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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.

All trademarks and copyrights are the property of their respective holders.
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

Advanced TCP/IP: IP Subnetting, Part 2

Advanced TCP/IP: IP Subnetting, Part 3

00:00:00

Alright, it's the final piece IP subnetting part three. And thankfully this one's not that difficult at all. It's considered reverse engineering subnets. Up to this point we've talked about how to subnet based on the number of networks. Based on the number of hosts and now we're going to look at working it backwards reverse engineering subnets. Now as I mentioned

00:00:22

in the previous video this is the most common style of subnetting you're going to find in both the real world and in the certification exam. It's essentially a type of subnetting that says here's the answer, now work backwards. We'll finally wrap up the whole

00:00:39

subnetting section by talking about the great exception to the rule and I'll explain that once we get there. So let's get going with the reverse engineering. Here is a perfect example of reverse engineering a subnet problem. We have a host or a router or a switch on our network and we look at it and get this IP address information.

00:01:01

We see it's IP address and we see it's subnet mask and we're faced with the question of is this IP address even valid? What network range does it belong to? Or you know, what network is this part of? Is it on the same network as the other hosts that are plugged into the same switch and all that. All of these questions are

00:01:20

honing in on the reversed engineering. Meaning we see the IP address and we see the subnet mask and we want to know what network range that IP address belongs to. So when you're faced with a problem like this and you're trying to figure it out we need to work backwards and in my mind it's a little easier than the ones we've been doing up till now. The number of networks

00:01:41

and the number of hosts. We don't have to do any of the conversion to binary of those numbers and reserving bits and so on because we have the answer. This is the answer. Somebody figured out the subnet mask for this host way back when and in that subnet mask lies the key.

00:01:58

We want to know what increment was used when we figured this all out. Meaning this IP address right here belongs to a range and the only one way that we can know the network range is to reverse engineer this. Work backwards and figure out what was the increment. The way we do that is take the lowest subnet mask

00:02:18

AC Tech or the non 255 subnet mask and break it in to binary. So 224 in binary if we were to lay out our binary chart 128 64 32 16 8 4 2 1 224 is actually one one one zero zero zero zero zero. Now you can subtract that out and work with it, but after you see the subnet mask values for you know, so long you're going to start going, oh, that's three ones. Now what increment was used with that subnet mask? Well,

00:02:53

the lowest network bit that one so it is 32. So 32 was the increment that they used when they found these network ranges so we'll start where they had to start when when this subnetting was reversed engineering and when I say they I mean the network designers or whoever planned this scheme. So I put 192.168.1.0 and just start adding 32. 32, 34, 96, 128. And we could keep going but we've passed the IP address so we can work backwards and find out, oh, this is the network range that they came from. 192.168.1 through, oops, 127. You can still see it. That's the network range that we're working

00:03:45

through. Is this IP address valid? Absolutely not. At least not to be assigned to a host because that is the last IP address in the range which makes it the broadcast address which the only way that you'd be able to figure that out is by doing reversed engineering and seeing the error of assigning that IP address to the host.

00:04:06

Let's move on to scenario number two. Once again we have an IP address assigned to a pc 172 16 68 65 We've got the subnet mask listed below and a default gateway is assigned, 172 16 68 62. IP address down here of the default gateway is 172 16 68 62 looks good that's going to be the gateway the computer uses as it goes out. And we see the subnet mask of the default gateway

00:04:33

is the same. Everything looks good and maybe down here is the internet. Now this scenario might be a typical test question. It might be a scenario in your network environment. Either way, the only way you're going to know if everything is kosher on here is by doing the reverse engineering. So once

00:04:52

again we'll look at the subnet mask because therein lies the key. We see 255 255 255 240. If we were to break 240 into binary I should just have a template that I paste up here on of my binary numbers. But get used to writing them. 240 in binary is one one one one zero zero zero zero. So

00:05:18

there's our binary value, which means our increment at some point must have been lowest binary value 16. So when the designers of the network put this together they decided 16 was their increment. Well, let's figure out and see if we can find what's wrong with this picture or if everything is right. We've got 172 16 68 0 where we'll begin, and just start adding 16. 16, 32, 48 64, 80, if we add 16 and we're good, we've passed both those numbers. Now, before we look back at this scenario you may wonder well, isn't this a class b network to start off with? Shouldn't you have started from 172 16 0 0. zero. Well I guess you could have, because whoever subnetted

00:06:10

this out initially probably started there. But the catch is that when you're incrementing by these values you're always going to loop back around. Meaning if I started from one seventy 172 16 0 0 and started adding 16 and that for AC tech, I'd go all the way up to 256 and then go plink, 172.16.1.0 dot one dot zero. Over here. And then we add up of all the values

00:06:35

to 256 and then go to 2.0. So the point is that you would eventually reach 68.0 by counting by 16 you just take a lot more paperwork to do it. So instead we can just start from the zero in the last AC tech where this this network range would have started. And if you look

