1 00:00:01,080 --> 00:00:01,980 In this video, 2 00:00:01,980 --> 00:00:04,710 I'm going to show you how to do subnetting by hand. 3 00:00:04,710 --> 00:00:06,780 This way we can eliminate all of the math 4 00:00:06,780 --> 00:00:08,130 and all of the pen and paper 5 00:00:08,130 --> 00:00:10,650 and be able to get the answers we need really quickly. 6 00:00:10,650 --> 00:00:12,120 It's really just a shortcut. 7 00:00:12,120 --> 00:00:13,380 In the last couple of videos, 8 00:00:13,380 --> 00:00:14,910 I showed you how everything worked 9 00:00:14,910 --> 00:00:17,070 so that you understand the theory behind it all. 10 00:00:17,070 --> 00:00:19,770 But now we're going to get to the quick way of doing it. 11 00:00:19,770 --> 00:00:21,960 So when I subnet by hand to do this demonstration, 12 00:00:21,960 --> 00:00:24,150 I'm going to wear my subnetting gloves. 13 00:00:24,150 --> 00:00:25,620 Now, my subnetting gloves are special 14 00:00:25,620 --> 00:00:28,020 because I have little numbers written on the backside of 'em 15 00:00:28,020 --> 00:00:29,820 that I'm going to show you here. 16 00:00:29,820 --> 00:00:31,890 So you may see here on my subnetting gloves 17 00:00:31,890 --> 00:00:33,810 that I have numbers written on them. 18 00:00:33,810 --> 00:00:34,830 Now, in the real world, 19 00:00:34,830 --> 00:00:36,150 you're not going to have your gloves on, 20 00:00:36,150 --> 00:00:38,250 but you can memorize these numbers fairly easily. 21 00:00:38,250 --> 00:00:39,510 They're just power of 2. 22 00:00:39,510 --> 00:00:41,370 Now, if I'm going to start on my right, 23 00:00:41,370 --> 00:00:43,170 which on your screen is going to look like the left, 24 00:00:43,170 --> 00:00:48,170 you'll see I have 2, 4, 8, 16, 32, 64, 128, 25 00:00:49,327 --> 00:00:51,360 and 256 written down. 26 00:00:51,360 --> 00:00:53,790 This tells me how many networks there are. 27 00:00:53,790 --> 00:00:56,220 This goes back to our 2 to the nth power, 28 00:00:56,220 --> 00:00:59,430 which was our formula that we used when we did this by hand. 29 00:00:59,430 --> 00:01:03,000 So if I asked you if you had a /26 network, 30 00:01:03,000 --> 00:01:06,150 how many subnets can be put into a /26 31 00:01:06,150 --> 00:01:08,850 if you were given a /24 to start with? 32 00:01:08,850 --> 00:01:10,800 Well, if I have a /24 to start with, 33 00:01:10,800 --> 00:01:12,510 I'm going to start counting up from there. 34 00:01:12,510 --> 00:01:17,510 So my first finger is going to be /25 and then /26. 35 00:01:17,530 --> 00:01:19,590 Since I asked for a /26, 36 00:01:19,590 --> 00:01:22,140 you can see the number is four. 37 00:01:22,140 --> 00:01:23,670 Now we can do it the other way 38 00:01:23,670 --> 00:01:26,160 and we can go from my left to right, 39 00:01:26,160 --> 00:01:27,060 but in your case, 40 00:01:27,060 --> 00:01:28,890 it's going to be your right side of the screen to your left, 41 00:01:28,890 --> 00:01:32,190 and this is going to tell me how many hosts or IPs I can have 42 00:01:32,190 --> 00:01:33,480 inside of a network. 43 00:01:33,480 --> 00:01:35,670 So if I start from the other side 44 00:01:35,670 --> 00:01:39,382 and I start with a /24, I have 256, 45 00:01:39,382 --> 00:01:44,382 /25, I have 128, I have a /26, that's 64, 46 00:01:44,870 --> 00:01:49,870 /27, that's 32, /28, that's 16, 47 00:01:49,874 --> 00:01:54,466 /29, that's eight, /30, that's four, 48 00:01:54,466 --> 00:01:56,970 /31, that's two. 49 00:01:56,970 --> 00:01:58,290 So you can see how this works, 50 00:01:58,290 --> 00:02:00,390 going from right to left or left to right 51 00:02:00,390 --> 00:02:02,040 be able to figure out how many networks 52 00:02:02,040 --> 00:02:03,870 or how many IPs are available. 