1 1 00:00:00,302 --> 00:00:03,340 If you think back to our lesson on IP addressing, 2 2 00:00:03,340 --> 00:00:04,357 specifically with version four, 3 3 00:00:04,357 --> 00:00:06,889 we talked about the fact, that IPv4 4 4 00:00:06,889 --> 00:00:08,755 was running out of IP addresses, 5 5 00:00:08,755 --> 00:00:11,058 and this was becoming a huge problem. 6 6 00:00:11,058 --> 00:00:14,466 Now, IPV six, honestly, wasn't ready yet to be developed. 7 7 00:00:14,466 --> 00:00:16,201 And they were still in the process of it. 8 8 00:00:16,201 --> 00:00:18,105 And so, something else had to come up, 9 9 00:00:18,105 --> 00:00:19,535 to help us with this problem. 10 10 00:00:19,535 --> 00:00:21,727 And that is what address translation did. 11 11 00:00:21,727 --> 00:00:24,730 It was there, to help solve this problem for us. 12 12 00:00:24,730 --> 00:00:26,453 And there was two versions of this, 13 13 00:00:26,453 --> 00:00:29,728 Network Address Translation and Port Address Translation. 14 14 00:00:29,728 --> 00:00:32,500 Now, Network Address Translation is a way for us, 15 15 00:00:32,500 --> 00:00:35,015 to conserve those limited number of IPv4 addresses. 16 16 00:00:35,015 --> 00:00:37,991 For example, if I go to your house right now, 17 17 00:00:37,991 --> 00:00:39,906 how many devices do you have on your network? 18 18 00:00:39,906 --> 00:00:42,040 You might have five or ten or fifteen. 19 19 00:00:42,040 --> 00:00:45,490 In my house, we each have a smartphone, a tablet, 20 20 00:00:45,490 --> 00:00:48,087 a laptop, a desktop, some video game machines, 21 21 00:00:48,087 --> 00:00:49,620 and there's four of us. 22 22 00:00:49,620 --> 00:00:51,550 So right there, we've got twelve, fifteen, 23 23 00:00:51,550 --> 00:00:53,070 twenty devices, right? 24 24 00:00:53,070 --> 00:00:54,520 Now, if you start adding things up, 25 25 00:00:54,520 --> 00:00:57,670 like, smart thermostats, and file servers and desktops, 26 26 00:00:57,670 --> 00:01:00,470 we quickly get to twenty or thirty or forty devices 27 27 00:01:00,470 --> 00:01:02,110 in any single house. 28 28 00:01:02,110 --> 00:01:05,255 But, in each house, we only have one public IP addresses. 29 29 00:01:05,255 --> 00:01:08,349 So, how do all these devices get onto the internet? 30 30 00:01:08,349 --> 00:01:12,086 Well, that is where NAT and PAT come into play. 31 31 00:01:12,086 --> 00:01:14,753 Now, NAT or Network Address Translation is going 32 32 00:01:14,753 --> 00:01:17,222 to allow you to translate your private IP address 33 33 00:01:17,222 --> 00:01:18,912 into a public IP address, 34 34 00:01:18,912 --> 00:01:21,424 for routing over the public networks, like the internet. 35 35 00:01:21,424 --> 00:01:24,610 Now, there's another variation out there known as PAT, 36 36 00:01:24,610 --> 00:01:25,447 which is Port Address Translation. 37 37 00:01:25,447 --> 00:01:27,370 And we're going to talk about that 38 38 00:01:27,370 --> 00:01:28,507 at the end of this video too. 39 39 00:01:28,507 --> 00:01:30,450 Now, when we talk about different types 40 40 00:01:30,450 --> 00:01:33,590 of address translation, there are three main ones out there. 41 41 00:01:33,590 --> 00:01:36,140 There is DNAT, SNAT and PAT. 42 42 00:01:36,140 --> 00:01:38,602 let's take each one, one at a time. 43 43 00:01:38,602 --> 00:01:40,410 Let's start out with DNAT, 44 44 00:01:40,410 --> 00:01:42,470 or Dynamic Network Address Translation. 45 45 00:01:42,470 --> 00:01:45,680 Now, Dynamic NAT (DNAT) is going to take an IP address, 46 46 00:01:45,680 --> 00:01:47,686 and automatically assign it from a pool of IP addresses, 47 47 00:01:47,686 --> 00:01:50,426 and give us a one-to-one translation. 48 48 00:01:50,426 --> 00:01:53,242 Now, why would we want to use Dynamic NAT (DNAT)? 49 49 00:01:53,242 --> 00:01:55,630 Well, if you remember, I talked about the fact, 50 50 00:01:55,630 --> 00:01:57,505 that public IP addresses cost money. 