1 00:00:08,400 --> 00:00:13,440 This is one of multiple network address translation or NAT videos. 2 00:00:14,220 --> 00:00:15,990 This is a troubleshooting video. 3 00:00:16,079 --> 00:00:23,700 In this scenario, you've been told that some hosts in the internal network are not able to connect 4 00:00:23,700 --> 00:00:24,780 to the Internet. 5 00:00:25,710 --> 00:00:27,390 In this Janus three topology. 6 00:00:27,390 --> 00:00:32,159 I've got four routers, router two and router three are acting as PCs. 7 00:00:32,580 --> 00:00:39,030 They have IP routing disabled, they have their default gateways configured as router one. 8 00:00:39,330 --> 00:00:41,970 Rather, one is going to act as our network address. 9 00:00:41,970 --> 00:00:45,930 Translation router and router four is going to act as Google. 10 00:00:46,290 --> 00:00:52,890 So let's test the network can write a one ping the DNS server. 11 00:00:53,220 --> 00:00:57,600 So router four pretending to be the Google DNS server. 12 00:00:57,720 --> 00:00:58,950 Yes, it can. 13 00:01:00,400 --> 00:01:01,840 What about rather three? 14 00:01:04,400 --> 00:01:06,640 Doesn't look like it's able to ping. 15 00:01:08,000 --> 00:01:08,960 Let's investigate. 16 00:01:08,960 --> 00:01:10,330 So show IP rot. 17 00:01:10,340 --> 00:01:16,670 We can see that IP routing is disabled on this router, but it's default gateways configured as ten 18 00:01:16,670 --> 00:01:17,450 111. 19 00:01:18,760 --> 00:01:23,860 What about on rather to rather to has the same configuration. 20 00:01:24,670 --> 00:01:37,210 Wrote to campaign ten 111 and can ping google router three can ping ten 111. 21 00:01:38,020 --> 00:01:40,990 We could trace to google. 22 00:01:41,410 --> 00:01:44,350 It gets to its default gateway ten 111. 23 00:01:45,920 --> 00:01:48,290 But then nothing happens. 24 00:01:51,840 --> 00:01:54,960 So we have a timeout on rudder one. 25 00:01:56,010 --> 00:02:00,150 So on router one, let's confirm the IP address in firstly. 26 00:02:01,530 --> 00:02:05,670 If zero one has an IP address of ten 111. 27 00:02:06,960 --> 00:02:08,910 That's the inside of the network. 28 00:02:10,470 --> 00:02:15,040 If zero zero has an IP address of 8228228244. 29 00:02:15,540 --> 00:02:19,260 So let's do a debug on the strata. 30 00:02:21,000 --> 00:02:22,260 Debug I peanut. 31 00:02:23,340 --> 00:02:23,940 Wrote it too. 32 00:02:23,940 --> 00:02:30,630 Was able to ping Google before and still can and we can see the natural translation taking place. 33 00:02:32,110 --> 00:02:34,570 When rudder three pings google.com. 34 00:02:34,570 --> 00:02:37,540 We don't see any net translations. 35 00:02:38,260 --> 00:02:39,520 Show IP. 36 00:02:41,200 --> 00:02:42,640 Net translations. 37 00:02:44,310 --> 00:02:46,710 So we see a net translation for. 38 00:02:47,470 --> 00:02:55,330 REPORTER two That's the IP address of WRITER two So show IP Interface Brief will show us that. 39 00:02:57,040 --> 00:03:00,550 So we can see the net translation four out of two. 40 00:03:00,790 --> 00:03:03,310 But we don't see a net translation. 41 00:03:03,310 --> 00:03:04,360 Four out of three. 42 00:03:04,870 --> 00:03:08,080 What happens if we clear the net translations? 43 00:03:10,790 --> 00:03:13,400 So there are no natural translations at the moment. 44 00:03:14,000 --> 00:03:20,510 When I ping from router three to Google we suddenly see translations. 45 00:03:21,400 --> 00:03:23,560 And the pings start succeeding. 46 00:03:24,460 --> 00:03:27,460 So Ken rather to paying google.com. 47 00:03:30,340 --> 00:03:34,240 Notice four out of two now no longer paying google.com. 48 00:03:35,020 --> 00:03:37,360 Let's clear the net translations again. 49 00:03:40,520 --> 00:03:43,100 Rather two is now able to paint google.com. 50 00:03:46,300 --> 00:03:48,100 But rather three is not. 51 00:03:51,030 --> 00:04:00,540 So it looks like when we clear the net translations, one device is able to connect to Google should 52 00:04:00,540 --> 00:04:01,020 run. 53 00:04:06,120 --> 00:04:13,080 If zero zero is correctly configured with an IP address and is configured as the outside NAT interface. 54 00:04:15,000 --> 00:04:22,590 If 0/1 has the correct insight IP address and is configured as the inside NAT interface. 55 00:04:24,590 --> 00:04:25,340 Okay. 56 00:04:25,370 --> 00:04:27,140 Can you see the problem? 57 00:04:27,920 --> 00:04:29,450 What's going on here? 58 00:04:30,770 --> 00:04:33,170 Notice we're not clear the net translation again. 59 00:04:35,900 --> 00:04:41,120 And then ping from Writer three, which wasn't able to ping previously. 60 00:04:41,420 --> 00:04:49,220 The pings now succeed show IP net translation we now see a net translation four out of three. 61 00:04:50,720 --> 00:04:56,930 So going back through the configuration and I'll scroll down to the net config. 62 00:04:58,130 --> 00:04:59,900 Can you see the problem? 