53 00:02:03,870 --> 00:02:07,080 Now we're going to do a couple of examples using this method. 54 00:02:07,080 --> 00:02:08,910 The first one I'm going to use is this one, 55 00:02:08,910 --> 00:02:12,450 it's 192.168.0.85. 56 00:02:12,450 --> 00:02:13,980 Now, the numbers really don't matter. 57 00:02:13,980 --> 00:02:16,890 It's really what's important is that /29 at the end. 58 00:02:16,890 --> 00:02:18,390 So if you wanted to figure out 59 00:02:18,390 --> 00:02:22,350 how many subnets there were in a /29, how would you do that? 60 00:02:22,350 --> 00:02:24,960 Well, we're going to count up from right to left, 61 00:02:24,960 --> 00:02:26,700 upwards in the power of 2. 62 00:02:26,700 --> 00:02:28,440 So if I start counting on my fingers, 63 00:02:28,440 --> 00:02:33,360 I go 25, 26, 27, 28, 29. 64 00:02:33,360 --> 00:02:34,980 And what's on my 29? 65 00:02:34,980 --> 00:02:36,150 It's 32. 66 00:02:36,150 --> 00:02:40,260 There are 32 subnets if I'm using a /29 network 67 00:02:40,260 --> 00:02:42,930 within a normal Class C network. 68 00:02:42,930 --> 00:02:45,540 Now, if I'm going to look at this from an IP perspective, 69 00:02:45,540 --> 00:02:47,160 I'm going to do it the other way. 70 00:02:47,160 --> 00:02:49,320 How many IPs are there in a /29? 71 00:02:49,320 --> 00:02:51,827 Well, we're going to start with /24, 256, 72 00:02:51,827 --> 00:02:56,827 /25, 26, 27, 28, 29. 73 00:02:57,060 --> 00:02:59,670 And there you'll see I have eight IPs. 74 00:02:59,670 --> 00:03:01,800 Now, if you remember from our lessons, 75 00:03:01,800 --> 00:03:03,630 you always have a broadcast 76 00:03:03,630 --> 00:03:05,280 and you always have a network name. 77 00:03:05,280 --> 00:03:08,340 So really, I have six usable IPs for hosts. 78 00:03:08,340 --> 00:03:10,500 I have the first IP, which is my network, 79 00:03:10,500 --> 00:03:12,720 and my last IP, which is my broadcast, 80 00:03:12,720 --> 00:03:14,580 giving us a total of eight. 81 00:03:14,580 --> 00:03:17,373 Again, that's at /29, that's eight. 82 00:03:18,240 --> 00:03:23,240 The next problem we have is 192.168.1.25/28. 83 00:03:24,120 --> 00:03:28,260 So if I'm doing /28, how many subnets and how many IPs? 84 00:03:28,260 --> 00:03:30,990 Well, let's pull out our gloves again and we'll start. 85 00:03:30,990 --> 00:03:35,990 We have /25, /26, /27, /28, and the /28 has 16 on it. 86 00:03:39,600 --> 00:03:42,120 Now, if I go the other way for how many IPs, 87 00:03:42,120 --> 00:03:47,120 I'm going to go /24, /25, /26, /27, /28. 88 00:03:48,480 --> 00:03:53,480 It's also 16. So we have 16 subnets and 16 available IPs. 89 00:03:53,970 --> 00:03:56,580 You can see how this works. It makes it really easy. 90 00:03:56,580 --> 00:03:58,260 So I think you're getting the idea here, 91 00:03:58,260 --> 00:03:59,700 but let's try two more. 92 00:03:59,700 --> 00:04:01,860 This next one has a /30. 93 00:04:01,860 --> 00:04:04,440 So how many subnets and how many IPs? 94 00:04:04,440 --> 00:04:06,150 Well, let's pull out our gloves again. 95 00:04:06,150 --> 00:04:11,150 And so we have /25, /26, /27, 28, 29, and 30. 96 00:04:12,030 --> 00:04:14,250 And on 30, you see 64 97 00:04:14,250 --> 00:04:19,250 because we count it up 2, 4, 8, 16, 32, 64. 98 00:04:19,410 --> 00:04:22,800 And so by doing that, we now know we have 64 subnets. 