51 51 00:01:57,505 --> 00:01:59,290 Maybe, you only wanted to pay 52 52 00:01:59,290 --> 00:02:00,970 for five addresses in your business, 53 53 00:02:00,970 --> 00:02:02,722 but you have thirty workstations there. 54 54 00:02:02,722 --> 00:02:05,770 Well, in the old days, only 20% of your people 55 55 00:02:05,770 --> 00:02:07,270 were going online at any time, 56 56 00:02:07,270 --> 00:02:09,582 and so, Dynamic NAT (DNAT) worked out really well for that. 57 57 00:02:09,582 --> 00:02:11,700 The way dynamic NAT would work, 58 58 00:02:11,700 --> 00:02:13,060 is when you want to get online, 59 59 00:02:13,060 --> 00:02:14,680 your computer, would go to the router, 60 60 00:02:14,680 --> 00:02:16,640 it would borrow one of these five IP addresses, 61 61 00:02:16,640 --> 00:02:18,836 it would do a translation from your private IP 62 62 00:02:18,836 --> 00:02:21,977 to your public IP and that way you'd be able to use it. 63 63 00:02:21,977 --> 00:02:24,598 Go online, make the request and then when you're done, 64 64 00:02:24,598 --> 00:02:26,980 your computer turned that public IP, 65 65 00:02:26,980 --> 00:02:29,019 back into the router, back to the shared pool. 66 66 00:02:29,019 --> 00:02:32,340 This way you can maximize your public IP space 67 67 00:02:32,340 --> 00:02:34,290 for the most amount of internal clients. 68 68 00:02:34,290 --> 00:02:36,570 And it did all of this dynamically and you didn't have to 69 69 00:02:36,570 --> 00:02:37,680 worry about it. 70 70 00:02:37,680 --> 00:02:40,065 Just like it does with DHCP, to give you internal addresses, 71 71 00:02:40,065 --> 00:02:43,180 this was all done, from a matching of an internal scope 72 72 00:02:43,180 --> 00:02:44,022 to an external scope. 73 73 00:02:44,022 --> 00:02:46,036 And so, in just a quick microsecond, 74 74 00:02:46,036 --> 00:02:48,448 you could then take this address, make the request, 75 75 00:02:48,448 --> 00:02:49,690 and then give it back. 76 76 00:02:49,690 --> 00:02:52,330 Now, if you want to think about this, like a family, 77 77 00:02:52,330 --> 00:02:54,329 let's say you have a mom and a dad, 78 78 00:02:54,329 --> 00:02:56,310 and two teenagers living in the house, 79 79 00:02:56,310 --> 00:02:57,830 but you only have two cars. 80 80 00:02:57,830 --> 00:02:59,250 Well, if somebody wants to go the mall, 81 81 00:02:59,250 --> 00:03:02,490 they would grab the car keys, get in the car, drive out, 82 82 00:03:02,490 --> 00:03:04,040 and then when they're done, they'd bring the car back 83 83 00:03:04,040 --> 00:03:05,200 and put the keys back up, 84 84 00:03:05,200 --> 00:03:06,450 and then somebody else can grab the keys 85 85 00:03:06,450 --> 00:03:07,490 and take out the car. 86 86 00:03:07,490 --> 00:03:09,081 That's the way Dynamic NAT (DNAT) worked. 87 87 00:03:09,081 --> 00:03:11,977 Now, when we're dealing with Static NAT or (SNAT), 88 88 00:03:11,977 --> 00:03:13,767 this was a static assignment, 89 89 00:03:13,767 --> 00:03:17,097 where I would manually assign a private IP to a public IP 90 90 00:03:17,097 --> 00:03:19,405 and each time it was a one-to-one translation. 91 91 00:03:19,405 --> 00:03:22,153 So, in this case, if I had five public IP addresses, 92 92 00:03:22,153 --> 00:03:24,504 I would also have five private ones, 93 93 00:03:24,504 --> 00:03:26,270 and I couldn't multi share them 94 94 00:03:26,270 --> 00:03:27,607 the way I could with Dynamic NAT (DNAT). 95 95 00:03:27,607 --> 00:03:29,480 So, in this case, I have to have one car 96 96 00:03:29,480 --> 00:03:30,520 for every person, right? 97 97 00:03:30,520 --> 00:03:33,090 Somebody has to physically do all that assignment as well, 98 98 00:03:33,090 --> 00:03:34,158 because it's done statically. 99 99 00:03:34,158 --> 00:03:36,950 Now, why would somebody want to use Static NAT (SNAT)? 