63 00:05:00,890 --> 00:05:01,460 Okay. 64 00:05:01,490 --> 00:05:10,070 Have a look at this IP Nat inside source list one which is pointing to access list one that means that 65 00:05:10,070 --> 00:05:16,550 any IP address will be netted, but it's pointing to a pool called my pool. 66 00:05:18,510 --> 00:05:28,890 The net pool is configured with a starting IP address of 82828 8 to 2 and an ending IP address of 8.8. 67 00:05:28,890 --> 00:05:29,880 8 to 2. 68 00:05:30,740 --> 00:05:34,520 That means we've only put one IP address in the pool. 69 00:05:34,760 --> 00:05:40,790 Hence only one internal host can be netted at any given time. 70 00:05:42,310 --> 00:05:43,990 So let's remove this. 71 00:05:52,760 --> 00:05:54,080 We told her we can't remove it. 72 00:05:54,080 --> 00:05:56,570 So let's clear the IP net translations. 73 00:05:58,230 --> 00:05:59,970 Translation star. 74 00:06:01,400 --> 00:06:03,020 And try and remove it again. 75 00:06:03,140 --> 00:06:04,490 So it's removed now. 76 00:06:07,170 --> 00:06:14,310 What we should do is add additional IP addresses to the pool, so I'll add from 2 to 20. 77 00:06:14,940 --> 00:06:20,220 Previously it was from 8 to 8 two 8 to 2 to 8282822. 78 00:06:20,490 --> 00:06:23,160 But now it's going from 2 to 20. 79 00:06:23,760 --> 00:06:26,550 So show run pipe include. 80 00:06:27,910 --> 00:06:32,160 Net will show us that configuration. 81 00:06:33,540 --> 00:06:35,340 So Ken wrote a three ping. 82 00:06:36,560 --> 00:06:37,010 Google. 83 00:06:37,010 --> 00:06:41,060 Yes, it can can run a two ping Google. 84 00:06:41,940 --> 00:06:42,790 Yes, it can. 85 00:06:42,830 --> 00:06:50,130 It took it a while, but rather to campaign Google, write a three campaign Google and we see the net 86 00:06:50,130 --> 00:06:52,020 translations for both of them. 87 00:06:52,530 --> 00:06:56,250 Notice please, that the one device is netted. 88 00:06:57,190 --> 00:07:07,870 28282823 and the other one is netted 282882 data to the show IP net translation shows us that two addresses 89 00:07:07,870 --> 00:07:10,230 in the pool have been used. 90 00:07:10,810 --> 00:07:13,330 Show IP net statistics. 91 00:07:14,950 --> 00:07:18,400 At the moment we have six dynamic translations. 92 00:07:19,730 --> 00:07:23,510 Notice our poll shows us the list of IP addresses. 93 00:07:24,020 --> 00:07:30,470 So we have a starting address of 8.82822 and ending of 82822 820. 94 00:07:31,010 --> 00:07:37,850 There are 19 addresses in the pool and two have been allocated, so this would be another good command 95 00:07:37,850 --> 00:07:39,020 to use. 96 00:07:39,950 --> 00:07:41,540 Let's clear the net. 97 00:07:42,220 --> 00:07:44,770 Translation and remove the command. 98 00:07:50,130 --> 00:07:51,720 And I'll edit back. 99 00:07:53,800 --> 00:07:58,720 With only a single IP address in the pool. 100 00:07:59,890 --> 00:08:02,800 To show IP net translations. 101 00:08:03,460 --> 00:08:05,170 No translations at the moment. 102 00:08:05,380 --> 00:08:08,710 Show IP net statistics. 103 00:08:09,870 --> 00:08:13,380 Notice we only have one IP address in the pool. 104 00:08:13,380 --> 00:08:15,390 So when router three pings. 105 00:08:17,900 --> 00:08:19,880 And we look at the statistics again. 106 00:08:20,530 --> 00:08:24,340 Notice 100% of the pool is allocated. 107 00:08:25,360 --> 00:08:33,400 So that's why Writer two is not able to ping because the, because the pool consists of a single IP 108 00:08:33,400 --> 00:08:35,679 address and it's already been allocated. 109 00:08:36,590 --> 00:08:39,140 So again, be careful with your pools. 110 00:08:40,150 --> 00:08:43,299 You need to allocate enough addresses to the pool. 111 00:08:43,900 --> 00:08:46,300 So clear the net translations again. 112 00:08:51,710 --> 00:08:52,790 Well, remove. 113 00:08:55,050 --> 00:08:55,950 That pool. 114 00:08:57,850 --> 00:08:59,860 Configure it again with. 115 00:09:01,290 --> 00:09:08,940 Let's say, from 2 to 25 to show IP net statistics. 116 00:09:10,610 --> 00:09:14,630 We have 24 dresses in the pool in this range. 117 00:09:14,990 --> 00:09:16,580 None have been allocated. 118 00:09:17,760 --> 00:09:20,730 I'll send some traffic from both writer to and writer three. 119 00:09:24,590 --> 00:09:28,550 So we can see that rather too is being netted and so is rather three. 120 00:09:29,210 --> 00:09:31,220 And now when we look at the statistics. 121 00:09:32,200 --> 00:09:36,790 Notice 24 addresses are available to have been allocated. 122 00:09:37,300 --> 00:09:41,710 So that was an example of how to troubleshoot, network address translation or NAT. 123 00:09:42,720 --> 00:09:44,820 I hope you found the video useful. 124 00:09:44,940 --> 00:09:50,160 If you enjoyed it, please like it and please subscribe to my YouTube channel. 125 00:09:50,550 --> 00:09:52,800 I wish you all the very best.