99 00:04:22,800 --> 00:04:24,240 That's what a /30 is. 100 00:04:24,240 --> 00:04:27,030 I could take 256 IPs in a Class C 101 00:04:27,030 --> 00:04:29,700 and I could break it up 64 different times. 102 00:04:29,700 --> 00:04:31,770 Now how many IPs is that going to be? 103 00:04:31,770 --> 00:04:33,840 Well, it's 256 divided by 64, 104 00:04:33,840 --> 00:04:36,023 but if we use our gloves, we can go the other way, 105 00:04:36,023 --> 00:04:41,023 24, 25, 26, 27, 28, 29, 30, and it's four, four IPs. 106 00:04:42,780 --> 00:04:45,690 Because if we have four IPs and 64 subnets, 107 00:04:45,690 --> 00:04:48,450 that's going to give us 256 total. 108 00:04:48,450 --> 00:04:51,600 Let's try another one. This one's going to be a /31. 109 00:04:51,600 --> 00:04:54,090 Now a /31, that's not even on the table 110 00:04:54,090 --> 00:04:55,650 you told me to memorize, Jason. 111 00:04:55,650 --> 00:04:56,483 That's right. 112 00:04:56,483 --> 00:04:58,230 That's because it's a non-standard one, 113 00:04:58,230 --> 00:04:59,880 but Cisco does support it. 114 00:04:59,880 --> 00:05:02,220 It's usually used for point-to-point connections. 115 00:05:02,220 --> 00:05:04,860 So if I'm going to connect one router to another router 116 00:05:04,860 --> 00:05:06,540 and I don't need to have a network 117 00:05:06,540 --> 00:05:09,240 and a broadcast in that case with Cisco devices, 118 00:05:09,240 --> 00:05:10,920 I can use a /31. 119 00:05:10,920 --> 00:05:14,040 So I'll only use two IPs instead of the four that we had 120 00:05:14,040 --> 00:05:15,570 in the last /30 example, 121 00:05:15,570 --> 00:05:17,340 which is normally used for point-to-point. 122 00:05:17,340 --> 00:05:18,930 But again, if we pull out our hands, 123 00:05:18,930 --> 00:05:21,030 we can start going and figuring out how many subnets 124 00:05:21,030 --> 00:05:22,080 and how many IPs. 125 00:05:22,080 --> 00:05:25,493 So let's do that /25, 26, 27, 28, 29, 30, 31. 126 00:05:28,260 --> 00:05:30,150 So that tells me it's on my seventh finger. 127 00:05:30,150 --> 00:05:31,620 So if I didn't have my gloves on, 128 00:05:31,620 --> 00:05:36,287 I would just do powers of 2, 2, 4, 8, 16, 32 64, 128. 129 00:05:37,770 --> 00:05:41,880 And so that seventh finger is 128, there's 128 subnets. 130 00:05:41,880 --> 00:05:43,530 Now, I'm sure you can do the math here. 131 00:05:43,530 --> 00:05:46,320 If there's 256 total IPs in a Class C 132 00:05:46,320 --> 00:05:48,480 and we just took up 128 subnets, 133 00:05:48,480 --> 00:05:50,700 that means there's going to be two IPs per subnet. 134 00:05:50,700 --> 00:05:52,230 So let's do it with our hands anyway, 135 00:05:52,230 --> 00:05:54,300 just because that's what we're doing in this video. 136 00:05:54,300 --> 00:05:55,140 And so here we go. 137 00:05:55,140 --> 00:06:00,140 We're going to go 24, 25, 26, 27, 28, 29, 30, and 31. 138 00:06:01,200 --> 00:06:03,870 And on 31, we have a two, right? 139 00:06:03,870 --> 00:06:07,231 We can do that if we went and counted up or counted down, 140 00:06:07,231 --> 00:06:12,231 256, 128, 64, 32, 16, 8, 4, and 2. 141 00:06:13,590 --> 00:06:15,720 And that gets us to that same number of two. 142 00:06:15,720 --> 00:06:17,700 So it's all about memorizing these power of 2 143 00:06:17,700 --> 00:06:18,930 as we go through this. 144 00:06:18,930 --> 00:06:21,960 Again, a /31 is something that Cisco supported. 145 00:06:21,960 --> 00:06:24,360 Some of the other routers are starting to support it, 146 00:06:24,360 --> 00:06:27,090 but it is something that is mainly a Cisco thing. 