1 00:00:00,349 --> 00:00:02,341 Network Address Translation. 2 00:00:02,341 --> 00:00:04,301 Network Address Translation or NAT 3 00:00:04,301 --> 00:00:06,643 is the process of changing an IP address 4 00:00:06,643 --> 00:00:09,051 while it transits across a router. 5 00:00:09,051 --> 00:00:11,548 Now in Network+, we discussed how this was used 6 00:00:11,548 --> 00:00:14,279 because we wanted to conserve public IP addresses 7 00:00:14,279 --> 00:00:16,590 because they were limited in IPv4. 8 00:00:16,590 --> 00:00:18,000 In Security+, though, 9 00:00:18,000 --> 00:00:20,600 we are going to gain an additional benefit when we use NAT, 10 00:00:20,600 --> 00:00:22,550 we can actually hide our internal networks 11 00:00:22,550 --> 00:00:24,070 from attackers. 12 00:00:24,070 --> 00:00:26,139 Now, the most commonly used type of NAT 13 00:00:26,139 --> 00:00:29,320 is what we call Port Address Translation or PAT. 14 00:00:29,320 --> 00:00:31,491 This is where we have a single public IP address 15 00:00:31,491 --> 00:00:32,531 assigned to a router 16 00:00:32,531 --> 00:00:34,640 and all of the private IP addresses 17 00:00:34,640 --> 00:00:36,669 that are assigned inside to our host. 18 00:00:36,669 --> 00:00:38,807 In your small office, home office network, 19 00:00:38,807 --> 00:00:40,919 this is most likely what you are using. 20 00:00:40,919 --> 00:00:43,929 Now, when a host wants to communicate out over the WAN, 21 00:00:43,929 --> 00:00:46,156 it's going to send the request to the router 22 00:00:46,156 --> 00:00:47,817 and the router is then going to forward the request 23 00:00:47,817 --> 00:00:48,999 out to the Internet, 24 00:00:48,999 --> 00:00:50,666 to the server that it's trying to get to 25 00:00:50,666 --> 00:00:52,199 on behalf of the host. 26 00:00:52,199 --> 00:00:53,147 And when it does this, 27 00:00:53,147 --> 00:00:55,427 it keeps track of the translation it does 28 00:00:55,427 --> 00:00:57,728 by using a unique random high port number 29 00:00:57,728 --> 00:00:59,227 for each request. 30 00:00:59,227 --> 00:01:01,224 This means if the attacker is getting your network 31 00:01:01,224 --> 00:01:02,323 from the outside, 32 00:01:02,323 --> 00:01:04,763 they are only going to see that single public IP address 33 00:01:04,763 --> 00:01:05,635 of the router 34 00:01:05,635 --> 00:01:07,093 and they are not going to see the fact that you have 35 00:01:07,093 --> 00:01:11,813 one, five, ten, or 100 hosts inside of your network, 36 00:01:11,813 --> 00:01:13,142 and they are not going to be able to exactly know 37 00:01:13,142 --> 00:01:14,315 how many devices there are 38 00:01:14,315 --> 00:01:15,824 or what kind they are. 39 00:01:15,824 --> 00:01:17,846 So, for the Security+ exam, 40 00:01:17,846 --> 00:01:20,190 in addition to knowing about NAT and PAT, 41 00:01:20,190 --> 00:01:21,148 you should remember 42 00:01:21,148 --> 00:01:23,686 that there is public and private IP scopes. 43 00:01:23,686 --> 00:01:24,519 Now, when you start talking about 44 00:01:24,519 --> 00:01:25,852 private IP ranges, 45 00:01:25,852 --> 00:01:26,685 you should have learned those 46 00:01:26,685 --> 00:01:28,947 back in A+ and Network+. 47 00:01:28,947 --> 00:01:31,342 If you didn't, I'm going to give you a quick review. 48 00:01:31,342 --> 00:01:33,936 Class A is anything that starts with a 10, 49 00:01:33,936 --> 00:01:38,019 so 10.0.0.0 all the way up through 10.255.255.255. 50 00:01:40,225 --> 00:01:43,181 Now in class B, we have IP addresses that start with 51 00:01:43,181 --> 00:01:46,848 172.16.0.0 all the way up through 172.31.0.0, 52 00:01:50,627 --> 00:01:53,627 essentially, anything that starts with a 172.16 53 00:01:53,627 --> 00:01:56,044 all the way up through 172.31. 54 00:01:56,955 --> 00:01:59,217 Class C is really easy to remember as well, 55 00:01:59,217 --> 00:02:00,990 and it's probably what you are using at home. 56 00:02:00,990 --> 00:02:05,073 It's 192.168.0.0 all the way up to 192.168.255.255. 57 00:02:08,412 --> 00:02:11,088 So, if it starts with a 192.168, 58 00:02:11,088 --> 00:02:13,385 it is also a private IP address. 59 00:02:13,385 --> 00:02:15,054 Remember, private IP addresses 60 00:02:15,054 --> 00:02:17,033 cannot be transmitted over the Internet. 61 00:02:17,033 --> 00:02:19,474 So instead, once they hit your external router, 62 00:02:19,474 --> 00:02:21,603 it's going to use either PAT or NAT 63 00:02:21,603 --> 00:02:24,075 to give it a public IP address and a port number 64 00:02:24,075 --> 00:02:25,905 to send the information out to the Internet 65 00:02:25,905 --> 00:02:28,072 and then receive it back.