1 00:00:02,690 --> 00:00:08,528 [music] 2 00:00:08,553 --> 00:00:10,878 So with what we've been doing so far with 3 00:00:10,878 --> 00:00:12,746 subnetting we've been focused pretty much 4 00:00:12,746 --> 00:00:17,384 exclusively on given some base starting network which 5 00:00:17,384 --> 00:00:20,487 you can't touch, you can't modify, and then asking 6 00:00:20,487 --> 00:00:23,257 yourself, okay, how many networks do I actually need 7 00:00:23,257 --> 00:00:27,261 in my organization beyond this one? Oh, I need eight. I 8 00:00:27,261 --> 00:00:31,698 need 15. I need 37. Figuring out, okay, of my available 9 00:00:31,698 --> 00:00:35,168 host bits how many of those do I need to steal? How many 10 00:00:35,168 --> 00:00:38,338 do I need to convert in to subnetting bits so I can 11 00:00:38,338 --> 00:00:41,909 take this one network I originally got and subdivide 12 00:00:41,909 --> 00:00:45,379 it into more networks to fit the quantity of networks 13 00:00:45,379 --> 00:00:50,217 that I need? The 2nd piece of that is, you know, each one 14 00:00:50,217 --> 00:00:52,219 of those networks in your organization is going to 15 00:00:52,219 --> 00:00:55,322 have a certain quantity of hosts in it, right? If 16 00:00:55,322 --> 00:00:57,124 you're creating a network for your engineering 17 00:00:57,124 --> 00:00:59,226 department, if you're creating a network for your 18 00:00:59,226 --> 00:01:01,695 payroll department you're going to have to also be 19 00:01:01,695 --> 00:01:04,998 aware of, okay, not only is that a discrete network that 20 00:01:04,998 --> 00:01:07,834 needs its own group number, its own network number, but 21 00:01:07,834 --> 00:01:11,672 you also need to be aware of how many devices within that 22 00:01:11,672 --> 00:01:15,442 network are going to need discrete IP addresses, how 23 00:01:15,442 --> 00:01:18,312 many hosts will there be in that network. And also, keep 24 00:01:18,312 --> 00:01:21,181 in mind that whatever router is connected to that 25 00:01:21,181 --> 00:01:24,318 network, whatever default gateway is connected to it, 26 00:01:24,318 --> 00:01:28,155 that router counts as a host. That router's 27 00:01:28,155 --> 00:01:30,390 interface connecting to that network is going to need an 28 00:01:30,390 --> 00:01:34,261 IP address itself so he recognizes that he is a host 29 00:01:34,261 --> 00:01:37,097 on the network that is going to consume one of your 30 00:01:37,097 --> 00:01:41,101 available host addresses. So don't forget about that. So 31 00:01:41,101 --> 00:01:43,971 that's the second part of this, is okay, not only do I 32 00:01:43,971 --> 00:01:46,206 need to create my subnets and figure out what my 33 00:01:46,206 --> 00:01:49,810 subnet mask is, but after I create that new subnet mask, 34 00:01:49,810 --> 00:01:53,547 I have to ask myself, These subnets I'm creating, do 35 00:01:53,547 --> 00:01:58,618 they have enough host space left over for the host 36 00:01:58,618 --> 00:02:02,823 requirements I have in each one of these networks. If 37 00:02:02,823 --> 00:02:06,560 the answer is no, well then you can't use this technique 38 00:02:06,560 --> 00:02:08,829 that we're using here. You have to use different 39 00:02:08,829 --> 00:02:10,297 technique that will get into them. We talked about 40 00:02:10,297 --> 00:02:12,599 variable links subnet masking. So how do you 41 00:02:12,599 --> 00:02:14,668 answer that question? How do you say, Okay, given this 42 00:02:14,668 --> 00:02:17,971 particular network, whether it's my starting network or 43 00:02:17,971 --> 00:02:20,440 whether it's a network I've created as a result of 44 00:02:20,440 --> 00:02:23,610 subnetting, how many host addresses do I have 45 00:02:23,610 --> 00:02:27,047 available in this network? And here's the formula to 46 00:02:27,047 --> 00:02:35,622 answer that. You take-- actually hold on a second. 