1 00:00:00,450 --> 00:00:07,170 In the section we're going to discuss network address translation or not and port address translation 2 00:00:07,200 --> 00:00:08,300 or pat. 3 00:00:08,490 --> 00:00:11,090 We'll discuss why Knecht is required. 4 00:00:11,190 --> 00:00:14,830 Why do we use net in networks today. 5 00:00:14,850 --> 00:00:22,020 We'll also discuss the difference between Nat and Pat and we'll discuss the Cisco term overloading which 6 00:00:22,020 --> 00:00:29,790 implies that a lot of network engineers talk about that even though they actually mean packed. 7 00:00:29,940 --> 00:00:33,100 So we need to understand the differences between those two terms. 8 00:00:33,180 --> 00:00:38,460 And as always I'd like to demonstrate how to set up Nat using the command line interface. 9 00:00:38,640 --> 00:00:46,920 We'll look at different types of not including static not dynamic Nat and Pat or overloading as Cisco 10 00:00:46,920 --> 00:00:50,480 call it before going any further. 11 00:00:51,610 --> 00:00:53,340 Here's a demonstration. 12 00:00:53,340 --> 00:00:56,710 I've disabled all network interface cards on my PC. 13 00:00:58,020 --> 00:01:00,510 Except for the wireless interface card. 14 00:01:00,720 --> 00:01:09,270 When I look at the details of that card I can see that my IP address is 1 9 2 1 6 8 1 89 and I'll have 15 00:01:09,270 --> 00:01:17,270 a default gateway of 1 9 2 1 6 8 1 2 5 4 I can view that in a CMD prompt as an example. 16 00:01:17,280 --> 00:01:25,350 So on my PC type IP config see the IP address see the default gateway. 17 00:01:25,490 --> 00:01:28,650 I can ping Google dot com 18 00:01:32,960 --> 00:01:37,290 so notice I'm getting replies from Google dot com. 19 00:01:37,450 --> 00:01:39,420 I can access Google dot com. 20 00:01:39,460 --> 00:01:42,000 So here's the Google web site. 21 00:01:42,160 --> 00:01:52,970 But when I type what is my IP address into Google I'm told by Google that this is my public IP address. 22 00:01:56,670 --> 00:02:05,570 IP config again shows me that my internal IP address or private IP address is 1 9 2 1 6 8 1 89. 23 00:02:05,700 --> 00:02:12,000 But my public IP address is this. 24 00:02:12,010 --> 00:02:19,420 So in this example my internet router at home is connected to the Internet and this route is configured 25 00:02:19,420 --> 00:02:21,170 with DHP. 26 00:02:21,190 --> 00:02:26,310 It's allocating IP addresses to devices internally using DHP. 27 00:02:26,560 --> 00:02:33,490 And one of those IP addresses was allocated to my local PC but when I go onto the internet my address 28 00:02:33,580 --> 00:02:41,800 used is a public IP address so a network address translation essentially translates a private IP address 29 00:02:42,070 --> 00:02:49,390 which is non-radical on the Internet to publicly ratable IP address your public IP address is typically 30 00:02:49,420 --> 00:02:55,610 allocated to you by your service provider which in my case is British Telecom or BT. 31 00:02:55,720 --> 00:03:04,130 Here in the UK in large networks companies may register their own public IP addresses Yarrow's some 32 00:03:04,130 --> 00:03:19,510 well known examples Hewlett-Packard own $15.00 flechette and 16 Apple own 17 MIT 18 forward 19 AT&T 33 00:03:19,510 --> 00:03:22,570 32 and so on. 34 00:03:23,110 --> 00:03:27,780 And IBM is an example nine dot sera sera sera. 35 00:03:27,890 --> 00:03:37,310 So as an example if you working with HP or with an apple you may not be using a private IP address such 36 00:03:37,310 --> 00:03:38,290 as this. 37 00:03:38,330 --> 00:03:43,210 You may actually have a public IP address allocated to your PC. 38 00:03:43,220 --> 00:03:49,070 These are globally readable public IP addresses that were registered by some of the largest companies 39 00:03:49,070 --> 00:03:53,110 in the world but IP addresses are running out. 40 00:03:53,150 --> 00:03:58,990 So in most small medium businesses today you'll be using a private IP address internally.