1 1 00:00:00,550 --> 00:00:02,130 In this video, I'm going to show you 2 2 00:00:02,130 --> 00:00:04,140 how to do subnetting by hand. 3 3 00:00:04,140 --> 00:00:06,230 This way, we can eliminate all of the math 4 4 00:00:06,230 --> 00:00:07,560 and all of the pen and paper 5 5 00:00:07,560 --> 00:00:10,120 and be able to get the answers we need really quickly. 6 6 00:00:10,120 --> 00:00:11,580 It's really just a shortcut. 7 7 00:00:11,580 --> 00:00:12,830 In the last couple of videos, 8 8 00:00:12,830 --> 00:00:14,360 I showed you how everything worked 9 9 00:00:14,360 --> 00:00:16,530 so that you understand the theory behind it all, 10 10 00:00:16,530 --> 00:00:19,230 but now, we're going to get to the quick way of doing it. 11 11 00:00:19,230 --> 00:00:21,420 So, when I subnet by hand to do this demonstration, 12 12 00:00:21,420 --> 00:00:23,590 I'm going to wear my subnetting gloves. 13 13 00:00:23,590 --> 00:00:25,060 Now, my subnetting gloves are special 14 14 00:00:25,060 --> 00:00:26,390 because I have little numbers 15 15 00:00:26,390 --> 00:00:27,440 written on the backside of them 16 16 00:00:27,440 --> 00:00:29,220 that I'm going to show you here. 17 17 00:00:29,220 --> 00:00:31,170 You may see here on my subnetting gloves 18 18 00:00:31,170 --> 00:00:33,070 that I have numbers written on them. 19 19 00:00:33,070 --> 00:00:35,440 Now, in the real world, you're not going to have your gloves on 20 20 00:00:35,440 --> 00:00:37,800 but you can memorize these numbers fairly easily. 21 21 00:00:37,800 --> 00:00:39,620 They're just multiples of two. 22 22 00:00:39,620 --> 00:00:41,540 Now if I'm going to start on my right, 23 23 00:00:41,540 --> 00:00:43,330 which on your screen is going to look like the left, 24 24 00:00:43,330 --> 00:00:47,320 you'll see I have two, four, eight, 16, 25 25 00:00:47,320 --> 00:00:51,530 32, 64, 128, and 256 written down. 26 26 00:00:51,530 --> 00:00:53,940 This tells me how many networks there are. 27 27 00:00:53,940 --> 00:00:56,380 This goes back to our two to the nth power, 28 28 00:00:56,380 --> 00:00:59,600 which was our formula that we used when we did this by hand. 29 29 00:00:59,600 --> 00:01:03,170 So, if I asked you if you had a /26 network, 30 30 00:01:03,170 --> 00:01:06,310 how many subnets can be put into a /26 31 31 00:01:06,310 --> 00:01:09,010 if you were given a /24 to start with? 32 32 00:01:09,010 --> 00:01:10,990 Well, if I have a /24 to start with, 33 33 00:01:10,990 --> 00:01:12,670 I'm going to start counting up from there. 34 34 00:01:12,670 --> 00:01:17,670 So, my first finger is going to be /25 and then /26. 35 35 00:01:17,980 --> 00:01:22,330 Since I asked for /26, you can see the number is four. 36 36 00:01:22,330 --> 00:01:23,840 Now, we can do it the other way 37 37 00:01:23,840 --> 00:01:26,310 and we can go from my left to right. 38 38 00:01:26,310 --> 00:01:27,290 In your case, 39 39 00:01:27,290 --> 00:01:28,860 it's going to be your right side of the screen to your left. 40 40 00:01:28,860 --> 00:01:32,350 And this is going to tell me how many hosts or IPs I can have 41 41 00:01:32,350 --> 00:01:33,640 inside of a network. 