WEBVTT 00:00.750 --> 00:10.200 Well, here it is, a quick crash course review in IP addressing topics that it is assumed knowledge 00:10.500 --> 00:20.790 for someone like you who's going to be a pen tester or a cybersecurity analysts or just a any kind of 00:20.790 --> 00:23.700 cyber and security combination. 00:24.030 --> 00:30.450 So IP addressing is just stuff we have to know backwards, forwards, inside and out. 00:30.930 --> 00:41.760 And remember, it all comes down to binary where we have eight bits and an IPV four address has 32 of 00:41.760 --> 00:45.840 these bits and it has a 32 bit subnet mask. 00:46.080 --> 00:54.540 And those bits are used in combination to determine if you're on the same network with another node. 00:54.870 --> 01:01.140 So I will walk you through the calculations. 01:01.140 --> 01:04.170 And just again, a real crash course. 01:04.530 --> 01:07.710 But if you don't know this stuff, now is the time. 01:07.710 --> 01:12.780 You absolutely have to learn this stuff backwards, forwards, inside and out. 01:13.230 --> 01:18.510 So if you don't have access to curriculum, you'd want to start turning to something like YouTube for 01:18.510 --> 01:21.360 sure, and you'd want to start watching. 01:21.750 --> 01:28.500 I don't even have to search an IP address ENG or IP subnet NG or any of these topics in YouTube to know 01:28.680 --> 01:32.610 there's going to be thousands of videos on the subject there. 01:32.850 --> 01:39.690 You have to learn this stuff, get this stuff, learn if any of this review is foreign to you. 01:40.230 --> 01:50.370 Now, what I always do, any time I'm asked to do anything involving subheading or IP address calculations 01:50.370 --> 01:55.170 or anything like that, I always will make on my scratch paper. 01:55.440 --> 02:00.240 And you're always have some kind of note taking capability when you're in an exam. 02:00.480 --> 02:04.200 I will make a conversion chart that looks just like this. 02:04.560 --> 02:14.640 It is the values of the binary bit positions and it's to raise to the seventh equals 128 and notice 02:14.640 --> 02:17.120 it goes to raised to the zero is one. 02:17.130 --> 02:20.700 This table is so incredibly easy to complete. 02:21.480 --> 02:28.050 So, you know, we just know that two raised to the zero is the value of one because anything raised 02:28.050 --> 02:31.230 to the value of zero is equal to one. 02:31.650 --> 02:33.970 And once you know that, you just double it. 02:33.990 --> 02:41.700 One, two, four, eight, 16, 32, 64 and one take the appropriate to raise to the whatever values 02:41.700 --> 02:44.970 are in the first layer there or table row. 02:45.000 --> 02:45.440 That's it. 02:45.450 --> 02:45.980 That's it. 02:45.990 --> 02:46.680 It's a row. 02:46.980 --> 02:53.970 The first row of my conversion chart notice is those two raised to the whatever values and those come 02:53.970 --> 02:59.850 in handy later on when we're actually doing sub netting, for example. 03:00.510 --> 03:11.850 So the conversion chart in action, that binary address that we saw earlier, that 11001101 address, 03:12.300 --> 03:20.860 well that would convert to in decimal 128 plus 64 plus eight plus four plus one. 03:21.150 --> 03:23.190 Let me pause the video and do that math. 03:24.000 --> 03:27.990 Well, I think the answer is 205. 03:27.990 --> 03:29.400 And let me make sure that. 03:29.400 --> 03:29.810 Right. 03:29.820 --> 03:31.800 Let me grab the calculator. 03:32.070 --> 03:39.930 And if I go to the calculator, oh, in fact, we can even set it to scientific or programmer. 03:40.230 --> 03:51.960 And if I send it to programmer and say that I want to enter this in binary, so I say 110011. 03:52.940 --> 03:54.710 And then zero one. 03:56.150 --> 03:59.540 And notice we see it in decimal 205. 03:59.780 --> 04:00.720 So that's great. 