147 00:06:27,090 --> 00:06:29,760 Let's go ahead and do one last one here, 148 00:06:29,760 --> 00:06:32,190 and this one is going to be a /32. 149 00:06:32,190 --> 00:06:34,110 So when we're doing a /32, 150 00:06:34,110 --> 00:06:36,210 you may go, "Do I even need to use my hands?" 151 00:06:36,210 --> 00:06:37,410 Well, you really don't 152 00:06:37,410 --> 00:06:40,650 because a /32 just denotes a single host. 153 00:06:40,650 --> 00:06:43,140 If I have your IP address and put /32, 154 00:06:43,140 --> 00:06:45,300 it means it's only that IP. 155 00:06:45,300 --> 00:06:47,700 And so that really is just one IP 156 00:06:47,700 --> 00:06:50,100 and there can be 256 subnets. 157 00:06:50,100 --> 00:06:52,530 But if you want to use your hands, you can do that, right? 158 00:06:52,530 --> 00:06:57,530 Because we have 25, 26, 27, 28, 29, 30, 31, and 32. 159 00:06:58,320 --> 00:07:02,520 And you see on 32, it's 256. I think you get the idea here. 160 00:07:02,520 --> 00:07:03,810 So this is how you can do this 161 00:07:03,810 --> 00:07:05,880 in a very quick and easy manner. 162 00:07:05,880 --> 00:07:07,350 Now, before we finish this video, 163 00:07:07,350 --> 00:07:09,330 I do want to put this to practice 164 00:07:09,330 --> 00:07:10,590 to some of the things you're going to see 165 00:07:10,590 --> 00:07:12,060 on the Network+ exam 166 00:07:12,060 --> 00:07:13,500 because you're likely not going to get a question 167 00:07:13,500 --> 00:07:15,663 that just says how many subnets or how many IPs. 168 00:07:15,663 --> 00:07:18,270 It's going to be a little bit more complicated than that. 169 00:07:18,270 --> 00:07:19,980 So let's go to the next question 170 00:07:19,980 --> 00:07:21,690 and you're going to be able to see what we have. 171 00:07:21,690 --> 00:07:25,250 So in this case, I have 171.129.67.160/25. 172 00:07:28,650 --> 00:07:31,710 And the question I have for you is, what's the network IP? 173 00:07:31,710 --> 00:07:32,910 What's the first host? 174 00:07:32,910 --> 00:07:35,910 What's the last host? And what's the broadcast? 175 00:07:35,910 --> 00:07:38,310 So let's pull out our gloves and take a look at this. 176 00:07:38,310 --> 00:07:39,570 So if I pull out my gloves 177 00:07:39,570 --> 00:07:43,830 and I go for the first one, a /25 is two subnets. 178 00:07:43,830 --> 00:07:45,450 Now with two subnets, 179 00:07:45,450 --> 00:07:48,510 that means if I'm using 256 IPs, 180 00:07:48,510 --> 00:07:49,980 remember I told you on the Network+ exam, 181 00:07:49,980 --> 00:07:51,840 we're always going to assume that we're doing this 182 00:07:51,840 --> 00:07:54,810 in terms of a /24 or greater 183 00:07:54,810 --> 00:07:57,000 because that's usually what you're going to see on the exam. 184 00:07:57,000 --> 00:08:01,410 So in this case, we're going to start with /24 is 256 IPs. 185 00:08:01,410 --> 00:08:05,280 Because this is a /25, I'm going to have two subnets. 186 00:08:05,280 --> 00:08:08,400 So I take that 256 and I break it in half, right? 187 00:08:08,400 --> 00:08:11,640 So if I have two subnets, what's the first subnet going to be? 188 00:08:11,640 --> 00:08:13,830 Well, it's going to start .0. 189 00:08:13,830 --> 00:08:15,810 What's the second subnet going to be? 190 00:08:15,810 --> 00:08:19,500 It's going to start at 128 because we have 128 IPs. 191 00:08:19,500 --> 00:08:23,160 So the first one goes from 0 to 127, 192 00:08:23,160 --> 00:08:26,760 and the second one is going to go from 128 to 255, 193 00:08:26,760 --> 00:08:28,710 which gives us our network ID. 194 00:08:28,710 --> 00:08:31,223 Our network ID is 171.129.67.128, 195 00:08:34,110 --> 00:08:37,799 and our broadcast ID is going to be .255. 