42 42 00:01:33,640 --> 00:01:35,850 So, if I start from the other side 43 43 00:01:35,850 --> 00:01:39,580 and I start with a /24, I have 256. 44 44 00:01:39,580 --> 00:01:40,413 /25, I have 128. 45 45 00:01:42,071 --> 00:01:43,153 If I have a /26, that's 64. 46 46 00:01:45,098 --> 00:01:47,588 /27, that's 32. 47 47 00:01:47,588 --> 00:01:50,136 /28, that's 16. 48 48 00:01:50,136 --> 00:01:52,466 /29, that's eight. 49 49 00:01:52,466 --> 00:01:53,980 /30, that's four. 50 50 00:01:53,980 --> 00:01:57,260 /31, that's two. 51 51 00:01:57,260 --> 00:01:58,590 So, you can see how this works 52 52 00:01:58,590 --> 00:02:00,630 going from right to left or left to right 53 53 00:02:00,630 --> 00:02:02,370 to be able to figure out how many networks 54 54 00:02:02,370 --> 00:02:04,180 or how many IPs are available. 55 55 00:02:04,180 --> 00:02:07,203 Now, we're going to do a couple of examples using this method. 56 56 00:02:08,130 --> 00:02:09,970 The first one I'm going to use is this one. 57 57 00:02:09,970 --> 00:02:13,510 It's 192.168.0.85. 58 58 00:02:13,510 --> 00:02:15,030 Now, the numbers really don't matter. 59 59 00:02:15,030 --> 00:02:17,930 It's really what's important is that /29 at the end. 60 60 00:02:17,930 --> 00:02:19,430 So, if you want to figure out 61 61 00:02:19,430 --> 00:02:22,030 how many subnets that were in a /29, 62 62 00:02:22,030 --> 00:02:23,410 how would you do that? 63 63 00:02:23,410 --> 00:02:26,270 Well, we're going to count up from right to left, 64 64 00:02:26,270 --> 00:02:28,380 upwards in the multiples of two. 65 65 00:02:28,380 --> 00:02:30,130 So, if I start counting on my fingers, 66 66 00:02:30,130 --> 00:02:35,060 I go 25, 26, 27, 28, 29, 67 67 00:02:35,060 --> 00:02:36,620 and what's on my 29? 68 68 00:02:36,620 --> 00:02:37,820 It's 32. 69 69 00:02:37,820 --> 00:02:41,930 There are 32 subnets if I'm using a /29 network 70 70 00:02:41,930 --> 00:02:44,600 within a normal class C network. 71 71 00:02:44,600 --> 00:02:47,220 Now, if I'm going to look at this from an IP perspective, 72 72 00:02:47,220 --> 00:02:48,850 I'm going to do it the other way. 73 73 00:02:48,850 --> 00:02:51,020 How many IPs are there in a /29? 74 74 00:02:51,020 --> 00:02:53,523 Well, we're going to start with /24, 256. 75 75 00:02:54,708 --> 00:02:58,750 /25, 26, 27, 28, 29, 76 76 00:02:58,750 --> 00:03:01,360 and there, you'll see I have eight IPs. 77 77 00:03:01,360 --> 00:03:03,460 Now, if you remember from our lessons, 78 78 00:03:03,460 --> 00:03:05,330 you always have a broadcast 79 79 00:03:05,330 --> 00:03:06,970 and you always have a network name. 80 80 00:03:06,970 --> 00:03:10,010 So, really, I have six usable IPs for host. 81 81 00:03:10,010 --> 00:03:12,170 I have the first IP which is my network 82 82 00:03:12,170 --> 00:03:14,410 and my last IP which is my broadcast, 83 83 00:03:14,410 --> 00:03:16,270 giving us a total of eight. 84 84 00:03:16,270 --> 00:03:19,083 Again, that's at /29, that's eight. 85 85 00:03:19,930 --> 00:03:24,930 The next problem we have is 192.168.1.25 /28. 86 86 00:03:25,800 --> 00:03:29,930 So, from doing /28, how many subnets and how many IPs? 87 87 00:03:29,930 --> 00:03:32,670 Well, let's pull out our gloves again and we'll start. 