1 00:00:00,910 --> 00:00:08,200 So exit out of the Telnet session from rather three four rather one two, rather three and we can see 2 00:00:08,200 --> 00:00:10,270 some net translations taking place. 3 00:00:10,720 --> 00:00:12,640 Show IP net translation. 4 00:00:12,850 --> 00:00:18,040 We can see our two net translations in the table, which will time out after a period of time. 5 00:00:19,820 --> 00:00:20,700 Wrote a four. 6 00:00:20,720 --> 00:00:24,260 I'll also exit out of the Telnet session. 7 00:00:26,140 --> 00:00:30,310 Currently we've got those two natural translation entries. 8 00:00:31,160 --> 00:00:34,150 Let's do a Y shock capture. 9 00:00:34,160 --> 00:00:36,470 So I'm going to capture on the outside interface. 10 00:00:37,130 --> 00:00:41,570 And in this case, let's look at what's arriving at router three. 11 00:00:41,660 --> 00:00:43,520 So what's arriving on that port? 12 00:00:46,770 --> 00:00:48,990 I'm going to filter this for Telnet. 13 00:00:49,950 --> 00:00:54,840 And on writer one I'll telnet to router three. 14 00:00:56,570 --> 00:00:58,700 We can see the Telnet data. 15 00:00:59,350 --> 00:01:00,190 So. 16 00:01:02,140 --> 00:01:07,510 Some Telnet negotiation taking place and we being prompted for our password. 17 00:01:07,510 --> 00:01:10,870 So we see this in the Wireshark capture. 18 00:01:12,830 --> 00:01:16,430 What I'll do is enter a password of Cisco and log in. 19 00:01:17,640 --> 00:01:18,690 And here you can see. 20 00:01:18,690 --> 00:01:19,140 See? 21 00:01:19,140 --> 00:01:20,400 I see. 22 00:01:20,400 --> 00:01:23,640 Oh, there's the Cisco login password. 23 00:01:24,090 --> 00:01:32,020 But what's important to notice is the traffic is coming from a source of 8 to 1 one one going to 8112. 24 00:01:32,040 --> 00:01:38,880 So it looks like or appears like the traffic is coming from this host going to this host, whereas in 25 00:01:38,880 --> 00:01:41,940 actual fact, the traffic is coming from our one. 26 00:01:42,920 --> 00:01:50,240 But in the wide shot capture, we can see that all the communication is between 8112 and 8111. 27 00:01:50,390 --> 00:01:56,240 So in this example, a root of three prompt is being sent from router three to router one. 28 00:01:56,750 --> 00:01:58,400 Let's stop that capture. 29 00:01:59,690 --> 00:02:01,880 And have a look at it on this side. 30 00:02:03,470 --> 00:02:05,360 So I'll have a look at it on the switch. 31 00:02:06,160 --> 00:02:08,770 So on this part of the network here. 32 00:02:11,920 --> 00:02:17,920 I'll do a photo for Telnet once again and I'll exit out of the Telnet session. 33 00:02:18,760 --> 00:02:21,670 Notice this was still part of the same Telnet session. 34 00:02:21,700 --> 00:02:27,100 But notice now the address is from ten 11128112. 35 00:02:28,330 --> 00:02:29,410 His E. 36 00:02:30,380 --> 00:02:31,020 X. 37 00:02:31,190 --> 00:02:31,820 I. 38 00:02:31,850 --> 00:02:32,510 T. 39 00:02:33,720 --> 00:02:34,350 Exit. 40 00:02:36,490 --> 00:02:38,830 And then we have this session closed. 41 00:02:39,830 --> 00:02:47,930 So in this example, the traffic is from this IP address as the source to this IP address is the destination. 42 00:02:48,170 --> 00:02:52,050 But when it's on this interface, it's changed to 8111. 43 00:02:52,220 --> 00:02:55,130 So that's an example of Pat in real time. 44 00:02:55,430 --> 00:02:58,760 Let's do it with two devices. 45 00:03:02,430 --> 00:03:08,040 I'll do the caption now on this side, but have two talented sessions going at the same time. 46 00:03:10,770 --> 00:03:12,090 So Telnet. 47 00:03:14,270 --> 00:03:17,090 Rather one telnet to router three. 48 00:03:17,890 --> 00:03:20,770 And rather for telnet to router three. 49 00:03:22,520 --> 00:03:28,700 Notice on all the output you only see 8111 communicating with 8112. 50 00:03:29,000 --> 00:03:30,260 You don't see. 51 00:03:31,610 --> 00:03:37,250 That the communication is actually from writer one and of four and all the output. 52 00:03:37,250 --> 00:03:40,940 It looks like it's the same two devices communicating with each other. 53 00:03:43,200 --> 00:03:47,490 Whereas in actual fact, there are multiple devices communicating here. 54 00:03:49,100 --> 00:03:52,910 And not just a single source device talking to a single destination device. 55 00:03:53,240 --> 00:03:55,820 Now you can see that by looking at the port numbers. 56 00:03:55,820 --> 00:03:59,900 So for this session, the port number is 19207. 57 00:04:01,040 --> 00:04:02,780 So that's part of the same session. 58 00:04:03,290 --> 00:04:04,940 19207. 59 00:04:05,600 --> 00:04:08,030 But notice here, it's a different session. 60 00:04:08,030 --> 00:04:12,770 Number 3245732457. 61 00:04:13,800 --> 00:04:23,040 If we look at the net translations show IP net translation, we can see the actual port numbers used 62 00:04:23,040 --> 00:04:25,830 by the devices in the sessions. 63 00:04:26,960 --> 00:04:29,360 So three, two, four, five, seven. 64 00:04:29,600 --> 00:04:32,300 Scrolling down 19 to oh seven. 65 00:04:32,870 --> 00:04:38,900 So there's the first device, ten 111 and yes, the second 110 114. 66 00:04:40,470 --> 00:04:45,600 That's once again how the right is able to differentiate between the devices. 67 00:04:46,530 --> 00:04:49,520 Let's have a look at verbose output in the show. 68 00:04:49,530 --> 00:04:52,080 IP net translations verbose output. 69 00:04:52,410 --> 00:04:54,320 We can see when it was created. 70 00:04:54,330 --> 00:04:59,130 So this one was created 2 minutes and 38 seconds ago, this one, 2 minutes and 34 seconds ago. 71 00:04:59,400 --> 00:05:03,990 You can see the use and the timeout and what's left on these entries. 72 00:05:05,130 --> 00:05:14,010 What's important to remember for dynamic net translations such as this is that multiple internal IP 73 00:05:14,010 --> 00:05:17,580 addresses are being mated to a single external IP address. 74 00:05:17,760 --> 00:05:19,380 You mustn't forget. 75 00:05:21,070 --> 00:05:24,430 To include the overload keyword. 76 00:05:24,460 --> 00:05:29,380 If you forget that keyword, only one device will be able to access the internet. 77 00:05:29,830 --> 00:05:38,260 Overloading enables pat or port address translation, which allows multiple internal devices to share 78 00:05:38,260 --> 00:05:45,700 the same global IP address and the router that's doing the net or in this case, port address translation 79 00:05:45,700 --> 00:05:50,200 or Pat can differentiate between the sessions based on the port numbers.