WEBVTT 0:00:08.060000 --> 0:00:13.480000 All right. Hello and welcome to this INE CCNA boot camp. 0:00:13.480000 --> 0:00:16.840000 This is for the CCNA 200-301. 0:00:16.840000 --> 0:00:19.800000 Welcome to this course and I'm glad to have you with us. 0:00:19.800000 --> 0:00:24.100000 Brett, thank you for joining us here this week. 0:00:24.100000 --> 0:00:26.880000 And just some basic course logistics. 0:00:26.880000 --> 0:00:31.260000 So this is a live course, but it is being recorded for our platform. 0:00:31.260000 --> 0:00:33.480000 So it is running from 9 a.m. 0:00:33.480000 --> 0:00:37.640000 until basically whenever we stop every single day, Eastern time, a five 0:00:37.640000 --> 0:00:41.260000 -day course. So that's our start end times breaks. 0:00:41.260000 --> 0:00:44.100000 We will have breaks peppered throughout the course. 0:00:44.100000 --> 0:00:46.360000 Also going to have a one-hour lunch break that will take every single 0:00:46.360000 --> 0:00:49.460000 day. But for those of you who are watching this as a recorded video, that 0:00:49.460000 --> 0:00:50.700000 doesn't apply to you. 0:00:50.700000 --> 0:00:53.800000 Please ask questions. 0:00:53.800000 --> 0:00:55.620000 Otherwise, the instructor will assume you know something. 0:00:55.620000 --> 0:00:57.540000 So let me pause here on this. 0:00:57.540000 --> 0:01:01.000000 This actually does apply to both the people watching this in the future 0:01:01.000000 --> 0:01:04.460000 as a video as well as Brett as you as the live learner. 0:01:04.460000 --> 0:01:10.820000 So I frequently say this in all of my boot camps, which is that the objective 0:01:10.820000 --> 0:01:16.600000 of any INE boot camp, whether it be CCNA, CCNP all the way up to CCIE, 0:01:16.600000 --> 0:01:22.500000 is that these are really meant as like the capstone to your learning process. 0:01:22.500000 --> 0:01:27.780000 So ideally, you know, you would have spent several months already reading, 0:01:27.780000 --> 0:01:32.620000 watching videos, doing flashcards, taking practice tests, and attending 0:01:32.620000 --> 0:01:36.260000 an INE boot camp would be pretty much the last thing you would do. 0:01:36.260000 --> 0:01:42.200000 Maybe, oh, three or four weeks before you actually have your exam scheduled 0:01:42.200000 --> 0:01:46.060000 to take. And then during the boot camp, you know, hopefully if all went 0:01:46.060000 --> 0:01:49.300000 well, you'd be like walking out of the boot camp saying, okay, well, I 0:01:49.300000 --> 0:01:50.980000 pretty much knew 80% of that. 0:01:50.980000 --> 0:01:54.900000 So that's good. But there was about 20% in there that I struggled with. 0:01:54.900000 --> 0:01:56.280000 I may have gotten lost on. 0:01:56.280000 --> 0:02:00.060000 Now I got three or four weeks before my test to really just fine tune 0:02:00.060000 --> 0:02:02.000000 my studying for that. 0:02:02.000000 --> 0:02:06.780000 So to that end, this boot camp does assume that you've already gone through 0:02:06.780000 --> 0:02:11.680000 all the videos in the CCNA 200-301 learning path. 0:02:11.680000 --> 0:02:13.640000 And this is the last thing you're watching. 0:02:13.640000 --> 0:02:18.720000 So to that end, I'm going to be covering a lot of material here, but not 0:02:18.720000 --> 0:02:23.720000 necessarily at the same depth that I covered in my individual videos. 0:02:23.720000 --> 0:02:28.860000 Okay. So by the time you get to this course, you've already gotten the 0:02:28.860000 --> 0:02:30.360000 meat. You've already gotten the depth of this. 0:02:30.360000 --> 0:02:31.700000 And this is just like a review. 0:02:31.700000 --> 0:02:36.220000 So we're going to be covering a lot of stuff really, really quickly. 0:02:36.220000 --> 0:02:40.520000 And hopefully any questions that you do have, you can just refer to a 0:02:40.520000 --> 0:02:43.900000 previous video where all the nitty gritty, gory details are contained 0:02:43.900000 --> 0:02:45.900000 within that video. 0:02:45.900000 --> 0:02:50.220000 Now for the live learning here for Brett, I absolutely encourage you to 0:02:50.220000 --> 0:02:53.060000 ask questions as we go along the way, which I think will make for a more 0:02:53.060000 --> 0:02:57.360000 interactive, recorded experience for people watching the videos as well. 0:02:57.360000 --> 0:03:01.580000 But just be aware that this is going to be a lot of material over five 0:03:01.580000 --> 0:03:04.200000 days really, really quickly. 0:03:04.200000 --> 0:03:08.120000 And that also sort of influences the labs as well, the lab tasks. 0:03:08.120000 --> 0:03:12.200000 So in some of the previous labs I developed for previous boot camps I 0:03:12.200000 --> 0:03:16.560000 used to have, the labs were more delineated in their instructions. 0:03:16.560000 --> 0:03:18.640000 The instructions were very clear. 0:03:18.640000 --> 0:03:21.460000 There was a lot of screenshots about what you could see. 0:03:21.460000 --> 0:03:24.500000 A lot of times I even said this is the command you should type. 0:03:24.500000 --> 0:03:29.060000 Because this is the capstone to your learning process, I've taken the 0:03:29.060000 --> 0:03:32.200000 approach when designing these labs that, you know, you've already done 0:03:32.200000 --> 0:03:33.660000 this stuff before. 0:03:33.660000 --> 0:03:37.600000 You've already practiced OSPF when you were watching the OSPF video. 0:03:37.600000 --> 0:03:41.380000 You've already practiced network address translation when you were watching 0:03:41.380000 --> 0:03:44.080000 the network address translation videos. 0:03:44.080000 --> 0:03:48.040000 And so, and when you were practicing it there is when you really got introduced 0:03:48.040000 --> 0:03:51.840000 to the commands, the show commands, the debugging commands, the config 0:03:51.840000 --> 0:03:56.120000 commands. So these labs are more high level to where you're going to see 0:03:56.120000 --> 0:04:00.020000 like one or two or three slides of objective bullet points. 0:04:00.020000 --> 0:04:01.180000 Make this happen. 0:04:01.180000 --> 0:04:01.900000 Make this happen. 0:04:01.900000 --> 0:04:06.340000 Make this guy talk to this guy like this. 0:04:06.340000 --> 0:04:07.660000 But it's going to leave it. 0:04:07.660000 --> 0:04:09.360000 It's going to not tell you how. 0:04:09.360000 --> 0:04:11.900000 It's not going to give you the commands or the structure. 