88 88 00:03:32,670 --> 00:03:37,670 We have /25, /26, /27, /28, 89 89 00:03:38,060 --> 00:03:41,280 and the /28 has 16 on it. 90 90 00:03:41,280 --> 00:03:43,810 Now, if I go the other way for how many IPs, 91 91 00:03:43,810 --> 00:03:48,300 I'm going to go /24, /25, /26, /27, /28. 92 92 00:03:50,180 --> 00:03:51,710 It's also 16. 93 93 00:03:51,710 --> 00:03:55,130 So, we have 16 subnets and 16 available IPs. 94 94 00:03:55,130 --> 00:03:56,600 You could see how this works. 95 95 00:03:56,600 --> 00:03:58,250 It makes it really easy. 96 96 00:03:58,250 --> 00:03:59,940 So, I think you're getting the idea here 97 97 00:03:59,940 --> 00:04:01,370 but let's try two more. 98 98 00:04:01,370 --> 00:04:03,510 This next one has a /30. 99 99 00:04:03,510 --> 00:04:06,120 So, how many subnets and how many IPs? 100 100 00:04:06,120 --> 00:04:07,800 Well, let's pull out our gloves again 101 101 00:04:07,800 --> 00:04:12,800 and so, we have /25, /26, /27, 28, 29, and 30, 102 102 00:04:13,720 --> 00:04:17,240 and on 30, you see 64 because we counted up, 103 103 00:04:17,240 --> 00:04:21,070 two, four, eight, 16, 32, 64. 104 104 00:04:21,070 --> 00:04:22,040 And so, by doing that, 105 105 00:04:22,040 --> 00:04:24,470 we now know we have 64 subnets. 106 106 00:04:24,470 --> 00:04:25,940 That's what a /30 is. 107 107 00:04:25,940 --> 00:04:28,680 I could take 256 IPs in a class C 108 108 00:04:28,680 --> 00:04:31,390 and I could break it up 64 different times. 109 109 00:04:31,390 --> 00:04:33,440 Now, how many IPs is that going to be? 110 110 00:04:33,440 --> 00:04:35,540 Well, that's 256 divided by 64 111 111 00:04:35,540 --> 00:04:37,650 but if we use our gloves, we can go the other way, 112 112 00:04:37,650 --> 00:04:42,650 24, 25, 26, 27, 28, 29, 30, and it's four, four IPs. 113 113 00:04:44,440 --> 00:04:47,370 Because we have four IPs and 64 subnets, 114 114 00:04:47,370 --> 00:04:50,120 that's going to give us 256 total. 115 115 00:04:50,120 --> 00:04:51,080 Let's try another one. 116 116 00:04:51,080 --> 00:04:53,300 This one's going to be a /31. 117 117 00:04:53,300 --> 00:04:55,760 Now, a /31, that's not even on the table 118 118 00:04:55,760 --> 00:04:57,340 you told me to memorize, Jason. 119 119 00:04:57,340 --> 00:04:58,173 That's right. 120 120 00:04:58,173 --> 00:04:59,900 That's because it's a nonstandard one 121 121 00:04:59,900 --> 00:05:01,550 but Cisco does support it. 122 122 00:05:01,550 --> 00:05:03,910 It's usually used for point-to-point connections. 123 123 00:05:03,910 --> 00:05:06,400 So, if I'm going to connect one router to another router 124 124 00:05:06,400 --> 00:05:07,997 and I don't need to have a network 125 125 00:05:07,997 --> 00:05:10,910 and a broadcast in that case with Cisco devices, 126 126 00:05:10,910 --> 00:05:14,220 I can use a /31 so I'll only use two IPs 127 127 00:05:14,220 --> 00:05:17,260 instead of the four that we had in the last /30 example 128 128 00:05:17,260 --> 00:05:19,030 which is normally used for point-to-point. 