47 00:02:35,622 --> 00:02:39,026 This is incorrect. This is incorrect. I need to change 48 00:02:39,026 --> 00:02:42,229 this. You're not talking about subnetting bits at 49 00:02:42,229 --> 00:02:47,934 this point. You're talking about host bits. There we 50 00:02:47,934 --> 00:02:55,342 go. That is more accurate. To the power of H minus 2. 51 00:02:55,342 --> 00:03:00,881 So when the determining how many subnets am I going to 52 00:03:00,881 --> 00:03:03,417 have available. You took a look at those bits you converted 53 00:03:03,417 --> 00:03:06,386 into subnet bits. Like I converted 3 bits in a 54 00:03:06,386 --> 00:03:08,622 subnetting bits, and I said, "Well, with 3 bits of 55 00:03:08,622 --> 00:03:12,859 subnetting, 2 to the power of 3 gives me 8 combinations 56 00:03:12,859 --> 00:03:15,929 - 8 networks I could have." Now, you're taking your 57 00:03:15,929 --> 00:03:19,566 gaze, your focus, and you're shifting it away from your 58 00:03:19,566 --> 00:03:21,501 networking bits, and now you're looking at the bits 59 00:03:21,501 --> 00:03:23,904 that are left. You're looking at your host bits 60 00:03:23,904 --> 00:03:26,440 that are leftover, and you're saying, "Okay, how 61 00:03:26,440 --> 00:03:30,677 many host bits do I have?" If I've got 9 host bits 62 00:03:30,677 --> 00:03:32,679 leftover, if each one of those subnets I've created 63 00:03:32,679 --> 00:03:36,817 has 9 host bits leftover at the end, I say, "Well, with 64 00:03:36,817 --> 00:03:42,789 9 host bits, 2 to the power of 9 minus 2 gives me how 65 00:03:42,789 --> 00:03:45,258 many host I have available?" Now you might be wondering, 66 00:03:45,258 --> 00:03:48,562 well why minus 2? Well, the last part of the slide here 67 00:03:48,562 --> 00:03:52,532 demonstrates that because remember, of your host bits 2 68 00:03:52,532 --> 00:03:56,603 of those available patters are not accessible for 69 00:03:56,603 --> 00:04:02,742 assigning to hosts. The all 0s host and the all 1s host, the 70 00:04:02,742 --> 00:04:05,946 network and the broadcast are not usable. So that's 71 00:04:05,946 --> 00:04:08,849 why you don't have every possible combination of hosts 72 00:04:08,849 --> 00:04:12,986 available. You have every possible combination but 2 73 00:04:12,986 --> 00:04:16,923 minus 2, so 2 to the power of H minus 2 gives you your 74 00:04:16,923 --> 00:04:28,768 available hosts. So, based on that, let's do a few more 75 00:04:28,768 --> 00:04:34,107 examples, or I should say, a few more exercises. Get 76 00:04:34,107 --> 00:04:41,581 everything lined up here. All right, so here we go. 77 00:04:41,581 --> 00:04:47,988 Given the following subnet mask, how many hosts can fit 78 00:04:47,988 --> 00:04:51,591 in this subnet? What's the total quantity of host you 79 00:04:51,591 --> 00:04:56,129 have available based on this subnet mask? So in this 80 00:04:56,129 --> 00:05:02,602 particular example, our correct answer is B, 62 81 00:05:02,602 --> 00:05:08,108 hosts. So with this particular subnet mask, it's 82 00:05:08,108 --> 00:05:11,745 telling us that of our entire 32-bit address, most 83 00:05:11,745 --> 00:05:17,584 of it, 26 bits, are networking bits, are 84 00:05:17,584 --> 00:05:20,086 reserved for the network, for the group, which only 85 00:05:20,086 --> 00:05:26,226 leaves us with six bits left over for host bits. Well, 2 86 00:05:26,226 --> 00:05:30,897 to the power of 6 gives us the number 64, and when we 87 00:05:30,897 --> 00:05:40,207 subtract 2 from that, that gives us 62. So another one. 88 00:05:40,207 --> 00:05:44,044 An ISP leases you the following network. You need 89 00:05:44,044 --> 00:05:49,816 to create 22 subnetworks from this single network. 