0:04:11.900000 --> 0:04:15.060000 So the labs that go along with this boot camp are more of a like a challenge 0:04:15.060000 --> 0:04:19.760000 lab type. So just be aware of that when going into that. 0:04:19.760000 --> 0:04:24.240000 All right. And also as we record this here, interact interactivity is 0:04:24.240000 --> 0:04:28.160000 crucial. So Brett, please ask me questions as we go along. 0:04:28.160000 --> 0:04:30.020000 Should you have any? 0:04:30.020000 --> 0:04:32.100000 All right. So our agenda. 0:04:32.100000 --> 0:04:34.000000 A lot of stuff to cover here. 0:04:34.000000 --> 0:04:35.940000 You guys can read this. 0:04:35.940000 --> 0:04:40.900000 That there's so much more than these seven or eight bullet points here. 0:04:40.900000 --> 0:04:42.520000 These just some high level stuff. 0:04:42.520000 --> 0:04:45.060000 But there's a lot more that goes beyond this. 0:04:45.060000 --> 0:04:49.460000 So if you're familiar with the older CCNA, you'll know some things are 0:04:49.460000 --> 0:04:51.760000 new on here that you may not have had a chance to study. 0:04:51.760000 --> 0:04:53.680000 For example, wireless networking. 0:04:53.680000 --> 0:04:56.040000 Wireless was not a part of the CCU audience switching. 0:04:56.040000 --> 0:05:00.960000 Now it's a pretty big part of the CCNA 200-301. 0:05:00.960000 --> 0:05:04.180000 Also network programmability and software defined networks. 0:05:04.180000 --> 0:05:09.840000 Now at the CCNA level, they don't expect you to do any of that stuff. 0:05:09.840000 --> 0:05:13.960000 So they don't expect you to know how to configure puppet or Ansible or 0:05:13.960000 --> 0:05:17.360000 chef. They don't even really know expect you to know how to go into Cisco 0:05:17.360000 --> 0:05:19.740000 DNA center and navigate the GUI. 0:05:19.740000 --> 0:05:23.720000 It's more of a conceptual thing like you need to know what these things 0:05:23.720000 --> 0:05:27.740000 are. What problem they were trying to solve. 0:05:27.740000 --> 0:05:31.500000 And at a real high level, some of their differences among each other. 0:05:31.500000 --> 0:05:33.620000 So you can sort of compare and contrast them. 0:05:33.620000 --> 0:05:35.440000 That's about it. 0:05:35.440000 --> 0:05:39.240000 And then we also have a lot of other stuff above and beyond this. 0:05:39.240000 --> 0:05:45.400000 Okay, so that pretty much concludes the introduction to the SPOOCamp. 0:05:45.400000 --> 0:05:47.980000 And so now let's go ahead and go into our first topic. 0:05:47.980000 --> 0:05:51.260000 All right, in this video, we're going to be going over an overview of 0:05:51.260000 --> 0:05:54.660000 IPB4, UDP and TCP. 0:05:54.660000 --> 0:05:57.380000 Just sort of reviewing some of these concepts that hopefully you've already 0:05:57.380000 --> 0:05:58.700000 learned previously. 0:05:58.700000 --> 0:06:01.780000 So let's start with the Internet Protocol. 0:06:01.780000 --> 0:06:09.700000 So we know that the main objective of the Internet Protocol is to allow 0:06:09.700000 --> 0:06:14.020000 a device. And in this day and age of the Internet of things, that device 0:06:14.020000 --> 0:06:14.660000 could be a laptop. 0:06:14.660000 --> 0:06:16.600000 It could be a ring doorbell. 0:06:16.600000 --> 0:06:20.180000 It could be an Internet sensor on a refrigerator. 0:06:20.180000 --> 0:06:24.400000 It could be anything that needs connectivity to a network. 0:06:24.400000 --> 0:06:29.040000 So the IP protocol says, I'm going to give you connectivity to the network. 0:06:29.040000 --> 0:06:30.360000 And here's how I'm going to do it. 0:06:30.360000 --> 0:06:33.700000 Number one, I'm going to give you a distinctive address. 0:06:33.700000 --> 0:06:37.500000 And based on this address I give you, you're going to know two things. 0:06:37.500000 --> 0:06:39.700000 You're going to know what network you're on. 0:06:39.700000 --> 0:06:42.800000 And you're going to know what your unique credentials are or your unique 0:06:42.800000 --> 0:06:45.320000 host ideas on that network. 0:06:45.320000 --> 0:06:48.820000 So you can differentiate yourself from other devices on the same network 0:06:48.820000 --> 0:06:52.660000 as you. Next thing I'm going to do is I'm going to give you an address 0:06:52.660000 --> 0:06:56.400000 of another device on the same network as you called a router or what we 0:06:56.400000 --> 0:07:00.360000 would call a default gateway, which now means if you need to send information 0:07:00.360000 --> 0:07:05.380000 to a destination that's not on your network, send it to that guy. 0:07:05.380000 --> 0:07:08.660000 Send it to that default gateway and he'll know how to get it to its ultimate 0:07:08.660000 --> 0:07:13.980000 destination. And then IP also says, okay, we need to make sure that everybody's 0:07:13.980000 --> 0:07:17.340000 putting their information on this network in the same way. 0:07:17.340000 --> 0:07:21.060000 We can't just let people willy-nilly decide what the format of their bits 0:07:21.060000 --> 0:07:22.220000 are going to be. 0:07:22.220000 --> 0:07:27.400000 So IP defines a structure as far as how we need to put stuff on the network. 0:07:27.400000 --> 0:07:30.300000 The structure of various different fields, what the means of those fields 0:07:30.300000 --> 0:07:32.760000 are, how big those fields should be. 0:07:32.760000 --> 0:07:38.340000 So IP gives us that framework so we can take our data, wrap it in this 0:07:38.340000 --> 0:07:41.200000 thing called an IP header, which is a bunch of fields. 0:07:41.200000 --> 0:07:44.960000 Some of those fields are what's the source address, what's my address, 0:07:44.960000 --> 0:07:47.720000 what's the destination I'm going to, as well as some other things, so 0:07:47.720000 --> 0:07:52.180000 that ultimately we can use it to get our data across the network to the 0:07:52.180000 --> 0:07:53.360000 remote destination. 0:07:53.360000 --> 0:07:56.100000 Whether that destination be a server to sitting literally two feet away 0:07:56.100000 --> 0:07:59.980000 from me or another server that's 10 ,000 miles away from me on the other 0:07:59.980000 --> 0:08:02.260000 side of the globe. 