129 129 00:05:19,030 --> 00:05:20,630 But again, if we pull out our hands, 130 130 00:05:20,630 --> 00:05:21,463 we could start going 131 131 00:05:21,463 --> 00:05:23,780 and figuring out how many subnets and how many IPs. 132 132 00:05:23,780 --> 00:05:25,203 So, let's do that. 133 133 00:05:26,102 --> 00:05:29,930 /25, 26, 27, 28, 29, 30, 31, 134 134 00:05:29,930 --> 00:05:31,810 so, that tells me it's on my seventh finger. 135 135 00:05:31,810 --> 00:05:33,320 So, if I didn't have my gloves on, 136 136 00:05:33,320 --> 00:05:34,970 I would just do powers of two. 137 137 00:05:34,970 --> 00:05:39,430 Two, four, eight, 16, 32, 64, 128, 138 138 00:05:39,430 --> 00:05:41,550 and so, that seventh finger is 128. 139 139 00:05:41,550 --> 00:05:43,560 There's 128 subnets. 140 140 00:05:43,560 --> 00:05:45,230 Now, I'm sure you can do the math here. 141 141 00:05:45,230 --> 00:05:47,950 If there's 256 total IPs in a class C 142 142 00:05:47,950 --> 00:05:50,150 and we just took up 128 subnets, 143 143 00:05:50,150 --> 00:05:52,380 that means, there's going to be two IPs per subnet. 144 144 00:05:52,380 --> 00:05:53,920 So, let's do it with our hands anyway 145 145 00:05:53,920 --> 00:05:55,910 just because that's what we're doing in this video 146 146 00:05:55,910 --> 00:05:56,840 and so, here we go. 147 147 00:05:56,840 --> 00:06:01,840 We're going to go 24, 25, 26, 27, 28, 29, 30, and 31, 148 148 00:06:02,750 --> 00:06:05,570 and on 31, we have a two, right? 149 149 00:06:05,570 --> 00:06:08,740 We can do that if we went and counted up or counted down. 150 150 00:06:08,740 --> 00:06:13,740 256, 128, 64, 32, 16, eight, four, and two, 151 151 00:06:15,280 --> 00:06:17,390 and that gets us to that same number of two. 152 152 00:06:17,390 --> 00:06:19,580 So, it's all about memorizing these multiples of two 153 153 00:06:19,580 --> 00:06:20,820 as we go through this. 154 154 00:06:20,820 --> 00:06:23,820 Again, a /31 is something that's Cisco supported. 155 155 00:06:23,820 --> 00:06:26,220 Some of the other routers are starting to support it 156 156 00:06:26,220 --> 00:06:28,960 but it is something that is mainly a Cisco thing. 157 157 00:06:28,960 --> 00:06:31,610 Let's go ahead and do one last one here 158 158 00:06:31,610 --> 00:06:34,040 and this one is going to be a /32. 159 159 00:06:34,040 --> 00:06:35,990 So, when we're doing a /32, 160 160 00:06:35,990 --> 00:06:38,070 you may go do I even need to use my hands? 161 161 00:06:38,070 --> 00:06:39,280 Well, you really don't 162 162 00:06:39,280 --> 00:06:42,490 because a /32 just denotes a single host. 163 163 00:06:42,490 --> 00:06:45,000 If I have your IP address and put /32, 164 164 00:06:45,000 --> 00:06:47,130 it means it's only that IP 165 165 00:06:47,130 --> 00:06:49,560 and so, that really is just one IP 166 166 00:06:49,560 --> 00:06:51,940 and there can be 256 subnets. 167 167 00:06:51,940 --> 00:06:53,300 But if you wanted to use your hands, 168 168 00:06:53,300 --> 00:06:54,410 you could do that, right? 169 169 00:06:54,410 --> 00:06:59,410 Because we have 25, 26, 27, 28, 29, 30, 31, and 32, 170 170 00:07:00,120 --> 00:07:02,900 and you see on 32 it's 256. 171 171 00:07:02,900 --> 00:07:04,390 I think you get the idea here. 172 172 00:07:04,390 --> 00:07:05,670 So, this is how you can do this 173 173 00:07:05,670 --> 00:07:07,750 in a very quick and easy manner. 