100 100 00:03:36,950 --> 00:03:37,783 You may be wondering, 101 101 00:03:37,783 --> 00:03:39,530 cause it seems kind of like a silly way to do it, 102 102 00:03:39,530 --> 00:03:40,815 when Dynamic NAT (DNAT) was available. 103 103 00:03:40,815 --> 00:03:42,840 Well, Static NAT (SNAT) was really used 104 104 00:03:42,840 --> 00:03:44,360 just as a security feature. 105 105 00:03:44,360 --> 00:03:45,903 It was a way to have all those public IP's, 106 106 00:03:45,903 --> 00:03:48,703 not shown, exactly which client was attached 107 107 00:03:48,703 --> 00:03:50,431 to each one, to the outside world. 108 108 00:03:50,431 --> 00:03:52,186 And so, it added a little bit of a smoke screen, 109 109 00:03:52,186 --> 00:03:54,174 if you will, that kind of hid those devices 110 110 00:03:54,174 --> 00:03:55,330 behind the router. 111 111 00:03:55,330 --> 00:03:58,010 Now, the third way, and the most common one 112 112 00:03:58,010 --> 00:03:59,520 that we use today is what's known as 113 113 00:03:59,520 --> 00:04:01,199 PAT or Port Address Translation. 114 114 00:04:01,199 --> 00:04:03,330 In fact, as you're watching this video, 115 115 00:04:03,330 --> 00:04:06,095 you're probably using PAT on your home network right now, 116 116 00:04:06,095 --> 00:04:08,120 without even knowing it. 117 117 00:04:08,120 --> 00:04:10,570 Now, this is what happens when you have multiple private 118 118 00:04:10,570 --> 00:04:13,261 IP addresses, sharing only one public address. 119 119 00:04:13,261 --> 00:04:15,341 Now, again, my house, we have fifteen 120 120 00:04:15,341 --> 00:04:16,765 or twenty different network devices, 121 121 00:04:16,765 --> 00:04:19,278 but, we only have one public IP. 122 122 00:04:19,278 --> 00:04:21,850 Now, the problem is all of us want 123 123 00:04:21,850 --> 00:04:23,238 to get online at the same time, right? 124 124 00:04:23,238 --> 00:04:25,032 We don't want to have to share that one IP. 125 125 00:04:25,032 --> 00:04:27,635 Well, by using PAT, we can do that, 126 126 00:04:27,635 --> 00:04:30,141 because it allows a many-to-one translation, 127 127 00:04:30,141 --> 00:04:32,730 instead of the one-to-one, the Dynamic NAT (DNAT) 128 128 00:04:32,730 --> 00:04:34,540 and Static NAT (SNAT) required. 129 129 00:04:34,540 --> 00:04:35,870 Now, this is a great thing, 130 130 00:04:35,870 --> 00:04:37,688 because it allows me to take these small networks, 131 131 00:04:37,688 --> 00:04:41,180 like small offices, and home offices and small businesses, 132 132 00:04:41,180 --> 00:04:43,405 and be able to connect them through one IP, 133 133 00:04:43,405 --> 00:04:44,819 out to the internet. 134 134 00:04:44,819 --> 00:04:46,700 Now, I'm going to show you how this works 135 135 00:04:46,700 --> 00:04:48,264 by using a diagram, in just a second, so bear with me. 136 136 00:04:48,264 --> 00:04:50,810 Now, before we do that though, 137 137 00:04:50,810 --> 00:04:52,510 I want to talk about the different names 138 138 00:04:52,510 --> 00:04:54,066 of the NAT IP addresses. 139 139 00:04:54,066 --> 00:04:56,230 They have specific names that you have to memorize 140 140 00:04:56,230 --> 00:04:57,330 for the exam. 141 141 00:04:57,330 --> 00:04:59,760 There's the Inside local, Inside global, 142 142 00:04:59,760 --> 00:05:01,411 Outside local and Outside global. 143 143 00:05:01,411 --> 00:05:04,347 For your inside local, this is your private IP address 144 144 00:05:04,347 --> 00:05:06,440 that references an inside device. 145 145 00:05:06,440 --> 00:05:09,543 For your inside global, this is your public IP address 146 146 00:05:09,543 --> 00:05:12,300 or your global one that's being referenced 147 147 00:05:12,300 --> 00:05:13,630 for an inside device. 148 148 00:05:13,630 --> 00:05:15,592 For your outside local, this is your private IP address, 149 149 00:05:15,592 --> 00:05:17,947 that's being referenced from the outside 150 150 00:05:17,947 --> 00:05:19,928 and you have your global device 151 151 00:05:19,928 --> 00:05:23,150 or your outside global is coming to be a public IP address, 152 152 00:05:23,150 --> 00:05:25,046 referencing that outside device. 