0:08:02.260000 --> 0:08:05.240000 So IP is at the networking layer. 0:08:05.240000 --> 0:08:08.160000 So of the OSI model, it's layer three of the OSI model. 0:08:08.160000 --> 0:08:09.760000 It is connectionless. 0:08:09.760000 --> 0:08:14.720000 So if you look in the IP protocol itself, it does not say things like, 0:08:14.720000 --> 0:08:19.360000 hey, here's how you prove that the destination is actually alive. 0:08:19.360000 --> 0:08:23.500000 Here's how you prove that the destination actually got what you're sending 0:08:23.500000 --> 0:08:25.960000 to it. IP doesn't care about such things. 0:08:25.960000 --> 0:08:29.340000 IP just says, hey, let me give you a structure to wrap your information 0:08:29.340000 --> 0:08:33.040000 around. Let me tell you what an address looks like and how your address 0:08:33.040000 --> 0:08:37.560000 should be. So you take your data, wrap it in the structure, send it out, 0:08:37.560000 --> 0:08:40.640000 and just hope it got to its destination. 0:08:40.640000 --> 0:08:44.540000 Now, if an application that you're using, whether that application be 0:08:44.540000 --> 0:08:50.280000 your web browser or your email or whatever, if that application is interested 0:08:50.280000 --> 0:08:53.560000 in knowing, hey, is the destination actually alive? 0:08:53.560000 --> 0:08:55.940000 Did the destination actually get my data? 0:08:55.940000 --> 0:09:00.680000 Well, then it can't use IP to answer those questions, but it can use other 0:09:00.680000 --> 0:09:05.100000 protocols that work hand in hand with IP to answer that. 0:09:05.100000 --> 0:09:07.340000 So let's just take a look and see what IP does. 0:09:07.340000 --> 0:09:11.360000 So number one, so what we're looking at now is, you know, imagine your 0:09:11.360000 --> 0:09:20.220000 data. So let's just focus on a laptop for a moment. 0:09:20.220000 --> 0:09:22.500000 So that's my block of data. 0:09:22.500000 --> 0:09:25.540000 And it's gone down through the OSI protocol layer and now it's hitting 0:09:25.540000 --> 0:09:27.540000 layer three, the networking layer. 0:09:27.540000 --> 0:09:31.160000 And IP says, okay, I got to take this thing and put some additional fields 0:09:31.160000 --> 0:09:35.760000 onto it so it's structured appropriately so I can set it on the network. 0:09:35.760000 --> 0:09:38.620000 So IP says, here's the various fields I'm going to add. 0:09:38.620000 --> 0:09:41.940000 So number one, it says, and actually probably what we should do is start 0:09:41.940000 --> 0:09:49.140000 from bottom up. All right, so, so let's just say that here's, here's a, 0:09:49.140000 --> 0:09:50.220000 here's my payload, right? 0:09:50.220000 --> 0:09:51.900000 So this is the data right there. 0:09:51.900000 --> 0:09:54.400000 Probably shouldn't use green says as blending in. 0:09:54.400000 --> 0:09:57.120000 And IP says, all right, here's I'm going to add to that data. 0:09:57.120000 --> 0:10:02.540000 So number one, right in front of the data, I'm going to add an IP options 0:10:02.540000 --> 0:10:04.620000 field. Probably not. 0:10:04.620000 --> 0:10:08.540000 And notice the IP options field says, if any, IP options in the world 0:10:08.540000 --> 0:10:11.440000 of IPV4 is truly optional. 0:10:11.440000 --> 0:10:17.200000 So matter of fact, IPV4 99% of the time does not use IP options. 0:10:17.200000 --> 0:10:20.340000 So most of the time you won't see any IP options, so it's just going to 0:10:20.340000 --> 0:10:21.900000 scratch that out there. 0:10:21.900000 --> 0:10:23.300000 Probably not going to see that. 0:10:23.300000 --> 0:10:26.620000 So most likely what you're going to see sitting right in front of your 0:10:26.620000 --> 0:10:28.660000 data. So imagine this is here. 0:10:28.660000 --> 0:10:32.500000 Let's say those ones and zeros represent my data. 0:10:32.500000 --> 0:10:36.340000 So what you're going to see right in front of it is your destination IP 0:10:36.340000 --> 0:10:39.080000 address. You know, where's this data going to? 0:10:39.080000 --> 0:10:42.000000 And that is 32 bits long. 0:10:42.000000 --> 0:10:47.080000 So the designers of IP decided that an IP address should be 32 bits. 0:10:47.080000 --> 0:10:50.380000 After that, you're going to see your source address, which is the address 0:10:50.380000 --> 0:10:53.080000 of your laptop where it came from. 0:10:53.080000 --> 0:10:57.020000 Okay. And then we're going to sort of wrap around this way right here. 0:10:57.020000 --> 0:10:59.980000 Okay. Then we're going to see a header checksum. 0:10:59.980000 --> 0:11:05.040000 And basically what that is is we take all the bits of this header every 0:11:05.040000 --> 0:11:09.680000 single bit, run it through a formula called a hashing or a hash digest 0:11:09.680000 --> 0:11:13.020000 formula. And that formula creates what's called a hash. 0:11:13.020000 --> 0:11:16.640000 Now, if you're not familiar with hash hashes or digest, basically what 0:11:16.640000 --> 0:11:22.400000 they do is they say, look, you can give me information of any size. 0:11:22.400000 --> 0:11:24.580000 So a hash says, Hey, give me two bits. 0:11:24.580000 --> 0:11:25.720000 Give me 20 bits. 0:11:25.720000 --> 0:11:27.260000 Give me 2000 bits. 0:11:27.260000 --> 0:11:28.700000 It doesn't matter. 0:11:28.700000 --> 0:11:30.220000 Give me a bunch of bits. 0:11:30.220000 --> 0:11:35.240000 I will plug it in my formula and I will give back to you a hash digest. 0:11:35.240000 --> 0:11:36.680000 Now, what is a hash digest? 0:11:36.680000 --> 0:11:40.140000 Well, a hash digest says, look, regardless of the size of what you're 0:11:40.140000 --> 0:11:43.060000 going to see, if you gave to me, I'm going to give you a number back. 0:11:43.060000 --> 0:11:44.820000 It's always a fixed size. 0:11:44.820000 --> 0:11:47.900000 Like, for example, some hashing formulas say, I'm going to give you back 0:11:47.900000 --> 0:11:52.720000 128 bit number. So even if you fed into my formula, just a four bit number 0:11:52.720000 --> 0:11:58.140000 or a 4000 bit number, I'm going to work my magic and give you back a 128 0:11:58.140000 --> 0:12:00.720000 bit number. Now, what's the purpose of that? 0:12:00.720000 --> 0:12:05.240000 Well, the purpose of that is, if I, let's say I gave it a 2000 bit number. 