04:00.740 --> 04:02.780 I just confirmed that my. 04:03.230 --> 04:07.340 I'll lower that calculator and keep it on our taskbar. 04:07.490 --> 04:12.320 We may need it again, but there's the proof of my manual addition. 04:12.590 --> 04:17.450 128 plus 64 plus eight plus four plus one does indeed. 04:17.530 --> 04:19.760 Two's equal, 205. 04:19.970 --> 04:23.300 And that's the decimal value of that octet. 04:23.660 --> 04:28.190 Now, what if we were asked, what is 212 in binary? 04:28.400 --> 04:34.010 Well, now we have to play a little subtraction game and that goes basically like this. 04:34.760 --> 04:40.970 Can we take 128 from 212 and not go into the negative? 04:41.270 --> 04:43.820 And the answer to that is, yes, we can. 04:44.120 --> 04:46.040 So we go ahead and do that. 04:46.040 --> 04:52.700 Subtraction 212, 128, rather, from 212. 04:53.030 --> 04:53.570 All right. 04:53.570 --> 04:54.560 Let me do this. 04:54.590 --> 04:56.390 Gosh, I'm doing this on paper. 04:56.400 --> 04:57.260 You can't see it. 04:57.260 --> 04:59.960 I know this is making for exciting television, isn't it? 05:00.320 --> 05:02.660 But let me just try and do this real quick. 05:05.330 --> 05:12.970 So we have oh my gosh, I suck at basic arithmetic. 05:12.980 --> 05:16.490 Now let me grab the calculator and just cheat. 05:17.000 --> 05:18.410 But you see what I'm doing, right? 05:18.410 --> 05:27.670 You're doing a big subtraction problem and you're getting it to where the remainder is going to be zero. 05:27.980 --> 05:30.260 So let me go with the standard calculator mode. 05:30.260 --> 05:31.640 We don't need to get fancy here. 05:31.850 --> 05:33.980 So we have 212. 05:34.220 --> 05:36.920 Can we subtract 128 from that? 05:36.920 --> 05:38.210 Yes, we can. 05:38.300 --> 05:39.740 And what's the remainder? 05:39.860 --> 05:40.910 It's 84. 05:41.210 --> 05:41.600 Okay. 05:41.600 --> 05:47.360 So we have a one turned on the one bit position in the two raised to the seventh. 05:47.690 --> 05:50.180 So now to raise to the six is 64. 05:50.180 --> 05:54.710 If we subtract that, we get 20. 05:55.040 --> 05:58.580 So we have a one in the position of 128. 05:58.580 --> 06:01.100 We have a one in the position of 64. 06:01.370 --> 06:02.930 We have 20 left over. 06:02.930 --> 06:09.350 We cannot subtract 32 from 20, but we can subtract 16 from 20. 06:09.710 --> 06:13.340 If I subtract 16 from 20, it gives us the remainder of four. 06:13.340 --> 06:22.550 So we have as one in the 16 position, we have a zero in the eight position, we have a one in the four 06:22.550 --> 06:27.710 position and then we have a zero in the two position and a zero in the one position. 06:28.010 --> 06:36.740 So the 212 in binary works out to 11010100. 06:36.920 --> 06:38.210 Can we test that? 06:38.390 --> 06:39.290 We sure can. 06:39.530 --> 06:44.360 So I grabbed the scientific calculator, or I can grab the programmer calculator. 06:44.360 --> 06:45.050 It's easier. 06:45.350 --> 06:48.500 And I will say I want to enter in binary 06:48.800 --> 06:55.520 11010100 06:55.760 --> 06:58.580 and that gives us 212. 06:58.820 --> 07:01.040 So we just checked our math there. 07:01.280 --> 07:02.750 That is great. 07:03.200 --> 07:09.430 So we can now look at an IP address in a whole different way. 07:09.430 --> 07:19.790 Gateway We know that 1921681 100 equates to the underlying binary, and we could even calculate what 07:19.790 --> 07:22.340 that underlying binary is. 07:22.880 --> 07:24.620 And that is pretty cool. 07:24.800 --> 07:26.660 And we could go the other direction as well. 07:27.290 --> 07:34.580 Now, subnet masks, remember, there's default subnet masks for the original address classes that were 07:34.580 --> 07:35.240 defined. 07:35.780 --> 07:41.660 They had originally said, okay, let's make a default mask for Class A in two, five, five and then 07:41.660 --> 07:42.740 000. 