90 00:05:49,816 --> 00:05:53,153 What will be your new subnet mask, and how many hosts 91 00:05:53,153 --> 00:06:04,130 will be supported in each subnet? All right, so the 92 00:06:04,130 --> 00:06:09,836 answers for this are A and E. Good job for those of you 93 00:06:09,836 --> 00:06:18,011 who selected that. So with 22 subnetworks. Okay, so 94 00:06:18,011 --> 00:06:20,981 let's see 1 stealing 1-bit will give me 2 networks, 4 95 00:06:20,981 --> 00:06:26,319 networks, 8, 16, almost there, 32. So I need to 96 00:06:26,319 --> 00:06:31,825 steal 5-bits to give myself at least 22 networks. So if 97 00:06:31,825 --> 00:06:36,696 I take 5-bits and I add it to a slash 23, 23 plus 5 is 98 00:06:36,696 --> 00:06:42,469 a slash 28. And with a slash 28, that will give me the 99 00:06:42,469 --> 00:06:45,505 first subnet mask, 255.255.255, that gives me 100 00:06:45,505 --> 00:06:50,543 24-bits. And then 240, if I draw that on here, that's 101 00:06:50,543 --> 00:07:01,955 1.1, that's 224 plus 1, so that gives me my 28-bits. 102 00:07:01,955 --> 00:07:08,061 First 23 plus the 5 bits that I stole gives me 28 103 00:07:08,061 --> 00:07:15,502 bits, which leaves me with four host bits left over. 104 00:07:15,502 --> 00:07:20,040 Two to the power of four minus two gives you 14 105 00:07:20,040 --> 00:07:26,680 hosts. An ISP leases you the following network. You need 106 00:07:26,680 --> 00:07:30,417 to create 22 subnetworks from this single network. 107 00:07:30,417 --> 00:07:33,453 See if you can answer all four of those questions. 108 00:07:33,453 --> 00:07:44,064 [silence] Okay. I gave you a little bit of extra time on 109 00:07:44,064 --> 00:07:46,599 that one because it's basically four questions 110 00:07:46,599 --> 00:07:51,538 rolled into one. Here are the answers. 111 00:07:59,446 --> 00:08:04,918 Okay, so we start out with the /24 to make 22 networks 112 00:08:04,918 --> 00:08:07,921 out of that. It was just basically like the previous 113 00:08:07,921 --> 00:08:12,625 question, that also has 22 networks. We needed to steal 114 00:08:12,625 --> 00:08:21,701 how many bits, 2, 4, 8, 16. We need to steal 5-bits, 2 115 00:08:21,701 --> 00:08:26,506 to the power 5, gives us 32. So that gave us our new subnet 116 00:08:26,506 --> 00:08:34,147 mask of /29. Which in dotted decimal is this. It 117 00:08:34,147 --> 00:08:40,186 tells us the first 29-bits, our networking bits. With the 118 00:08:40,186 --> 00:08:48,695 /29, that means we have 3 host bits left over. 2 to 119 00:08:48,695 --> 00:08:58,805 the power of 3 is 8 minus 2 is 6 hosts. What is the 120 00:08:58,805 --> 00:09:04,110 subnet address of the 4th subnet? Let me actually show 121 00:09:04,110 --> 00:09:07,113 you I've been holding off on this little tidbit until 122 00:09:07,113 --> 00:09:10,984 now, a little cheat sheet I developed to help identify 123 00:09:10,984 --> 00:09:15,955 this kind of thing. Right here, this is what I call my 124 00:09:15,955 --> 00:09:17,757 subnetting cheat sheet. Everybody's got a different 125 00:09:17,757 --> 00:09:19,926 way of doing this. You'll probably find dozens of 