0:12:05.240000 --> 0:12:08.000000 All right, let's say that all the bits in these fields were 2000 bits 0:12:08.000000 --> 0:12:13.920000 in total. So if I took those 2000 bits and I ran it through my hash and 0:12:13.920000 --> 0:12:17.980000 it came up with 128 bit number, let's just say it's a 1234. 0:12:17.980000 --> 0:12:22.380000 If I took those exact same 2000 bits and I ran through the formula again, 0:12:22.380000 --> 0:12:26.200000 I would get the exact same number, a 1234. 0:12:26.200000 --> 0:12:27.960000 So what's the purpose of this field then? 0:12:27.960000 --> 0:12:32.360000 The purpose is, once I give you, let's say you're the destination, I give 0:12:32.360000 --> 0:12:36.940000 you my IP packet, you're going to take the exact same bits, run them through 0:12:36.940000 --> 0:12:40.280000 the exact same formula, and you're going to compare the digest you come 0:12:40.280000 --> 0:12:44.760000 up with with the digest that I stuck in here in the header checksum. 0:12:44.760000 --> 0:12:49.460000 If those two numbers are the same, you will know, oh, this IP header is 0:12:49.460000 --> 0:12:51.040000 valid. Nothing's been corrupted. 0:12:51.040000 --> 0:12:53.180000 Nothing's been changed in transit. 0:12:53.180000 --> 0:12:57.820000 I can trust it. But if you take all the bits of the IP header, you come 0:12:57.820000 --> 0:13:01.680000 up with a digest and it does not match the header checksum. 0:13:01.680000 --> 0:13:03.360000 Now you can't trust this thing. 0:13:03.360000 --> 0:13:06.720000 That means, oh, something's been changed or modified in here. 0:13:06.720000 --> 0:13:08.500000 I can't trust this IP header. 0:13:08.500000 --> 0:13:10.320000 You have to destroy the whole packet. 0:13:10.320000 --> 0:13:13.060000 So it's a way of detecting errors. 0:13:13.060000 --> 0:13:16.580000 Now, the header checksum cannot tell you what has been changed. 0:13:16.580000 --> 0:13:18.920000 So there's no way to fix what's been changed. 0:13:18.920000 --> 0:13:22.120000 All it can do is provide sort of like a trustworthy factor. 0:13:22.120000 --> 0:13:25.780000 Is this IP header trustworthy or is it not trustworthy? 0:13:25.780000 --> 0:13:27.680000 That's what the checksum is. 0:13:27.680000 --> 0:13:30.980000 Then in front of that, we're going to have the protocol. 0:13:30.980000 --> 0:13:34.760000 So that's basically a field that's going to have a defined number in it 0:13:34.760000 --> 0:13:36.900000 that says what comes next. 0:13:36.900000 --> 0:13:40.980000 Because after all, after the IP header here, in reality, it's probably 0:13:40.980000 --> 0:13:44.140000 not your email. There's probably something in front of that, like a TCP 0:13:44.140000 --> 0:13:48.080000 header or a UDP header or maybe some routing header or something. 0:13:48.080000 --> 0:13:54.200000 So the protocol will contain a number like 6 for TCP, 17 for UDP. 0:13:54.200000 --> 0:13:58.980000 They'll tell you the processor that's receiving this what is behind the 0:13:58.980000 --> 0:14:04.560000 IP header. Then we have the time to live, which is a number. 0:14:04.560000 --> 0:14:06.680000 It's going to start out as a non-zero number. 0:14:06.680000 --> 0:14:09.700000 Most applications will give a time to live of 255. 0:14:09.700000 --> 0:14:11.900000 That's the maximum that can fit in here. 0:14:11.900000 --> 0:14:14.380000 Because only an 8-bit field. 0:14:14.380000 --> 0:14:19.380000 And as this packet, and that's what we call this, right, data with an 0:14:19.380000 --> 0:14:22.440000 IP header, we call that whole thing a packet. 0:14:22.440000 --> 0:14:25.800000 As this packet goes from one router to the next router to the next router 0:14:25.800000 --> 0:14:29.880000 on its way to the destination, every router has to decrement the time 0:14:29.880000 --> 0:14:33.340000 to live field. So it starts out with some non-zero number. 0:14:33.340000 --> 0:14:38.820000 Now, you can get a packet all the way around the globe in less than 255 0:14:38.820000 --> 0:14:42.780000 hops. So a packet should never expire. 0:14:42.780000 --> 0:14:45.060000 But let's say something weird happened. 0:14:45.060000 --> 0:14:48.740000 And this packet went through like 255 routers. 0:14:48.740000 --> 0:14:52.280000 Okay, so it's gone from 255 to 254, 253, 252. 0:14:52.280000 --> 0:14:54.600000 Now it's gone all the way way out there. 0:14:54.600000 --> 0:14:58.440000 And some router way out there, like router number 255 gets this packet. 0:14:58.440000 --> 0:15:02.580000 Here comes a packet coming in and it has a time to live of one on it. 0:15:02.580000 --> 0:15:05.000000 So the router says, oh, time to live of one. 0:15:05.000000 --> 0:15:06.700000 I need to decrement it to zero. 0:15:06.700000 --> 0:15:10.720000 Guess what? When the time to live reach a zero, that means it's time to 0:15:10.720000 --> 0:15:12.820000 live has expired. 0:15:12.820000 --> 0:15:15.160000 You cannot be alive anymore packet. 0:15:15.160000 --> 0:15:18.580000 And so that packet has to be thrown away by the router. 0:15:18.580000 --> 0:15:22.200000 So the main idea behind the time to live is it's really there as a loop 0:15:22.200000 --> 0:15:25.060000 prevention mechanism to prevent a packet. 0:15:25.060000 --> 0:15:28.240000 If a packet got stuck in a routing loop and just circled and circled and 0:15:28.240000 --> 0:15:33.560000 circled forever, this would be a way of stopping it from circling forever. 0:15:33.560000 --> 0:15:37.760000 Eventually the time to live would decrement to zero packets lifetime is 0:15:37.760000 --> 0:15:39.520000 over. Throw it away. 0:15:39.520000 --> 0:15:41.120000 All right, time to live. 0:15:41.120000 --> 0:15:44.920000 And then we have three more fields here. 0:15:44.920000 --> 0:15:51.100000 So I'll just put these right there, the fragmentation, the fragment offset, 0:15:51.100000 --> 0:15:53.880000 the flags and the identification. 0:15:53.880000 --> 0:15:56.980000 And that is used for fragmentation. 