153 153 00:05:25,046 --> 00:05:27,850 Now again, anytime you see the word global, 154 154 00:05:27,850 --> 00:05:29,630 I want you to think about public. 155 155 00:05:29,630 --> 00:05:30,810 Anytime you see the word local, 156 156 00:05:30,810 --> 00:05:32,270 I want you to think about private, 157 157 00:05:32,270 --> 00:05:34,700 and then you'll be able to answer these types of questions. 158 158 00:05:34,700 --> 00:05:37,017 Now, let me show you what all this looks like on a diagram. 159 159 00:05:37,017 --> 00:05:40,255 Here, I have NAT. Now, where are each of these things? 160 160 00:05:40,255 --> 00:05:42,600 If I'm dealing with my inside local, 161 161 00:05:42,600 --> 00:05:45,555 that is my private IP address referencing an inside device, 162 162 00:05:45,555 --> 00:05:47,589 which is one of the private IP addresses, 163 163 00:05:47,589 --> 00:05:50,260 referencing an inside device in this diagram. 164 164 00:05:50,260 --> 00:05:53,594 Well, there might be something like 10.0.1.101. 165 165 00:05:53,594 --> 00:05:57,418 Which would be PC1, that is my inside local address. 166 166 00:05:57,418 --> 00:06:00,760 Then, I have to reference an inside global address, 167 167 00:06:00,760 --> 00:06:01,750 which is a router. 168 168 00:06:01,750 --> 00:06:05,187 And for our case, that would be 78.1.45.1 169 169 00:06:05,187 --> 00:06:07,810 It's inside, because it's my network, 170 170 00:06:07,810 --> 00:06:09,263 and it's global because it's public. 171 171 00:06:09,263 --> 00:06:12,788 As far as the outside local, that's our private IP address 172 172 00:06:12,788 --> 00:06:14,538 that references an outside device. 173 173 00:06:14,538 --> 00:06:17,128 For us, that would be the inside of this router, 174 174 00:06:17,128 --> 00:06:21,161 or, 10.0.1.1 because that is our outside device, 175 175 00:06:21,161 --> 00:06:23,055 it's our boundary device, that router. 176 176 00:06:23,055 --> 00:06:25,677 And then, if I wanted to talk about my outside global, 177 177 00:06:25,677 --> 00:06:29,283 that's my public IP address, referencing an outside device. 178 178 00:06:30,321 --> 00:06:33,482 That would be the server, 66.75.58.124 179 179 00:06:33,482 --> 00:06:36,147 All four of these, have to work together, 180 180 00:06:36,147 --> 00:06:38,147 for us to be able to get the information 181 181 00:06:39,001 --> 00:06:40,909 from RPC, 10.0.1.101, 182 182 00:06:40,909 --> 00:06:43,538 from that local private IP address, 183 183 00:06:43,538 --> 00:06:45,954 out to the server, that I want to make the connection to. 184 184 00:06:45,954 --> 00:06:48,109 Now, how does NAT work? 185 185 00:06:48,109 --> 00:06:50,040 Well, let's take a look at this diagram, 186 186 00:06:50,040 --> 00:06:51,767 where I have PC1 and PC2, 187 187 00:06:51,767 --> 00:06:54,263 who want to make a request of a single server. 188 188 00:06:54,263 --> 00:06:58,093 Now PC1 and PC2, both have private IP addresses, 189 189 00:06:58,093 --> 00:07:00,502 which are not routable outside my network. 190 190 00:07:00,502 --> 00:07:02,626 Once, I get to the router, they're going to be dropped, right? 191 191 00:07:02,626 --> 00:07:05,756 So, when they send a request, from their source IP, 192 192 00:07:05,756 --> 00:07:08,010 that's their private IP. 193 193 00:07:08,010 --> 00:07:10,980 That would be the 10.0.1.101 194 194 00:07:10,980 --> 00:07:11,904 or 195 195 00:07:11,904 --> 00:07:13,353 10.0.1.102 196 196 00:07:13,353 --> 00:07:14,970 Now, as part of that request, 197 197 00:07:14,970 --> 00:07:16,740 they're going to put the destination of the server 198 198 00:07:16,740 --> 00:07:17,738 that they want to get to. 199 199 00:07:17,738 --> 00:07:19,350 And so, they're going to send that request 200 200 00:07:19,350 --> 00:07:21,557 with their default gateway, over to the router. 