07:42.740 --> 07:44.390 That's eight bits. 07:44.390 --> 07:49.130 Notice the prefix notation, eight bits of masking. 07:49.670 --> 07:59.750 If we do 255255, that's 16 bits of masking and 24 bits of masking with that 2552552550. 08:00.350 --> 08:01.940 So here's the thing. 08:02.390 --> 08:12.440 As we extend the size of the subnet mask, we reduce the number of nodes we can support per network. 08:12.590 --> 08:16.910 So that's the big balancing act that you're playing with subnet masks. 08:17.240 --> 08:24.320 The more bits you have to use to identify the network, the less bits you have left over to identify 08:24.410 --> 08:25.040 hosts. 08:26.410 --> 08:34.060 So now let's check out an example of an IP address and a subnet mask and let's figure out the prefix 08:34.060 --> 08:35.980 notation for that mask. 08:36.460 --> 08:40.540 So here we can see 255255255, 224. 08:40.630 --> 08:49.240 So we have eight bits of on bits in the first octet and then we have eight bits of on bits in the next 08:49.240 --> 08:49.680 octet. 08:49.690 --> 08:53.830 Then we have eight bits of on bits in the third octet. 08:54.160 --> 08:57.940 So that's eight plus eight plus eight, that's 24 bits. 08:58.120 --> 09:03.010 But then to 24, how many bits are on for the two. 09:03.010 --> 09:03.730 24. 09:03.820 --> 09:09.970 Well it sure looks like three bits are being utilised there to give us that number 224. 09:10.180 --> 09:13.480 And in fact, that makes sense from our table, doesn't it? 09:13.840 --> 09:25.060 The two raised to the seventh was 128, the two raised to the sixth was the 64 and the two raised to 09:25.060 --> 09:27.880 the fifth was the 32. 09:28.060 --> 09:32.650 If you add 128 plus 64 plus 32, I do believe. 09:32.650 --> 09:34.300 Let me do that on my scratch paper. 09:34.540 --> 09:37.990 128 plus 64 plus 32. 09:38.650 --> 09:47.110 That is 14 carry the one that is nine and then 12 carry the 1 to 24. 09:47.350 --> 09:50.200 So 128, 64 and 32. 09:50.380 --> 09:53.290 Those three bits give us the 224 value. 09:53.500 --> 09:56.650 This is a slash 27 mask. 09:58.430 --> 10:01.440 Now if you are brand new to something like this. 10:02.480 --> 10:06.110 First of all, you do have your work cut out for you. 10:06.140 --> 10:08.840 You definitely want to go and study this intently. 10:08.840 --> 10:13.010 But just to let you know, you're always going to have a way to check your work. 10:13.370 --> 10:13.710 Right. 10:13.730 --> 10:15.600 So that's what's great about this. 10:15.610 --> 10:25.790 So we were just looking in the example where we had an IP address and then we had the 255255 224 in 10:25.790 --> 10:26.840 the last octet. 10:27.080 --> 10:32.750 And I said that it was a slash 27 mask that would result. 10:32.990 --> 10:40.790 And notice we can go ahead and confirm that with any good old IP subnet calculator that we might find 10:40.790 --> 10:42.560 floating around the interweb. 10:43.540 --> 10:49.000 Now again, remember, this is a fast paced review of this material. 10:49.210 --> 10:55.100 If this is something you need to go back and study, that is just fine. 10:55.120 --> 10:57.100 Don't be ashamed by any of this. 10:57.100 --> 11:01.390 That may be foggy or fuzzy and you need to go back and you need to learn this stuff. 11:01.870 --> 11:04.100 Let's talk more about those address classes. 11:04.120 --> 11:12.130 So what they did to create the address classes was they just forced the initial bit settings. 11:12.340 --> 11:18.100 So they said the initial bit setting of the address, the IP address itself, forget the subnet mask. 11:18.100 --> 11:20.300 Now we're talking about the IP address itself. 11:20.920 --> 11:27.850 If it's forced to a zero at the very first octet, well then this will make for the address classes 11:27.880 --> 11:32.690 of class AA, which is 1 to 127. 