0:15:56.980000 --> 0:16:00.160000 So the idea here, and once I'm not going to get into the the gory details 0:16:00.160000 --> 0:16:04.240000 of this, but the idea being that if a packet needs to be fragmented for 0:16:04.240000 --> 0:16:08.440000 router receives a packet and the router says, oh, I can't transmit this 0:16:08.440000 --> 0:16:11.600000 out my outbound interface because it's too big. 0:16:11.600000 --> 0:16:12.620000 I need to fragment. 0:16:12.620000 --> 0:16:14.760000 I need to cut it up in a smaller pieces. 0:16:14.760000 --> 0:16:17.920000 Well, now the router says, okay, if I'm going to do that, I need to make 0:16:17.920000 --> 0:16:19.460000 sure that the destination. 0:16:19.460000 --> 0:16:23.860000 A, when he gets these fragments recognizes that, oh, these are not full 0:16:23.860000 --> 0:16:25.700000 self contained packets. 0:16:25.700000 --> 0:16:26.800000 These are fragments. 0:16:26.800000 --> 0:16:27.660000 I've just gotten. 0:16:27.660000 --> 0:16:32.280000 And B, it needs to know these are all fragments of one cohesive packet, 0:16:32.280000 --> 0:16:37.180000 right? And then see how do I put the fragments back together in the appropriate 0:16:37.180000 --> 0:16:41.780000 order so I can reconstruct the original packet as it looked. 0:16:41.780000 --> 0:16:44.180000 And that's what the purpose of these fields are for. 0:16:44.180000 --> 0:16:45.500000 So just real quickly here. 0:16:45.500000 --> 0:16:48.120000 I'm going to delete this. 0:16:48.120000 --> 0:16:52.480000 So the idea is that, get rid of some of this stuff here. 0:16:52.480000 --> 0:16:59.480000 All right, so the idea here is that number one, every packet that's ever 0:16:59.480000 --> 0:17:03.060000 generated has a unique number called an identification number, just a 0:17:03.060000 --> 0:17:05.760000 random number. You can't predict what it is. 0:17:05.760000 --> 0:17:09.560000 Okay, so if a router is going to take a packet and cut it up into multiple 0:17:09.560000 --> 0:17:12.940000 fragments, every fragment is going to have a new IP header. 0:17:12.940000 --> 0:17:16.680000 It's going to look like a new IP packet, even though it's a smaller fragment 0:17:16.680000 --> 0:17:18.200000 of a bigger packet. 0:17:18.200000 --> 0:17:21.860000 Well, all those fragments will have the identification number of the original 0:17:21.860000 --> 0:17:25.660000 packet. So whatever the original packet was before it was divided, that 0:17:25.660000 --> 0:17:29.320000 ID will be copied into the fragments. 0:17:29.320000 --> 0:17:31.580000 All right, so they'll all have the same identification number in their 0:17:31.580000 --> 0:17:37.200000 header. Number two, the flags field indicates to the receiver whether 0:17:37.200000 --> 0:17:40.840000 there are more fragments to come or if this is the last fragment. 0:17:40.840000 --> 0:17:44.700000 Okay, so the very first fragment, the second fragment, the third fragment, 0:17:44.700000 --> 0:17:48.560000 they'll all have a bit set here in the flags field called the more fragments 0:17:48.560000 --> 0:17:53.460000 bit. The very last fragment, that bit will be turned off. 0:17:53.460000 --> 0:17:56.380000 That's how you know, that's the very last one. 0:17:56.380000 --> 0:18:00.700000 And then lastly, the fragment offset says, okay, in the scheme of things, 0:18:00.700000 --> 0:18:02.240000 where's this fragment sit? 0:18:02.240000 --> 0:18:05.140000 Is this fragment like the third one, the fifth one, the second one, the 0:18:05.140000 --> 0:18:08.160000 first one? How do we reconstruct the original packet? 0:18:08.160000 --> 0:18:09.620000 Where's this fragment go? 0:18:09.620000 --> 0:18:12.980000 Fragment offset gives us that information. 0:18:12.980000 --> 0:18:17.980000 So I'll just put right here, frag, to cover all three of those fields. 0:18:17.980000 --> 0:18:21.700000 And then we have the total length, which is the length of the IP header 0:18:21.700000 --> 0:18:24.660000 plus the data behind it. 0:18:24.660000 --> 0:18:27.600000 So we're running out of room here, so I'm going to wrap around. 0:18:27.600000 --> 0:18:31.840000 And then we have the type of service bit or type of service byte. 0:18:31.840000 --> 0:18:33.720000 That's eight bits. 0:18:33.720000 --> 0:18:37.400000 And that's typically used to identify the priority of a packet. 0:18:37.400000 --> 0:18:39.840000 So you may have heard of something called quality of service, and we're 0:18:39.840000 --> 0:18:42.320000 going to cover QS a little bit in this bootcamp as well, because that's 0:18:42.320000 --> 0:18:43.760000 part of the new CCNA. 0:18:43.760000 --> 0:18:48.620000 A quality of service depends on a networking device being able to identify 0:18:48.620000 --> 0:18:51.160000 the priority of a packet. 0:18:51.160000 --> 0:18:55.120000 And typically we look at the setting of the type of service byte to identify 0:18:55.120000 --> 0:18:58.060000 that. And we'll go into much more detail of that when we get into the 0:18:58.060000 --> 0:19:02.300000 QS section. And then we have the IP header length. 0:19:02.300000 --> 0:19:07.820000 IP header length, which basically says, what is the length of this header? 0:19:07.820000 --> 0:19:11.880000 Because remember, the options field may or may not be there. 0:19:11.880000 --> 0:19:16.680000 So the receiver has to know where's the IP header end and the next header 0:19:16.680000 --> 0:19:19.520000 begin. They use the IP header length for that. 0:19:19.520000 --> 0:19:23.300000 And then lastly, it has the version field. 0:19:23.300000 --> 0:19:25.720000 And if we're talking about IP version four, that would have the number 0:19:25.720000 --> 0:19:29.480000 four in it. If we're talking about IP version six, it would have the number 0:19:29.480000 --> 0:19:33.240000 six in it. But IP version six has a different header structure. 0:19:33.240000 --> 0:19:35.680000 It's not quite what this looks like right here. 0:19:35.680000 --> 0:19:39.460000 It does have a version field, but a lot of the other fields have different 0:19:39.460000 --> 0:19:42.600000 meanings and they show up in different places. 0:19:42.600000 --> 0:19:45.860000 We'll talk about that when we get to IPV six. 0:19:45.860000 --> 0:19:50.800000 So that's all the stuff that IP adds to the front of your payload. 