126 00:09:19,926 --> 00:09:22,729 similar types of things if you Google it, but this is 127 00:09:22,729 --> 00:09:27,400 just one I came up with. This is the way I work it. 128 00:09:27,400 --> 00:09:32,005 So in the previous example we figured out it said I 129 00:09:32,005 --> 00:09:39,679 needed 22 subnetworks. So if I use this I say, okay, well 130 00:09:39,679 --> 00:09:42,081 the numbers in green here represent how many networks 131 00:09:42,081 --> 00:09:45,819 are available. So if I need 22 subnetworks that means 132 00:09:45,819 --> 00:09:51,858 I'd have to go out to right here, so that means I would 133 00:09:51,858 --> 00:09:58,465 need a /29 so putting my dividing line right here 134 00:09:58,465 --> 00:10:04,204 gives me 32 networks so /29, and then if I look just to 135 00:10:04,204 --> 00:10:07,574 the right of that line that gives me how many hosts 136 00:10:07,574 --> 00:10:11,678 are available. So basically the way you create this from 137 00:10:11,678 --> 00:10:14,447 scratch is this, and this is really useful if you're just 138 00:10:14,447 --> 00:10:19,652 subnetting into the last octet, into the 4th octet. 139 00:10:19,652 --> 00:10:21,488 You just say, Okay in that 4th octet, let me just put 140 00:10:21,488 --> 00:10:25,492 my numbers in binary here, 1, 2, 4, 8, 16 so on and so 141 00:10:25,492 --> 00:10:32,932 forth, then draw lines separating each bit. And so 142 00:10:32,932 --> 00:10:35,969 for here you can see, Okay, well if I steal 1-bit that's 143 00:10:35,969 --> 00:10:39,772 a slash 25, if I steal 2-bits it's a slash 26. So 144 00:10:39,772 --> 00:10:42,008 that's where you count the blue numbers up here. This 145 00:10:42,008 --> 00:10:45,645 is your shorthand notation for your subnets. And you 146 00:10:45,645 --> 00:10:48,147 can see here, Okay, now I just started doing binary 2, 147 00:10:48,147 --> 00:10:52,085 4, 8, 16, 32. This tells me, Okay, if my-- if I have a 148 00:10:52,085 --> 00:10:55,355 /25 it gives me 2 networks. If I have a /30 149 00:10:55,355 --> 00:10:59,025 it gives me 64 networks. If I have a /27, 8 150 00:10:59,025 --> 00:11:02,428 networks. So now you've developed how many networks 151 00:11:02,428 --> 00:11:06,666 you get for each one of these subnet masks and then 152 00:11:06,666 --> 00:11:09,602 you take a look at your original binary number, 153 00:11:09,602 --> 00:11:12,805 subtract 2 from it, and put it to the right of the line. 154 00:11:12,805 --> 00:11:16,442 Remember, from the right rear most we discover our 155 00:11:16,442 --> 00:11:21,347 hosts. So, that gives me 126. 64 minus 2 is 62. 32 156 00:11:21,347 --> 00:11:26,219 minus 2 is 30. So now once I've decided what my line is 157 00:11:26,219 --> 00:11:29,722 going to be I can look to the left of it to discover 158 00:11:29,722 --> 00:11:32,125 how many networks I have available and I can look to 159 00:11:32,125 --> 00:11:35,395 the right of it to discover how many hosts I have 160 00:11:35,395 --> 00:11:39,899 available given that particular subnet mask. So 161 00:11:39,899 --> 00:11:45,004 in this particular case when we saw that I had-- let's 162 00:11:45,004 --> 00:11:48,675 see, let's go back to here - when I was going to be doing 163 00:11:48,675 --> 00:11:57,951 a /29, right? 255.255.255.240 that's /29. 