11:33.100 --> 11:36.280 127 is actually unusable. 11:36.280 --> 11:38.500 They reserved that for loopback purposes. 11:38.830 --> 11:41.290 So it's really 1 to 126. 11:41.890 --> 11:47.200 Then they did the class B, it's forced to the one zero high order bit setting. 11:47.200 --> 11:54.790 And this gives us addresses numbered 128 to 191 in the first octet, class C was a high order bit setting 11:54.790 --> 12:02.290 of 110, which gave us 192 to 223 and class d1110 224 two 239. 12:02.800 --> 12:04.570 What is the Class D for? 12:04.930 --> 12:09.340 Why don't you see those on your IP address primary? 12:09.340 --> 12:10.720 You know, Nic often. 12:10.720 --> 12:16.660 Well, it's because those are for multicast addressing and multicast addresses. 12:16.900 --> 12:20.920 They are going to be assigned to your network interface card. 12:21.130 --> 12:29.410 But when some application most likely is subscribing to receive a multicast feed, then it will dynamically 12:29.410 --> 12:32.800 start listening on one of those multicast IP addresses. 12:33.040 --> 12:37.270 So multicast a very interesting area of IP. 12:38.260 --> 12:38.770 All right. 12:38.770 --> 12:40.630 So how about some netting? 12:40.870 --> 12:42.880 Well, take a look at this scenario. 12:43.180 --> 12:46.780 We have the ten .0.0.0 network. 12:46.900 --> 12:55.480 It would normally have the Class a/8, but we do four bits of sub netting, so we end up having a slash 12:55.480 --> 13:01.480 12 and that equates to 255 to 40 zero zero for the subnet mask. 13:02.080 --> 13:09.850 What this means is if we're using two bits for some netting, well then the four bits that we're using 13:09.850 --> 13:14.890 for subletting plugs into our formula as to raise to the four. 13:14.890 --> 13:18.490 And that's going to give us 16 subnets that we could work with. 13:19.150 --> 13:27.070 Now if we are using 16 ah excuse me, if we are using four bits for sub netting. 13:27.130 --> 13:27.520 Right. 13:28.000 --> 13:36.040 So we're using the four bits of sub netting plus the eight bits in the first octet for that subnet mask. 13:36.280 --> 13:46.720 So we're using the 12 bits total for the network addressing well if there's 32 bits in the address and 13:46.720 --> 13:55.090 we're using 12 of those for identifying the network, then that's going to leave 20 bits for host addressing 13:55.570 --> 14:06.310 plugging 20 into our formula of two raised to the X, we get over a million hosts per subnet. 14:06.640 --> 14:07.930 Isn't that amazing? 14:07.930 --> 14:10.390 And you need a calculator to figure out that number. 14:10.660 --> 14:14.200 Notice the minus two when you're calculating the hosts per subnet. 14:14.530 --> 14:21.040 That's because no host can have an all zeros or an all one's host address. 14:21.310 --> 14:25.900 Those are reserved for network ID and the broadcast on that subnet. 14:26.380 --> 14:28.000 So interesting there. 14:28.000 --> 14:31.030 We'd need a calculator to figure out the host for subnet. 14:31.780 --> 14:33.880 What would the subnets look like. 14:33.880 --> 14:37.750 Will they would increment on that number 16. 14:37.990 --> 14:38.440 Yeah. 14:38.860 --> 14:45.160 So we saw that the 16 subnets that we could create. 14:45.160 --> 14:45.530 Yeah. 14:45.550 --> 14:49.660 They increment on that number 16, it's what we call the block size. 14:49.930 --> 14:56.320 So you'd have ten 000 1016 zero zero 1030 200. 14:56.380 --> 14:56.710 Yeah. 14:56.710 --> 14:59.380 And that would be your subnets. 14:59.950 --> 15:00.790 So cool. 15:01.830 --> 15:09.780 Now there is another type of sub netting question that we should be able to answer pretty easily, and 15:09.780 --> 15:17.310 that is if we have 1921681024 and we need to create six subnets. 15:17.670 --> 15:24.270 Well, if we steal or borrow three bits, we can create eight additional subnets. 