00:06:53

we passed both of these IP addresses. 65, well, that one shows up right here and 62, that one shows up right here. So wait a sec, we have a major issue. This pc is assigned an IP address in a different network than its default gateway. It belongs to this network range

00:07:17

172.16.68.64 through 79 that's where the pc is at, and the router is at the network range above it. That's a big problem. Pc's even if they're plugged in to the same switch like this one is to the router. If that device is on a different network it will not be able to reach it. It's

00:07:35

it's not going to know that that device is reachable because when it compares its subnet mask and it ties this all together the pc goes wait a sec, my default gateway is not even on my network, it must be somewhere else. Meaning I would need a default gateway to reach my default gateway. If this

00:07:52

this is how it would all work out. So this would indicate a communication problem. This would be the breakdown. And now you can see why this is the most common style of subnetting not only on the exam because it's very easy to embed something like that into a much bigger question. You know, a scenario might say

00:08:08

oh you know PC A here can't access the internet. And there will be a bunch of other scenarios in here of routing tables and protocols and blah blah blah, to try and throw you off. But really they're just not on the same network at all. They're not in the same range. Same thing

00:08:22

in the real world. You'll need to know if devices are not on them same network because that's where you need a router between them in order for them to access each other. The way we would fix this is maybe over here the router's connected to another ethernet network with some PCs. And over here maybe this

00:08:40

IP address is assigned the dot 62 but this interface would need to have an IP address from the same network range that this host belongs to. Some, you know, maybe dot 49 would be valid for this one. So host A can reach it and get through that router to another network. That's what routers

00:09:01

do is bridge networks and connect them together. So at this point we've seen all three styles of something that you can have. Figure it out based on the number of networks. Based on the number of hosts, and reverse engineering. I want to mention one more document that I've created for the series and that is also available on nuggetlab.com. I realize

00:09:23

that, you know, many of you may have been going through the examples at the end of every chapter and a lot of times it is good to just have some practical examples sitting in front of you that you can work off of without needing to go through the whole video to to relearn the whole process. Let me show you

00:09:40

what I mean and this will make a little more sense. I've created a document it's in pdf format. Let me see if I can shrink it down a little bit more there we go. Pdf format right on the website. It is subnetting examples. What I have is in a text document there are three types of examples that I'll show, one based on the number of networks one based on the number of hosts, or host per network or clients. And then also an example

00:10:04

of how to reverse engineer it. So what I've got is you can see subnetting style one, subnetting based on the number of networks. And I tried to, as well as I could, walk through my thought process on paper when i'm working through. These kind of like a when I was talking

00:10:19

through them in the videos that's that's my thoughts. And this is kind of me writing my own thoughts. You know, we've got a service provider given this you must break it into 20 subnets, so step one determine subnets and convert to binary. So there it is. Second step reserve the bits in the mask and find the increment

00:10:35

and we can see the binary tells you how many bits your regional subnet mask is this so that's our original subnet mask in all binary we must convert five of them to network bits. So you can see what I did was try and write what my thoughts were in paper so you can always print this out and refer to it in any time. I did one

00:10:52

subnetting style one is an example based on the number of networks with a class C range. The second one is based on the number of networks or subnets with the class B range because I wanted to give you a feel for each style. Class A is you know just like class B so I didn't really include one of those. We have style

00:11:12

number two right here based on a number of clients. And then style number or sorry example number two and is based on the number of clients with a class B address. So I did a class C and a class B for each one of them. And then finally I have subnetting style three which

00:11:27

is given an IP address and subnet mask find the network range. That's the reverse engineering that we just worked through and that you've got a full example of how that works as well. So I really encourage you to download that, Print it out, review ita couple times. It'll kind of solidify everything that we've been

00:11:43

talking about in one place. There is one more thing that is in this document and that's what I want to talk about right now. It is what I would call the great exception. At this point you've probably seen enough examples to get a feel for how this works. Meaning, how the process of subnetting

00:12:02

works. When I say oh we've got 30 hosts per network and I say our first step is to break that in to binary, the reason that i'm doing that and I'm converting 30 to binary is because I want to know just how many hosts per network I'm going to need. I think that's the number for 30. I was just doing that while I'm talking and if that's right I must be really good.

00:12:25

But it's probably wrong so my my thought is that you know the reason I have you break that into binary is because I need to know how many bits it takes to get the number 30 because that will tell us how many bits we need to carve out of our subnet mask or save, save the host in order to get an accurate answer.

