1 00:00:07,860 --> 00:00:12,630 This is one of multiple videos discussing network address, translation or net. 2 00:00:12,990 --> 00:00:23,370 In a previous video I showed you how to configure static net translations to allow outside hosts or 3 00:00:23,370 --> 00:00:32,340 hosts on the internet access to multiple internal servers running in your local network router to in 4 00:00:32,340 --> 00:00:43,080 this example is netting the three servers on the left to public IP addresses in the 8.8.8 range, making 5 00:00:43,080 --> 00:00:45,570 them available to this PC. 6 00:00:45,810 --> 00:00:55,050 Now the issue here is that you are using an external or public IP address per internal server. 7 00:00:56,680 --> 00:01:03,010 Is it possible to use a single IP address such as an IP address at your home? 8 00:01:05,360 --> 00:01:11,450 To expose multiple servers or devices to the Internet. 9 00:01:14,700 --> 00:01:17,160 So in other words, can you set up servers? 10 00:01:18,220 --> 00:01:26,170 In your home network or small medium business network and allow people to access those servers using 11 00:01:26,170 --> 00:01:28,150 the same IP address. 12 00:01:29,080 --> 00:01:30,640 And the answer is yes. 13 00:01:30,730 --> 00:01:34,540 So at the moment I've got four net commands configured. 14 00:01:35,430 --> 00:01:38,850 What I've done is configure gigabit zero one. 15 00:01:40,060 --> 00:01:44,470 As the outside interface on this router and the other interfaces. 16 00:01:44,470 --> 00:01:50,380 Gigabit zero zero, two and three are configured as inside NAT interfaces. 17 00:01:51,110 --> 00:01:58,040 See my previous video for the configuration of static net using multiple IP addresses once again. 18 00:01:58,070 --> 00:02:07,040 But here what we're going to do is use the command IP nat inside source because we want to net these 19 00:02:07,040 --> 00:02:10,639 servers to an individual IP address. 20 00:02:10,850 --> 00:02:18,560 So I'm going to use the command IP Nat inside source static, the inside local IP address of the server. 21 00:02:18,590 --> 00:02:26,360 In other words, its real IP address is 10.1, 1.1 and we're going to match it to a virtual IP address 22 00:02:26,360 --> 00:02:28,640 of 8.8 to 8.1. 23 00:02:29,150 --> 00:02:35,570 Now, if we did that, we would be using that entire IP address for that individual server. 24 00:02:35,960 --> 00:02:41,840 So what are we going to do here rather is specify TCP IP or UDP. 25 00:02:42,290 --> 00:02:48,890 So TCP IP, and now we're going to specify the inside IP address and the port number on that server 26 00:02:48,890 --> 00:02:50,360 is going to be 23. 27 00:02:50,990 --> 00:02:54,650 And the virtual IP address of the server is going to be this. 28 00:02:54,650 --> 00:02:59,450 And in this example, I'll use Port 23 extendable. 29 00:02:59,840 --> 00:03:07,820 So basically what I'm saying is that when this device sends traffic to Port 23 and destination IP address 30 00:03:07,820 --> 00:03:13,340 8.828.1, the router is going to net it and send the traffic to that server. 31 00:03:13,940 --> 00:03:16,010 So let's test it rather. 32 00:03:16,010 --> 00:03:28,370 Three In this example is acting as our PC, so I'll telnet to 8.8.8.1 and notice I can log in to server 33 00:03:28,370 --> 00:03:36,350 one over there and to prove it we can type show IP interface brief to see the IP address of the server. 34 00:03:38,900 --> 00:03:39,170 Okay. 35 00:03:39,170 --> 00:03:41,090 But now how do you do this? 36 00:03:42,490 --> 00:03:44,770 For the other service. 37 00:03:45,730 --> 00:03:53,050 So in this example, I'm going to use a random port number or a femoral port number of 65,023. 38 00:03:54,700 --> 00:03:59,170 And change that to 10.1, 2.2. 39 00:03:59,590 --> 00:04:05,740 So in other words, when traffic gets sent by this PC to the router with the destination IP address 40 00:04:05,740 --> 00:04:16,930 of 8.8 to 8.1 destination port number of 65,023, the right is going to net it to this internal IP address. 41 00:04:17,870 --> 00:04:22,040 And change the port number to 23. 42 00:04:22,680 --> 00:04:25,530 So on router three. 