174 174 00:07:07,750 --> 00:07:09,220 Now, before we finish this video, 175 175 00:07:09,220 --> 00:07:11,230 I do want to put this to practice 176 176 00:07:11,230 --> 00:07:13,910 to some of the things you're going to see on the Network+ exam 177 177 00:07:13,910 --> 00:07:15,410 because you're likely not going to get a question 178 178 00:07:15,410 --> 00:07:17,870 that just says how many subnets or how many IPs. 179 179 00:07:17,870 --> 00:07:20,120 It's going to be a little bit more complicated than that. 180 180 00:07:20,120 --> 00:07:21,840 So, let's go to the next question 181 181 00:07:21,840 --> 00:07:23,560 and you're going to be able to see what we have. 182 182 00:07:23,560 --> 00:07:27,130 So, in this case, I have 171.129.67.160 /25 183 183 00:07:30,180 --> 00:07:32,150 and the question I have for you is, 184 184 00:07:32,150 --> 00:07:33,590 what's the network IP? 185 185 00:07:33,590 --> 00:07:34,800 What's the first host? 186 186 00:07:34,800 --> 00:07:35,840 What's the last host? 187 187 00:07:35,840 --> 00:07:37,780 And what's the broadcast? 188 188 00:07:37,780 --> 00:07:40,180 So, let's pull out our gloves and take a look at this. 189 189 00:07:40,180 --> 00:07:43,010 So, if I pull out my gloves and I go for the first one, 190 190 00:07:43,010 --> 00:07:45,710 a /25 is two subnets. 191 191 00:07:45,710 --> 00:07:47,330 Now, with two subnets, 192 192 00:07:47,330 --> 00:07:50,190 that means if I'm using 256 IPs, 193 193 00:07:50,190 --> 00:07:51,860 remember, I told you on the Network+ exam, 194 194 00:07:51,860 --> 00:07:53,690 we're always going to assume that we're doing this 195 195 00:07:53,690 --> 00:07:56,710 in terms of a /24 or greater 196 196 00:07:56,710 --> 00:07:58,880 because that's usually what you're going to see on the exam. 197 197 00:07:58,880 --> 00:08:03,280 So, in this case, we're going to start with /24, is 256 IPs. 198 198 00:08:03,280 --> 00:08:07,150 Because this is a /25, I'm going to have two subnets. 199 199 00:08:07,150 --> 00:08:10,230 So, I take that 256 and I break it in half, right? 200 200 00:08:10,230 --> 00:08:13,490 So, if I have two subnets, what's the first subnet going to be? 201 201 00:08:13,490 --> 00:08:15,710 Well, it's going to start at .0. 202 202 00:08:15,710 --> 00:08:17,670 What's the second subnet going to be? 203 203 00:08:17,670 --> 00:08:21,370 It's going to start at 128 because we have 128 IPs. 204 204 00:08:21,370 --> 00:08:24,990 So, the first one goes from zero to 127 205 205 00:08:24,990 --> 00:08:28,590 and the second one is going to go from 128 to 255, 206 206 00:08:28,590 --> 00:08:30,580 which gives us our network ID. 207 207 00:08:30,580 --> 00:08:32,990 Our network ID is 171.129.67.128 208 208 00:08:35,920 --> 00:08:39,650 and our broadcast ID is going to be .255. 