00:12:44

Now the great exception is kind of related to this whole process and how binary works. Because binary begins counting from zero these networks values may throw off your calculations for the number of networks and these values may throw off your calculations for the number of hosts. Let me take one of them. Take, let's say

00:13:07

you've been given 200 here let me just clear a little room down here. You've been given the IP address two hundred 200.0.1.0. And the question says, well break that into let's do 16. Break that in to 16 networks. Well when you figure that out in binary we would say

00:13:32

ok there's no one twenty eights, no sixty fours, no thirty Oh, one 16 and everything else is zero so we'd say, okay in that case it would take five bits to get 16 networks. But we can actually get it with four. Four bits are what's only required to get 16 networks and the reason that exception pops in there is because we started counting from zero. Meaning,

00:13:59

what's the biggest number you can get with 15 or oops, gave you the answer there. What's the biggest number you can get with four bits? Well, if we count them up, let me just write the binary values above. 128, 64, 32, 16 8, 4, 2 and 1. The biggest number that we can get if we added up 8 4 2 and 1 that would be 12, 14, 15 right? But, remember when we start counting in binary we start with zero through 15. So technically we can get 16 values or 16 numbers with four bits. Zero through 15 and that's why any time you land on one of these significant binary boundaries, like somebody says well give me 64 networks and you put a one right there. Well, you can actually get 64 with six bits rather than the seven like it looks like it it requires. The same

00:14:53

thing happens in the host values. The following a host values might throw off your calculations. Because let's say they said we want networks of seven hosts per networks. Well, you figure that out and you go okay, no one twenty eights, no sixty fours, thirty twos, sixteen eight, oh, four that leaves us with three, so two, one. That is seven in binary. Well

00:15:18

when we're working with hosts it says well we need you know three different value, you know, three bits to get the number seven because zero this, hang on. Now now I'm messing with my own head. This is one two and four right there so if we add them all up that would be zero through seven if you will. Because that's a seven

00:15:39

of total. So it says well eight is the maximum number that you can get with three bits. Sorry, I don't know if that makes sense at all but meaning when you have three bits the biggest number you can get is eight hosts. Now here's the trouble with the hosts. Any time we're figuring out these

00:15:58

these calculations we always have to subtract two because one of those hosts will be the broadcast. One of them will be the network. So when we're looking at this it shows zero through seven well that gives us eight total values that we can have but if we subtract two from eight were left with six. So while we wanted

00:16:16

seven hosts, that was our requirement give me seven hosts, this would only give you six total values once you subtracted the two. We've come up one short. So I don't need to get into all the technicalities of why this is the way it is. To play it safe this is this is

00:16:33

the rule always subtract one when finding the number of networks. Meaning, if the problem or scenario that you're trying to solve says I want you to figure out a 128 networks networks well subtract one and figure it out for a hundred twenty seven. Or if it's saying you know I want you to figure out thirty

00:16:51

networks subtract one and figure out for 29. It will never hurt you to do this on whatever calculation you're trying to figure out. It will only help you because it will avoid all of these specialized scenarios. Chances are very slim that somebody's going to come up and say, hey I want you to figure out how, you know, give me a network range for 63 hosts per network. I mean, that's pretty weird that somebody would be looking for that value. But nonetheless

00:17:18

we can use this rule always subtract one when finding the number of networks and to play it safe with the host always add one when finding the number of hosts. So if they ask for 63 hosts, you know because of this rule you're going to come up one short so just add one to the number. Say well, I'll figure it out for

00:17:35

64. Someone says I one 20 hosts, add one and figure out for 21. It's going to end up with the same answer if it's not hitting this rule or if it's this rule it may save you a miscalculation. So this is the great exception and I fully describe this and document it in that document that I just showed you. Probably a little little more concise than the way

00:17:55

I've explained it because it's hard when you're trying to show the binary and how that works but that's the only time the three steps will lead you in a little different direction is if one of these values are chosen for the networks or one of these values are chosen for the hosts. With that I will close the

00:18:13

door on IP subnetting. That is the subnetting and the skill that you will need when you're working with anything in the CISCO world because as a CISCO technician you have become the network designer. Sure just about every other certification Microsoft Novell, they all talk about subnetting but you can kind of skate your way through without really knowing what subnetting is about because you don't usually deal with it in the Microsoft and Novell world. You usually are getting your IP addresses from the CISCO designer

00:18:45

that figures out all the networks and divides them up on a map and so on so it's not as critical to those technologies. In CISCO you are the network architect so you have to know how to figure out the subnets and reverse engineer them. So to hit the high points,

00:19:01

three styles: networks, hosts and reverse engineering. I would make sure that you are able to figure those out within a decent amount of time if you're planning on taking the certification exam. And the key to these subnetting systems are practice. I know,

00:19:20

it's brutal, but that is the only way that this will get down in your own mind so if you want you can come up with many different scenarios for your own practice or go on google and type in subnetting. Be warned though, you will see 5,000 different methods of subnetting and once you try and start mixing many of those methods into your mind it can just get confusing. So just look on on-line for examples

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Jeremy Cioara
Nugget trainer since 2003