164 00:11:57,951 --> 00:12:00,186 So right here with the /29 when I looked just to the 165 00:12:00,186 --> 00:12:05,592 right of the line. That gives me six hosts and 166 00:12:05,592 --> 00:12:09,963 indeed that was this correct answer right here, six 167 00:12:09,963 --> 00:12:13,299 hosts. Now one other thing you can use this for was the 168 00:12:13,299 --> 00:12:16,669 subnet address of the fourth subnet. If I go back to 169 00:12:16,669 --> 00:12:20,740 this, once I know where my dividing line is, like for 170 00:12:20,740 --> 00:12:23,443 example, /29, the dividing line is right here between 171 00:12:23,443 --> 00:12:27,213 where the network ends and where the hosts begin. Look 172 00:12:27,213 --> 00:12:30,116 at the binary number just to the left of that line. In 173 00:12:30,116 --> 00:12:33,119 this particular case, it's the number eight. This tells 174 00:12:33,119 --> 00:12:37,824 you that all of your subnets are going to be in multiples 175 00:12:37,824 --> 00:12:42,262 or increments of eight. For example, you're going to 176 00:12:42,262 --> 00:12:46,833 start out with subnet 0, 00000, and then it's going 177 00:12:46,833 --> 00:12:53,306 to be 00001. Well that's number eight. 00010, that's 178 00:12:53,306 --> 00:12:58,044 number 16. 00011, that's the number 24. What do they 179 00:12:58,044 -a subnet mask that was a slash twenty-seven, well 0:13:06.880000 --> 0:13:10.160000 just looking to the left of this line, all of your subnets are going to 0:13:10.160000 --> 0:13:13.220000 be in multiples of thirty-twos. 0:13:13.220000 --> 0:13:17.000000 They're all going to be in multiples of thirty-twos. 0:13:17.000000 --> 0:13:26.260000 So in our particular case, where's my cursor, there it is, we came up 0:13:26.260000 --> 0:13:42.760000 with 255, 255, 255.248, which was equivalent to a slash twenty-nine. 0:13:42.760000 --> 0:14:07.480000 So there's my last octet put into my binary numbers. 0:14:07.480000 --> 0:14:09.560000 Nope, hold on a second. 0:14:09.560000 --> 0:14:11.140000 I think I'm missing something. 0:14:11.140000 --> 0:14:16.160000 I think I only had seven patterns. 0:14:16.160000 --> 0:14:23.240000 One, two, three, four, five, six, seven, eight. 0:14:23.240000 --> 0:14:25.160000 All right, there we go. 0:14:25.160000 --> 0:14:41.400000 So here we've got 128, 64, 32, 16, eight, four, two, and one. 0:14:41.400000 --> 0:14:47.160000 Okay, and when I put my dividing line as a slash twenty-nine, which was 0:14:47.160000 --> 0:14:55.700000 right here, I've got twenty-four bits plus five slash twenty-nine. 0:14:55.700000 --> 0:15:01.700000 Now I know that all of my networks are going to be in increments or multiples 0:15:01.700000 --> 0:15:08.700000 of eight. So my first network, see what they say, the original starting 0:15:08.700000 --> 0:15:11.920000 network was 199.10.1. 0:15:11.920000 --> 0:15:20.300000 199.10.1. And I can't change that. 0:15:20.300000 --> 0:15:26.520000 So the first network is going to be .0, that's my first subnet. 0:15:26.520000 --> 0:15:30.760000 And now my next one in multiples of eight is going to be that. 0:15:30.760000 --> 0:15:35.280000 My next multiple of eight is going to be that. 0:15:35.280000 --> 0:15:43.660000 That's going to be my next multiple of eight there. 0:15:43.660000 --> 0:15:47.960000 Let's just do one more. 0:15:47.960000 --> 0:15:50.000000 That's my next multiple of eight. 0:15:50.000000 --> 0:15:56.140000 And the question was, what is the subnet address of the fourth subnet? 0:15:56.140000 --> 0:15:58.080000 Well, we just figured that out. 0:15:58.080000 --> 0:16:01.140000 Here's the first, second, third. 0:16:01.140000 --> 0:16:07.200000 So this was the subnet address of the fourth subnet right there, 10.1 0:16:07.200000 --> 0:16:10.740000 .24. That's what led to this. 0:16:10.740000 --> 0:16:14.780000 What is the broadcast address of the sixth subnet? 