209 209 00:08:39,650 --> 00:08:42,410 So, what's our first host and our last host? 210 210 00:08:42,410 --> 00:08:44,567 Well, it's going to be .29 211 211 00:08:44,567 --> 00:08:47,140 and our last host is going to be .254 212 212 00:08:47,140 --> 00:08:48,290 because our first host is always 213 213 00:08:48,290 --> 00:08:50,200 one above what the network was 214 214 00:08:50,200 --> 00:08:51,300 and our last host is always 215 215 00:08:51,300 --> 00:08:53,600 one below what the broadcast was. 216 216 00:08:53,600 --> 00:08:54,570 That's how this works 217 217 00:08:54,570 --> 00:08:55,810 when you're just doing it with your hands. 218 218 00:08:55,810 --> 00:08:57,780 It makes it very quick and easy. 219 219 00:08:57,780 --> 00:08:59,090 Let's try another one. 220 220 00:08:59,090 --> 00:09:04,090 The next one we have is 56.187.210.21 /28. 221 221 00:09:05,120 --> 00:09:07,320 So, if I want to take a /28, 222 222 00:09:07,320 --> 00:09:10,070 we want to ask how many subnets and how many IP addresses 223 223 00:09:10,070 --> 00:09:10,990 cause that's going to help us 224 224 00:09:10,990 --> 00:09:13,580 write down what our network and broadcast are 225 225 00:09:13,580 --> 00:09:14,590 and that helps us figure out 226 226 00:09:14,590 --> 00:09:16,280 our first host and our last host. 227 227 00:09:16,280 --> 00:09:18,600 So, if we have a /28, we'll pull out our gloves 228 228 00:09:18,600 --> 00:09:21,467 and we'll go 25, 26, 27, 28, 229 229 00:09:21,467 --> 00:09:26,467 and 28 is my pinky which is a 16 so there are 16 subnets. 230 230 00:09:27,090 --> 00:09:30,080 Now, if I go the other way, how many IPs are there? 231 231 00:09:30,080 --> 00:09:33,710 Well, 24, 25, 26, 27, 28. 232 232 00:09:33,710 --> 00:09:36,360 There's also 16 IPs. 233 233 00:09:36,360 --> 00:09:39,140 So, 16 IPs and 16 subnets. 234 234 00:09:39,140 --> 00:09:40,740 Now, if you take those 16 IPs, 235 235 00:09:40,740 --> 00:09:44,160 you're going to go zero through 15, that's the first range, 236 236 00:09:44,160 --> 00:09:47,310 16 through 31, that's the second range. 237 237 00:09:47,310 --> 00:09:49,050 If we look at our IP address we were given, 238 238 00:09:49,050 --> 00:09:51,090 it ended in .21. 239 239 00:09:51,090 --> 00:09:52,270 Where does that fall? 240 240 00:09:52,270 --> 00:09:55,920 Well, it falls in that second range from 16 to 31. 241 241 00:09:55,920 --> 00:10:00,430 So, our network is 56.187.210.16. 242 242 00:10:00,430 --> 00:10:04,710 Our broadcast is 56.187.210.31. 243 243 00:10:04,710 --> 00:10:06,380 And then, we take our last host, 244 244 00:10:06,380 --> 00:10:08,870 which is one less than the broadcast .30, 245 245 00:10:08,870 --> 00:10:12,670 and our first host, one more than the network .17. 246 246 00:10:12,670 --> 00:10:14,700 That's how we can do this 247 247 00:10:14,700 --> 00:10:17,270 just using our hands with no pen and paper 248 248 00:10:17,270 --> 00:10:20,840 and we can get these answers very quickly as we go through. 249 249 00:10:20,840 --> 00:10:23,140 I hope this subnetting by hand was helpful 250 250 00:10:23,140 --> 00:10:24,640 and if you didn't get it the first time, 251 251 00:10:24,640 --> 00:10:27,870 go ahead and rewatch the video again cause once it clicks, 252 252 00:10:27,870 --> 00:10:30,840 it makes all of your subnetting problems so easy 253 253 00:10:30,840 --> 00:10:32,330 and so quick to get through 254 254 00:10:32,330 --> 00:10:36,663 and you'll have no issues on the Network+ exam.