43 00:04:27,030 --> 00:04:33,510 When we use the Telnet IP address question mark command, we can now specify a port number. 44 00:04:33,720 --> 00:04:36,720 So 65,023. 45 00:04:37,450 --> 00:04:38,770 Connection is opened. 46 00:04:39,760 --> 00:04:42,580 And we are now en route of for. 47 00:04:45,110 --> 00:04:48,860 Show IP interface brief. 48 00:04:49,220 --> 00:04:53,090 We are on router four but. 49 00:04:55,130 --> 00:04:56,660 Using the same. 50 00:04:58,580 --> 00:04:59,630 IP address. 51 00:04:59,870 --> 00:05:06,320 8.8.8.1 but a different port number, which means the traffic goes to a different server. 52 00:05:06,830 --> 00:05:08,180 Let's create another one. 53 00:05:08,180 --> 00:05:09,630 So IP. 54 00:05:09,650 --> 00:05:13,280 Net inside source static TCP IP. 55 00:05:16,460 --> 00:05:18,500 Let's send it to Rada five. 56 00:05:18,530 --> 00:05:20,450 Acting Server three. 57 00:05:20,570 --> 00:05:25,070 But in this case, I'll use a port number of 65,024. 58 00:05:25,820 --> 00:05:31,550 So show run pipe include natch. 59 00:05:31,940 --> 00:05:35,600 Shows us the static net commands. 60 00:05:36,620 --> 00:05:42,620 Let's move that over here I'll exert a lot of for some back end road of three which is acting as our 61 00:05:42,620 --> 00:05:46,070 PC show IP interface brief notice. 62 00:05:46,070 --> 00:05:47,690 This is the IP address of the PC. 63 00:05:47,690 --> 00:05:48,740 It's on the internet. 64 00:05:50,300 --> 00:05:53,330 And what I'll do now is telnet to port. 65 00:05:54,610 --> 00:05:56,800 65,024. 66 00:05:59,680 --> 00:06:00,310 Name one. 67 00:06:00,310 --> 00:06:05,170 Writer five with IP Address 10.1 3.3. 68 00:06:05,590 --> 00:06:12,460 What I'll do now is use the command control shift six X to jump back to router three and go to port 69 00:06:12,460 --> 00:06:15,100 number 65,023. 70 00:06:16,500 --> 00:06:24,120 I'm on rather for control shift six X to jump back show sessions shows me that I've got two sessions 71 00:06:24,120 --> 00:06:24,690 open. 72 00:06:26,270 --> 00:06:28,820 What I'll do now is telnet to port T3. 73 00:06:30,230 --> 00:06:37,370 Now I'm on rather one control shift six x shows that I've got three sessions open. 74 00:06:38,540 --> 00:06:43,220 Show IP Nat en route a two shows me those connections. 75 00:06:43,400 --> 00:06:53,330 So this PC 8.828.4, which is this PC here, has initiated sessions to 828 2 to 8.1 port 23, which 76 00:06:53,330 --> 00:06:54,590 is going to that host. 77 00:06:55,230 --> 00:06:59,970 One of the old TCP sessions is still held in the NAT translation table. 78 00:07:00,000 --> 00:07:01,740 Hence we're seeing two of them. 79 00:07:02,130 --> 00:07:10,800 But we've also got the same PC sending traffic to eight today to date one but port 65,023. 80 00:07:11,280 --> 00:07:14,100 That's going to different host on port 23. 81 00:07:14,460 --> 00:07:16,260 And we've also got this entry. 82 00:07:16,560 --> 00:07:25,890 So that's an example of how to use the same global IP address or Internet IP address for multiple internal 83 00:07:25,890 --> 00:07:27,910 hosts or devices. 84 00:07:27,930 --> 00:07:34,020 So once again, if you were at home and you wanted to make your devices available on the Internet, 85 00:07:34,020 --> 00:07:37,800 but you only had one public IP address, this is how you do it. 86 00:07:38,100 --> 00:07:46,080 The only thing to remember is that you can't use the same port number for multiple internal devices 87 00:07:46,260 --> 00:07:50,610 because otherwise the router can't differentiate between the net translations. 88 00:07:50,610 --> 00:07:56,530 So hence we use different port numbers for the different hosts. 89 00:07:56,550 --> 00:07:59,970 Even though it's the same external IP address. 90 00:08:00,390 --> 00:08:02,300 I hope you've found this useful. 91 00:08:02,310 --> 00:08:08,430 This is out of the scope of a CCNA exam, but hopefully gives you some real world knowledge that you 92 00:08:08,430 --> 00:08:09,270 can apply. 93 00:08:09,480 --> 00:08:14,310 If you enjoyed this video, please like it and I wish you all the very best.