at least 500. So I know that I can't stop right here, so let's fill in the end ranges. Just kinda -- erk -- draw a line. Let's -- let's see where

00:50:02

things end. This would go, what would be the last IP address before we got to 10.0.128.0? It would be 10.0.127.255, right? This would go through 10. -- well, let -- let's do the math as if it worked, right? Let's say that this went to 256.0, right? If we were just adding like we were before, what would be the last IP address before we get to 256.0? 10.0.255; that's the last one before you get there, right?.255 But we know that we can't have 256, so let's -- let's make a slight correction here.

00:50:48

Erase that. When we have 255.255, if I were to do like a plus one -- think of this as, again that weird twisted math problem. I know that I can't go to 256, so this will be that'll zero it out, right? 255 plus one and carry the one. So we have a plus one there. You can't have 256 so zero it out, carry the one and now I have like this 10.1.0.0. Hmm; that's exactly what the next range starts at. 10.1.0.0 and then just keep adding our increment. 10.1.128.0. 10 -- instead of doing this all over again, I will now recognize it and go, well I can't have 256 so we move up to 10.2.0.0. Let's fill in some end ranges here. 10. -- this will be 10.1.127.255; that's the last IP address before I get to 10.1.128. This goes through 10.1.255.255. Last IP address before I get to 10.2.0.0. And so on and so on and so on we would go down and down and down the range; that's a tough one. I have

00:52:02

to tell you, that's -- it takes a little logic and a little working through that to get it, but that is how you can find those network ranges is just identifying where the next one starts and subtract one to find where the last one would end up ending. Before we end this video, I want to make sure that you get some practice because doing subnetting, working through it again and again and again and again and again and again and again, is the only way that you're going to solidify this skill yourself. So what I have here

00:52:31

is four problems to do on your own. I have two Class C examples, which are by far the most common subnetting styles. But then I have a Class B and a Class A example as well. And they do have their own little twist break into a thousand networks; break into 25 networks and that sort of thing. So I want you to take some

00:52:49

time, grab a piece of paper and work through these problems so that you can make sure you can not only observe this skill being done on the screen, but do it yourself. Now I know that examples or -- or practice problems without being able to know if you're right or not are of no use, so what I've done is I've actually worked through these problems on my own, and put up my results on NuggetLab.com. You'll actually see a file there

00:53:13

named something like CCENT support files or it'll have some identifier that you'll be able to quickly CCENT something. And you can download that and you will be able to check your work and verify your answers. When I worked these out, I worked them out on -- I just did it in a Microsoft Word document. I saved it as a PDF

00:53:30

file, so everybody can open it. And all I did was -- was walk through the three steps. So I have the results of the three steps that you would be walking through, you can compare your answers to mine and make sure that you're on the right track. This is the first

00:53:44

style of subnetting that we must master before you move into the next style in the next video. I know that this video has been a little extra long compared to the traditional CBTNuggets video in this series, but I couldn't think of a better way to group everything together and show you enough examples where you can see at least four different scenarios working through different classes of subnetting, based on the number of networks. The benefit is you now have the chance

00:54:10

to just sit down, let it soak in, review this video; review just sections of this video multiple times if you need to see some examples as you work through those practice problems. I'll also mention that when I created those practice problems, I didn't pull them from the book or something or -- or what -- what should I do? I just made them up and you can do the same thing. Don't -- don't think that

00:54:31

those four practice problems are the only ones that you can do. Just think of a -- a network that you have, you know, 172.16.0.0 and then just say I want 50, 90, 100 different networks and then work out that subnetting problem. And figure out what the result will be. The key is not only to master

00:54:51

the subnetting, meaning, come up with the subnet mask and find your network ranges, but to be able to do it quickly. I'll talk more about why that's essential in the next video. For now, I hope this has been informative for you and I'd like to thank you for viewing.

Advanced TCP/IP: IP Subnetting, Part 2

Advanced TCP/IP: IP Subnetting, Part 3

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Jeremy Cioara
Nugget trainer since 2003