15:24.360 --> 15:25.800 That's two to the three. 15:26.040 --> 15:27.750 If we're borrowing the three bits. 15:28.170 --> 15:30.960 So if they needed six, we can give them eight. 15:31.410 --> 15:32.050 That's great. 15:32.070 --> 15:33.810 They'll have more than they need. 15:33.930 --> 15:38.910 And notice the subnets are going to be shown below there. 15:39.060 --> 15:47.460 We're going to borrow the three bits, so we'll have the slash 27 mask and then we'll be incrementing 15:47.460 --> 15:58.060 here on 32 because we go three bits deep in to our conversion chart and we have a block size of 32. 15:58.320 --> 16:05.370 So it's zero 32, 64, 96, one, 28, 160, and there would be eight of these. 16:05.550 --> 16:08.640 But I just bothered to list the six that they need. 16:09.000 --> 16:16.200 But notice there would be two additional subnets that, hey, we may need in the future. 16:16.950 --> 16:20.850 So these are the types of examples. 16:20.850 --> 16:27.660 These are the types of things you need to know about IP addresses backwards, forwards, inside and 16:27.660 --> 16:28.140 out. 16:28.530 --> 16:33.930 And again, this is a very fast paced review of what you need to know. 16:34.230 --> 16:40.080 You can certainly chat with me if you are struggling to find additional education in this area. 16:40.090 --> 16:46.560 But like I said, it's all over the place because all aspects of information technology folks should 16:46.560 --> 16:47.460 really know this. 16:48.390 --> 16:53.130 By the way, let's think about public versus private for a moment. 16:53.550 --> 17:01.690 So we have all of these private devices, as you can see here, with their private addressing of 192168. 17:01.710 --> 17:02.340 That's great. 17:02.670 --> 17:10.890 But we do need a public IP address still and we know that network address translation is what will allow 17:10.890 --> 17:17.850 all these devices to have their addresses translated into the public IP for communication on the public 17:17.850 --> 17:18.300 internet. 17:18.600 --> 17:25.650 So one of the big things that you also should have committed to memory is what are those private address 17:25.650 --> 17:26.280 spaces? 17:26.550 --> 17:34.230 What are those IPv4 address spaces that cannot communicate by themselves on the public Internet that 17:34.230 --> 17:35.760 need translation? 17:36.240 --> 17:41.070 There's three classes of them defined in the famous requests for comment. 17:41.100 --> 17:42.000 1918. 17:42.450 --> 17:48.150 So requests for comments 1918 is something else that I have memorized the title for sure. 17:48.480 --> 17:51.150 And they reserved all of the ten slash eight. 17:51.750 --> 17:55.440 They reserved the one 7216 slash 12. 17:55.560 --> 18:00.870 That gives us one 7216 to 172, 31 to 50 5 to 55. 18:01.170 --> 18:02.800 And they reserved the 192. 18:02.820 --> 18:09.900 168 slash 16, which gives us 1921682192168255255. 18:10.530 --> 18:18.000 Now, what you often see in practice is that for large corporations they'll use the tender space because 18:18.000 --> 18:21.270 they want a ton of address space in their corporation. 18:21.690 --> 18:26.670 Medium sized companies tend to use one 7216, and you've seen it plenty of times. 18:26.820 --> 18:30.330 When do ISP's set up their little home routers to do? 18:30.570 --> 18:30.860 Yeah. 18:30.900 --> 18:39.450 Disseminate the smallest address spaces the 1921681 or the 1921680 or the 192168 ten. 18:39.750 --> 18:44.850 So they'll use that class C address space for the private addressing. 18:45.570 --> 18:47.460 Well, I hope you enjoyed that. 18:47.760 --> 18:52.770 Just blazingly fast kind of review of key IP addressing concepts. 18:53.040 --> 19:00.480 Again, make sure that you understand IP addressing backwards, forwards, inside and out.