201 201 00:07:21,557 --> 00:07:23,520 And this is where the NAT happens, 202 202 00:07:23,520 --> 00:07:25,003 because it's a NAT enabled router. 203 203 00:07:25,003 --> 00:07:26,485 When the router gets that request, 204 204 00:07:26,485 --> 00:07:30,640 it's going to keep track of the fact that 10.0.1.101 205 205 00:07:30,640 --> 00:07:32,270 was for PC1 206 206 00:07:32,270 --> 00:07:34,286 and the.102 was for PC2. 207 207 00:07:34,286 --> 00:07:36,070 And it's going to assign each of them, 208 208 00:07:36,070 --> 00:07:38,240 an inside global address from its pool 209 209 00:07:38,240 --> 00:07:39,703 of public IP addresses. 210 210 00:07:40,668 --> 00:07:44,721 In this case, that 78.1.45.101 211 211 00:07:44,721 --> 00:07:46,870 and 78.1.45.102 212 212 00:07:46,870 --> 00:07:48,610 Now, it's going to strip off the source, 213 213 00:07:48,610 --> 00:07:50,087 that was those private IP addresses 214 214 00:07:50,087 --> 00:07:52,214 and put on these inside global addresses, 215 215 00:07:52,214 --> 00:07:53,682 which is publicly routable. 216 216 00:07:53,682 --> 00:07:56,029 And then, they're going to send the packet off to the server. 217 217 00:07:56,029 --> 00:07:58,061 When the request comes back to the router, 218 218 00:07:58,061 --> 00:08:00,480 it's going to strip off those inside global addresses, 219 219 00:08:00,480 --> 00:08:02,630 put back on the inside local addresses 220 220 00:08:02,630 --> 00:08:05,831 and send it back to PC1 and PC2, respectively. 221 221 00:08:05,831 --> 00:08:07,840 That's essentially how NAT works 222 222 00:08:07,840 --> 00:08:10,695 and this can be either done statically or dynamically 223 223 00:08:10,695 --> 00:08:13,300 based on those IP addresses and the pool that's 224 224 00:08:13,300 --> 00:08:15,835 being there, in reserve, at that NAT enabled router. 225 225 00:08:15,835 --> 00:08:18,437 Now, when we deal with your network at home though, 226 226 00:08:18,437 --> 00:08:19,960 we're using PAT, 227 227 00:08:19,960 --> 00:08:22,981 Like I said before. This is port address translation. 228 228 00:08:22,981 --> 00:08:24,563 The reason for this is it only requires 229 229 00:08:24,563 --> 00:08:26,604 one IP address on your router. 230 230 00:08:26,604 --> 00:08:29,310 Now, you can't just take one and give it directly 231 231 00:08:29,310 --> 00:08:30,488 to PC1 or PC2 though, 232 232 00:08:30,488 --> 00:08:32,915 because, then, only one of them can get online at a time. 233 233 00:08:32,915 --> 00:08:35,526 So instead, We're going to use ports, 234 234 00:08:35,526 --> 00:08:37,587 to keep track of the different segments that we're doing. 235 235 00:08:37,587 --> 00:08:40,926 So, when PC1 and PC2, make a request to the router, 236 236 00:08:40,926 --> 00:08:43,092 the router is going to send off a request 237 237 00:08:43,092 --> 00:08:44,382 from its source address. 238 238 00:08:44,382 --> 00:08:46,482 and it's going to specify a port number, 239 239 00:08:46,482 --> 00:08:48,023 to keep track of those requests. 240 240 00:08:48,023 --> 00:08:50,340 When the request comes back from the server 241 241 00:08:50,340 --> 00:08:51,353 on that specific port, 242 242 00:08:51,353 --> 00:08:53,198 it then knows, I need to take that traffic 243 243 00:08:53,198 --> 00:08:56,417 and forward it to either PC1 or PC2, respectively, 244 244 00:08:56,417 --> 00:08:58,023 depending on which port number it was. 245 245 00:08:58,023 --> 00:09:00,184 And that's why PAT is so popular today, 246 246 00:09:00,184 --> 00:09:02,884 because we only have to have one public IP, 247 247 00:09:02,884 --> 00:09:06,039 and we can have twenty, fifty, a hundred devices, 248 248 00:09:06,039 --> 00:09:08,380 all sitting behind that router, 249 249 00:09:08,380 --> 00:09:10,633 and being kept track of based on those ports.