0:19:50.800000 --> 0:19:52.540000 So the packet's basically going this way. 0:19:52.540000 --> 0:19:56.700000 So if I was receiving this IP packet coming into me, first thing I would 0:19:56.700000 --> 0:19:58.900000 see is the version field. 0:19:58.900000 --> 0:20:02.960000 As I follow my way back, right, if I'm the IP protocol, I know, okay, 0:20:02.960000 --> 0:20:05.160000 the version field is four bits long. 0:20:05.160000 --> 0:20:08.300000 The next field I should see is the IP header length, which is four bits 0:20:08.300000 --> 0:20:11.420000 long. The next field I should see after that is the type of service, which 0:20:11.420000 --> 0:20:13.200000 is eight bits long. 0:20:13.200000 --> 0:20:18.560000 So the IP protocol knows to expect these fields in this order and it can 0:20:18.560000 --> 0:20:27.760000 read them as they come in. 0:20:27.760000 --> 0:20:28.300000 So I'm going to go ahead and see if I can get to the address. 0:20:28.300000 --> 0:20:31.260000 All right, let's talk a little bit about the addressing scheme that IP 0:20:31.260000 --> 0:20:35.120000 uses. So I mentioned just a moment ago that the address IP comes up with. 0:20:35.120000 --> 0:20:39.220000 Now this is IP version four is a 32 bit address. 0:20:39.220000 --> 0:20:42.560000 All right, so 32 bits of the address. 0:20:42.560000 --> 0:20:45.280000 And the address was defined. 0:20:45.280000 --> 0:20:50.360000 They said, look, let's imagine this box here defines my IP version for 0:20:50.360000 --> 0:20:55.700000 address. And we know the whole thing is 32 bits end to end. 0:20:55.700000 --> 0:21:03.480000 Some of those bits represent the network portion of the ID of the IP address. 0:21:03.480000 --> 0:21:05.720000 Others represent the host portion. 0:21:05.720000 --> 0:21:13.900000 Host address. Okay, so, and this is a very critical part of IP. 0:21:13.900000 --> 0:21:17.600000 You may have heard of the difference between route head protocols and 0:21:17.600000 --> 0:21:18.740000 routing protocols. 0:21:18.740000 --> 0:21:22.200000 You need to know the difference, especially if you're taking some exam, 0:21:22.200000 --> 0:21:24.460000 whether it be a Cisco exam or other exam. 0:21:24.460000 --> 0:21:30.320000 So a route head protocol, a routed protocol is a protocol that a provides 0:21:30.320000 --> 0:21:35.960000 an address. So it gives your system some sort of an address and be that 0:21:35.960000 --> 0:21:41.080000 address is subdividable into a network portion and a host portion. 0:21:41.080000 --> 0:21:44.960000 For example, my laptop also has a MAC address. 0:21:44.960000 --> 0:21:48.600000 That's another address, but that is not a routeable address because there's 0:21:48.600000 --> 0:21:50.360000 no way to divide a MAC address. 0:21:50.360000 --> 0:21:53.540000 No portion of the MAC address represents the network that I'm sitting 0:21:53.540000 --> 0:21:59.060000 on. But a layer three address like IP before, IPB six used to be Apple 0:21:59.060000 --> 0:22:01.460000 talk, used to be IPX. 0:22:01.460000 --> 0:22:04.180000 All those addresses that sit at layer three, what they have in common 0:22:04.180000 --> 0:22:07.740000 is there's some dividing line between some of the bits representing the 0:22:07.740000 --> 0:22:11.840000 network, some of the bits representing the host. 0:22:11.840000 --> 0:22:15.560000 Now, how do we actually represent addresses because clearly, you know, 0:22:15.560000 --> 0:22:18.740000 if you ask me Keith, what's your IPB four address? 0:22:18.740000 --> 0:22:23.160000 If I said, Oh, my IPB four addresses this 101110111, you'd be looking 0:22:23.160000 --> 0:22:25.220000 at me like, what is wrong with you? 0:22:25.220000 --> 0:22:26.740000 You know, go get it on your medication. 0:22:26.740000 --> 0:22:29.060000 That's not how we talk about IPB four. 0:22:29.060000 --> 0:22:33.760000 So in order to make IP addresses more human friendly, what we do is we 0:22:33.760000 --> 0:22:38.060000 take every four bits, which I think would be if I did my counting right, 0:22:38.060000 --> 0:22:40.240000 I think that is four bit. 0:22:40.240000 --> 0:22:41.440000 That's every eight bits. 0:22:41.440000 --> 0:22:44.240000 So one, two, three, four, one, two, oh, not quite. 0:22:44.240000 --> 0:22:45.700000 So there's eight bits right there. 0:22:45.700000 --> 0:22:47.780000 So there's my bite, right? 0:22:47.780000 --> 0:22:50.940000 And whatever that number is, we translate to decimal. 0:22:50.940000 --> 0:22:54.140000 I don't know what, you know, I should, you should know what it is, right? 0:22:54.140000 --> 0:22:56.120000 The 128 bit is turned on. 0:22:56.120000 --> 0:22:57.080000 What else do we have here? 0:22:57.080000 --> 0:23:03.500000 The 32 bit, 16 bit, eight bit, and we got the two bit and the one bit. 0:23:03.500000 --> 0:23:06.200000 So, you know, whatever that adds up to, let's just see if we, I'm not 0:23:06.200000 --> 0:23:06.740000 going to do the math. 0:23:06.740000 --> 0:23:08.180000 You guys can do the math in your head. 0:23:08.180000 --> 0:23:11.500000 So whatever that is, let's just put a fake number on there. 0:23:11.500000 --> 0:23:13.640000 Let's say that was 165. 0:23:13.640000 --> 0:23:15.200000 It probably isn't. 0:23:15.200000 --> 0:23:18.140000 Otherwise I should be, you know, guessing people's weight at the fair 0:23:18.140000 --> 0:23:19.460000 if I'm able to get that one right. 0:23:19.460000 --> 0:23:21.140000 But let's say it's 165. 0:23:21.140000 --> 0:23:23.900000 So we take our first bite in binary. 0:23:23.900000 --> 0:23:25.740000 We translate it to a decimal number. 0:23:25.740000 --> 0:23:28.540000 We put a dot and then we rinse and repeat. 0:23:28.540000 --> 0:23:32.040000 So an IP before address when we take all 32 bits. 0:23:32.040000 --> 0:23:35.780000 Ends up composed of four octets. 0:23:35.780000 --> 0:23:38.860000 And we represent those as dotted decimal. 0:23:38.860000 --> 0:23:42.060000 So this is the typical way you see, not like that. 0:23:42.060000 --> 0:23:48.560000 This is the typical way you represent an IP address 120 dot 17 dot 3 dot 0:23:48.560000 --> 0:23:54.320000 199. Each one of these things is a decimal number that represents eight 0:23:54.320000 --> 0:24:02.080000 bits of binary. Eight, eight, eight, and eight gives us our total of 32 0:24:02.080000 --> 0:24:07.380000 bits. And some portion of these bits, if we start from the left and we 0:24:07.380000 --> 0:24:12.820000 work our way right, some portion of this represents the network ID. 0:24:12.820000 --> 0:24:15.320000 So for example, that was my laptop. 