0:16:14.780000 --> 0:16:16.400000 Okay, well let's keep going. 0:16:16.400000 --> 0:16:18.080000 We've already got the fifth one. 0:16:18.080000 --> 0:16:24.900000 The sixth one will be that. 0:16:24.900000 --> 0:16:28.500000 Let's just go one more to the seventh one. 0:16:28.500000 --> 0:16:38.240000 That's the seventh subnet. 0:16:38.240000 --> 0:16:46.760000 So if this is the IP address, if 1 .48 is the IP address of the seventh 0:16:46.760000 --> 0:16:53.800000 subnet in binary, one less than that would be the broadcast address or 0:16:53.800000 --> 0:16:58.100000 the very last address of the previous network. 0:16:58.100000 --> 0:17:00.480000 Well, what's one less than that? 0:17:00.480000 --> 0:17:12.880000 199.10.1.47. So that is the broadcast address of the previous or the sixth 0:17:12.880000 --> 0:17:22.440000 subnet. And that's what gave us this number. 0:17:22.440000 --> 0:17:26.680000 So if you didn't have a chance, let me let you take a screenshot of that 0:17:26.680000 --> 0:17:37.800000 for a moment. I'll get rid of this circle here. 0:17:37.800000 --> 0:17:49.400000 And using that, let's see how well you fare on this next question. 0:17:49.400000 --> 0:17:50.500000 Same type of question. 0:17:50.500000 --> 0:17:55.460000 Go ahead and read through that. 0:17:55.460000 --> 0:18:00.080000 So let's go through each one of these. 0:18:00.080000 --> 0:18:06.220000 So we need 59 subnetworks from the single network. 0:18:06.220000 --> 0:18:10.320000 Okay, so let's just use my fingers here. 0:18:10.320000 --> 0:18:13.740000 248, 16, 32, 64. 0:18:13.740000 --> 0:18:16.060000 So I'm going to need to steal six bits. 0:18:16.060000 --> 0:18:20.240000 So if I take my original 21 bits and I add six bits to it, that gets me 0:18:20.240000 --> 0:18:25.820000 a slash 27. So let's go over here. 0:18:25.820000 --> 0:18:30.380000 And we'll just put a red circle around slash 27. 0:18:30.380000 --> 0:18:32.540000 So that's where we are. 0:18:32.540000 --> 0:18:38.060000 So based on that, what will be our new subnet mask? 0:18:38.060000 --> 0:18:43.800000 255, 255, 255.224. 0:18:43.800000 --> 0:18:46.540000 That's equivalent to a slash 27. 0:18:46.540000 --> 0:18:49.380000 How many hosts will be supported in each subnet? 0:18:49.380000 --> 0:18:51.760000 Well, take a look at this. 0:18:51.760000 --> 0:18:54.100000 Go down to the bottom right. 0:18:54.100000 --> 0:18:57.440000 30 hosts. That's the number just to the right of that line. 0:18:57.440000 --> 0:19:05.220000 30 hosts. What will be the subnet address of the fourth subnet? 0:19:05.220000 --> 0:19:09.740000 Well, looking at this with a slash 27, my subnets are always in increments 0:19:09.740000 --> 0:19:13.280000 or multiples of 32s. 0:19:13.280000 --> 0:19:18.880000 So the first subnet will be the zero subnet and then the 32 subnet, the 0:19:18.880000 --> 0:19:25.900000 64 subnet, and the fourth subnet will be the 96 subnet. 0:19:25.900000 --> 0:19:32.240000 The 96 subnet. What will be the broadcast address of the sixth subnet? 0:19:32.240000 --> 0:19:36.460000 Well, if we kept on going adding 32 plus 32 plus 32, if we went up to 0:19:36.460000 --> 0:19:42.520000 the seventh subnet, we would have seen that that was the 8.192 network. 0:19:42.520000 --> 0:19:47.320000 And if we back off one from that, that gives us .191, which would be the 0:19:47.320000 --> 0:19:51.040000 broadcast address of the previous or the sixth subnet. 0:19:51.040000 --> 0:19:52.320000 It was right before it.