196 00:08:37,799 --> 00:08:40,559 So what's our first host and our last host? 197 00:08:40,559 --> 00:08:42,929 Well, it's going to be .129, 198 00:08:42,929 --> 00:08:45,270 and our last host is going to be .254 199 00:08:45,270 --> 00:08:47,250 because our first host is always one above 200 00:08:47,250 --> 00:08:48,390 what the network was, 201 00:08:48,390 --> 00:08:50,190 and our last host is always one below 202 00:08:50,190 --> 00:08:51,750 what the broadcast was. 203 00:08:51,750 --> 00:08:53,400 That's how this works when you're just doing it 204 00:08:53,400 --> 00:08:55,920 with your hands, it makes it very quick and easy. 205 00:08:55,920 --> 00:08:57,240 Let's try another one. 206 00:08:57,240 --> 00:09:00,567 The next one we have is 56.187.210.21/28. 207 00:09:03,270 --> 00:09:05,430 So if I want to take a /28, 208 00:09:05,430 --> 00:09:08,190 we want to ask how many subnets and how many IP addresses 209 00:09:08,190 --> 00:09:09,810 'cause that's going to help us write down 210 00:09:09,810 --> 00:09:11,700 where our network and broadcasts are, 211 00:09:11,700 --> 00:09:13,350 and that helps us figure out our first hosts 212 00:09:13,350 --> 00:09:14,430 and our last host. 213 00:09:14,430 --> 00:09:16,710 So if we have a /28, we'll pull out our gloves 214 00:09:16,710 --> 00:09:19,617 and we'll go 25, 26, 27, 28, 215 00:09:19,617 --> 00:09:22,680 and 28 is my pinky, which is a 16. 216 00:09:22,680 --> 00:09:25,230 So there are 16 subnets. 217 00:09:25,230 --> 00:09:28,200 Now if I go the other way, how many IPs are there? 218 00:09:28,200 --> 00:09:31,830 Well, 24, 25, 26, 27, 28. 219 00:09:31,830 --> 00:09:36,830 There's also 16 IPs. So 16 IPs and 16 subnets. 220 00:09:37,290 --> 00:09:38,880 Now if you take those 16 IPs, 221 00:09:38,880 --> 00:09:42,330 you're going to go 0 through 15, that's the first range, 222 00:09:42,330 --> 00:09:45,450 16 through 31, that's the second range. 223 00:09:45,450 --> 00:09:47,160 If we look at our IP address we were given, 224 00:09:47,160 --> 00:09:49,230 it ended in .21. 225 00:09:49,230 --> 00:09:50,400 Where does that fall? 226 00:09:50,400 --> 00:09:54,060 Well, it falls in that second range, from 16 to 31. 227 00:09:54,060 --> 00:09:58,590 So our network is 56.187.210.16, 228 00:09:58,590 --> 00:10:02,910 our broadcast is 56.187.210.31, 229 00:10:02,910 --> 00:10:04,500 and then we take our last host, 230 00:10:04,500 --> 00:10:06,990 which is one less than the broadcast, .30, 231 00:10:06,990 --> 00:10:10,800 and our first host, one more than the network, .17. 232 00:10:10,800 --> 00:10:14,010 That's how we can do this all just using our hands 233 00:10:14,010 --> 00:10:15,420 with no pen and paper, 234 00:10:15,420 --> 00:10:18,990 we can get these answers very quickly as we go through. 235 00:10:18,990 --> 00:10:21,270 I hope this subnetting by hand was helpful. 236 00:10:21,270 --> 00:10:22,770 And if you didn't get the first time, 237 00:10:22,770 --> 00:10:24,720 go ahead and rewatch the video again 238 00:10:24,720 --> 00:10:26,010 'cause once it clicks, 239 00:10:26,010 --> 00:10:29,040 it makes all of your subnetting problems so easy 240 00:10:29,040 --> 00:10:30,420 and so quick to get through 241 00:10:30,420 --> 00:10:32,913 and you'll have no issues on the Network+ exam.