0:24:15.320000 --> 0:24:20.580000 If my laptop had that IP address and if it knew that 120 dot 17 dot 3 0:24:20.580000 --> 0:24:23.000000 is the network, my laptop would know. 0:24:23.000000 --> 0:24:27.540000 Oh, if I ever need to send an IP packet to somebody else. 0:24:27.540000 --> 0:24:33.160000 And their address also begins with 120 dot 17 dot 3. 0:24:33.160000 --> 0:24:36.200000 They must be on the same network as me. 0:24:36.200000 --> 0:24:39.240000 Whereas conversely, if I'm sending a packet some destination that's not 0:24:39.240000 --> 0:24:43.900000 starting with 120 dot 17 dot 3, they are not on the same network as me, 0:24:43.900000 --> 0:24:46.440000 which means I need to use my default gateway. 0:24:46.440000 --> 0:24:50.500000 I need to send my packet to them, which raises the logical question. 0:24:50.500000 --> 0:24:55.520000 How does a device know if I give a device a 32 bit IP address, how does 0:24:55.520000 --> 0:24:57.160000 it know where that dividing line is? 0:24:57.160000 --> 0:24:58.460000 Is it the first number? 0:24:58.460000 --> 0:25:00.700000 Is the network and the rest of it is host? 0:25:00.700000 --> 0:25:03.300000 Is it the first, you know, two octets? 0:25:03.300000 --> 0:25:04.040000 How does it know? 0:25:04.040000 --> 0:25:08.120000 Well, in the world of IP before the way we know that is by using something 0:25:08.120000 --> 0:25:10.420000 called a subnet mask. 0:25:10.420000 --> 0:25:12.540000 So you've probably seen something like this. 0:25:12.540000 --> 0:25:17.900000 So if I say, hey, your address is 120 17 3 dot 165. 0:25:17.900000 --> 0:25:25.940000 And I say, and your subnet mask is 255 255 0 0. 0:25:25.940000 --> 0:25:31.440000 Well, the subnet mask explicitly tells the device how many of these bits 0:25:31.440000 --> 0:25:32.980000 are the network. 0:25:32.980000 --> 0:25:37.760000 So in this particular case with a subnet mask of 255 255, that means the 0:25:37.760000 --> 0:25:44.320000 first two bytes belong to the network 120 dot 17 belongs to the network. 0:25:44.320000 --> 0:25:48.040000 Now, once again, because this is a CCNA bootcamp, which is meant at the 0:25:48.040000 --> 0:25:51.460000 end of the learning path, by now you should have already gone through. 0:25:51.460000 --> 0:25:57.020000 I have a like a six hour video course on IP before addressing subnetting 0:25:57.020000 --> 0:26:00.880000 and VLSM. These are things that are critical for you. 0:26:00.880000 --> 0:26:06.020000 If you're going to take any CCNA exam or CCIE or CCNP or anything in between. 0:26:06.020000 --> 0:26:09.000000 So we're not going to go into the details of that here, because I'm assuming 0:26:09.000000 --> 0:26:11.780000 you've already spent those six hours before watching this. 0:26:11.780000 --> 0:26:15.040000 And you're already familiar with IP before addressing and subnetting. 0:26:15.040000 --> 0:26:19.480000 So this is just a review here of how a subnet mask is used in conjunction 0:26:19.480000 --> 0:26:20.800000 with an IP address. 0:26:20.800000 --> 0:26:25.420000 I will tell you that if you're weak on this, if if I give you an IP address 0:26:25.420000 --> 0:26:29.660000 in a subnet mask like this, and I say, hey, identify for me what network 0:26:29.660000 --> 0:26:31.280000 this belongs to. 0:26:31.280000 --> 0:26:36.260000 Identify for me the broadcast address that this host would be listening 0:26:36.260000 --> 0:26:38.940000 to. You need to be able to answer those questions. 0:26:38.940000 --> 0:26:43.880000 If you can't do that in a quick format, review IP before addressing and 0:26:43.880000 --> 0:26:53.240000 subting and make sure that you can. 0:26:53.240000 --> 0:26:55.760000 All right, communication types. 0:26:55.760000 --> 0:27:00.080000 So in the layer three in the world of IP before, we have three different 0:27:00.080000 --> 0:27:01.560000 sort of destinations. 0:27:01.560000 --> 0:27:06.240000 I could send my packet to most of the time I'm going to be sending it 0:27:06.240000 --> 0:27:11.220000 as a unicast, which means that packet is going from my laptop to one destination. 0:27:11.220000 --> 0:27:15.400000 That one destination is probably a server, like a web server or an email 0:27:15.400000 --> 0:27:18.860000 server. It could be another client, though, another host, but that's one 0:27:18.860000 --> 0:27:21.000000 to one. That's unicast. 0:27:21.000000 --> 0:27:24.760000 We could do multicast. 0:27:24.760000 --> 0:27:29.740000 So multicast is more often used in video and audio environments. 0:27:29.740000 --> 0:27:36.740000 For example, let's say that our corporate CEO was going to be talking 0:27:36.740000 --> 0:27:40.860000 about some big new bonus structure at three o'clock this afternoon. 0:27:40.860000 --> 0:27:44.720000 And he's going to be doing a video on that, a live streaming video for 0:27:44.720000 --> 0:27:46.440000 the entire company to watch. 0:27:46.440000 --> 0:27:51.180000 Okay. Well, you know, our company might have 500 employees. 0:27:51.180000 --> 0:27:56.140000 It, you know, when we train our camera on him and that camera feeds into 0:27:56.140000 --> 0:27:59.560000 a computer on the back end, which is digitizing all this and turning his 0:27:59.560000 --> 0:28:02.080000 video into IP packets. 0:28:02.080000 --> 0:28:05.320000 It wouldn't make a lot of sense to say, okay, we're going to take his 0:28:05.320000 --> 0:28:08.760000 stream of packets and send it to Joe at 111. 0:28:08.760000 --> 0:28:13.020000 They're going to duplicate it and send to Sally at 1112 and then we're 0:28:13.020000 --> 0:28:17.920000 going to duplicate it 499 more times to send it to everybody. 0:28:17.920000 --> 0:28:23.240000 The CPU, the processing power that would be required to duplicate a video 0:28:23.240000 --> 0:28:27.900000 audio stream dozens or hundreds of times would be immense and doesn't 0:28:27.900000 --> 0:28:29.980000 make a lot of sense to do that. 0:28:29.980000 --> 0:28:32.700000 So we say, okay, let me skip down here. 0:28:32.700000 --> 0:28:35.060000 We could say, well, I'm going to do broadcast then. 0:28:35.060000 --> 0:28:39.060000 So with broadcast, you have a special IP address that everybody knows 0:28:39.060000 --> 0:28:41.120000 means this means everybody. 0:28:41.120000 --> 0:28:47.920000 So when I send a packet to a broadcast IP address, such as this, this 0:28:47.920000 --> 0:28:52.580000 is what's called the general broadcast address. 0:28:52.580000 --> 0:28:57.060000 When I send a packet to that, that means I want everybody to pay attention 0:28:57.060000 --> 0:29:00.800000 to this. Okay, I need everybody to pick this up. 0:29:00.800000 --> 0:29:03.260000 Well, here's the downside to that. 0:29:03.260000 --> 0:29:09.060000 What if several employees in my company aren't interested in this broadcast, 0:29:09.060000 --> 0:29:13.260000 right? You know, of my 500 employees, let's say a hundred of them aren't 0:29:13.260000 --> 0:29:14.640000 even on the bonus schedule. 0:29:14.640000 --> 0:29:18.120000 You know, their pay rate, their job grade doesn't even title them to a 0:29:18.120000 --> 0:29:20.580000 bonus. So they don't care about this video. 0:29:20.580000 --> 0:29:22.060000 They don't need to watch it. 0:29:22.060000 --> 0:29:25.000000 So I don't want to send out a broadcast, which means every device has 0:29:25.000000 --> 0:29:29.520000 to be interrupted with this packet when not every device cares about this 0:29:29.520000 --> 0:29:34.200000 packet. So now I've got 400 people that do want to watch it, 100 people 0:29:34.200000 --> 0:29:35.500000 that could care less. 0:29:35.500000 --> 0:29:39.180000 How do I get this video stream to those 400 individuals who want to see 0:29:39.180000 --> 0:29:42.200000 it? Well, I can't use broadcast because I don't want to bother the 100 0:29:42.200000 --> 0:29:43.460000 over here. They don't care about it. 0:29:43.460000 --> 0:29:48.140000 I don't want to use unicast because I can't send 400 individual streams 0:29:48.140000 --> 0:29:49.080000 to these people. 0:29:49.080000 --> 0:29:51.600000 It's just going to be way too much. 0:29:51.600000 --> 0:29:53.900000 This is where I could use multicast. 0:29:53.900000 --> 0:29:57.380000 So with multicast, you say, okay, well, you might recall when you learned 0:29:57.380000 --> 0:30:01.540000 about IP addressing, that there were ranges of IP addresses. 0:30:01.540000 --> 0:30:04.700000 There was A, B, C, D, and E. 0:30:04.700000 --> 0:30:06.840000 These were classes of addresses. 0:30:06.840000 --> 0:30:10.920000 And class D is what's used for multicast. 0:30:10.920000 --> 0:30:13.640000 Do you remember what a class D address was? 0:30:13.640000 --> 0:30:17.940000 Class D addresses start at 224. 0:30:17.940000 --> 0:30:25.240000 Anything. And then they go up to 239. 0:30:25.240000 --> 0:30:28.660000 That's the class D space. 0:30:28.660000 --> 0:30:31.060000 That is used for multicast. 0:30:31.060000 --> 0:30:32.620000 So here's how it works. 0:30:32.620000 --> 0:30:36.240000 So we decide in advance before our CEO even gets on camera, we set up 0:30:36.240000 --> 0:30:39.260000 our computer that's attached to the camera that's going to be digitizing 0:30:39.260000 --> 0:30:40.480000 him. We set that up. 0:30:40.480000 --> 0:30:44.620000 We say, okay, all the packets are created as a result of his video are 0:30:44.620000 --> 0:30:49.280000 going to go to, let's say, 225.777. 0:30:49.280000 --> 0:30:52.620000 So we're going to pick that address from the class D space. 0:30:52.620000 --> 0:30:56.120000 Now what we do is we have some website that people can go to. 0:30:56.120000 --> 0:30:59.300000 So like our internal employees go to this website and it shows a directory 0:30:59.300000 --> 0:31:03.220000 or a listing of all the multicast sessions that day. 0:31:03.220000 --> 0:31:04.340000 And so we go to that website. 0:31:04.340000 --> 0:31:09.400000 We pre-program it to say, okay, CEO's bonus structure video is going to 0:31:09.400000 --> 0:31:15.060000 be today from 12 to 1230 and the address it's going to is 225.777. 0:31:15.060000 --> 0:31:19.840000 Okay, so if you as an employee want to watch this, you would click on 0:31:19.840000 --> 0:31:23.600000 this directory. You would see the link right there to the video stream. 0:31:23.600000 --> 0:31:27.940000 You would click that and then what's that doing in the background that's 0:31:27.940000 --> 0:31:32.980000 programming your laptop to now not only pay attention to packets coming 0:31:32.980000 --> 0:31:37.880000 to you as a unicast, but you're now also programming your laptop to pick 0:31:37.880000 --> 0:31:41.560000 up packets going to this multicast address. 0:31:41.560000 --> 0:31:44.920000 Right? Those other hundred people that could care less, their laptops 0:31:44.920000 --> 0:31:47.200000 are not listening to 225.777. 0:31:47.200000 --> 0:31:48.840000 They couldn't care about that. 0:31:48.840000 --> 0:31:53.880000 But you and your 399 cohorts who want this video, you have now programmed 0:31:53.880000 --> 0:31:56.160000 your laptop to pay attention to that. 0:31:56.160000 --> 0:32:01.980000 So now the video server can send out just a single stream of packets. 0:32:01.980000 --> 0:32:07.480000 All those packets are going to 225.777 and only the devices that are actually 0:32:07.480000 --> 0:32:11.780000 programmed to listen to that will actually pick up those packets and be 0:32:11.780000 --> 0:32:14.000000 able to watch it. 0:32:14.000000 --> 0:32:18.000000 Now multicast gets a lot more complicated than that at the CCNA level 0:32:18.000000 --> 0:32:21.080000 though. That's all you need to know about multicast and how it works. 0:32:21.080000 --> 0:32:26.300000 Just know that it's a one to many type of scenario and it utilizes addresses 0:32:26.300000 --> 0:32:29.420000 in the class D addressing space. 0:32:29.420000 --> 0:32:33.040000 Once again, this is IPv4 and IPv6. 0:32:33.040000 --> 0:32:36.600000 There is also a concept of multicast, but it uses a completely different 0:32:36.600000 --> 0:32:42.760000 addressing structure for that. 0:32:42.760000 --> 0:32:47.620000 All right, and that concludes this particular video. 0:32:47.620000 --> 0:32:49.240000 Thank you so much for watching.