1 00:00:13,260 --> 00:00:20,460 We've been told once again in this network that rather one is not able to ping the loopback of router 2 00:00:20,460 --> 00:00:21,180 four. 3 00:00:21,900 --> 00:00:27,930 So let's check what's happening in the network show IP protocols. 4 00:00:28,350 --> 00:00:32,009 We can see that rather one is running a routing protocol. 5 00:00:32,280 --> 00:00:39,690 In this case it's OSPF with process id one show IP ospf neighbor. 6 00:00:40,100 --> 00:00:48,840 Rather one has an OSPF neighbor relationship to router to the relationship is full, so that's good. 7 00:00:49,470 --> 00:00:59,850 Neighbor IP addresses this local interfaces this show IP router shows us that we are learning OSPF routes. 8 00:00:59,940 --> 00:01:01,650 So that is good. 9 00:01:02,730 --> 00:01:04,760 Can we ping the loopback of router two? 10 00:01:04,769 --> 00:01:05,910 Yes, we can. 11 00:01:05,940 --> 00:01:08,280 Can we ping ten 1 to 1? 12 00:01:08,310 --> 00:01:09,510 Yes, we can. 13 00:01:09,690 --> 00:01:11,670 So we can ping this address. 14 00:01:11,700 --> 00:01:12,810 Can we ping ten? 15 00:01:12,810 --> 00:01:14,160 One, two, two. 16 00:01:14,540 --> 00:01:15,750 No, we can't. 17 00:01:15,990 --> 00:01:19,920 So we can't ping this IP address in our network. 18 00:01:20,760 --> 00:01:24,900 We are also not learning about the loopback of router four. 19 00:01:24,990 --> 00:01:33,330 So if we did do a trace, the traffic would simply be dropped by the local router, rather one because 20 00:01:33,330 --> 00:01:35,760 it doesn't know where to send the traffic. 21 00:01:36,600 --> 00:01:45,840 So again, show IP route shows us that we are only learning about this network and this network we can 22 00:01:45,840 --> 00:01:48,120 ping up to here, but we can't ping. 23 00:01:48,120 --> 00:01:49,200 Router three. 24 00:01:50,970 --> 00:01:55,800 So let's have a look at rather to show ip ospf neighbor. 25 00:01:56,100 --> 00:01:59,130 Now here we've only got one neighbor relationship. 26 00:01:59,490 --> 00:02:07,560 We've got a neighbor relationship to router one router one has this loopback address configured. 27 00:02:08,220 --> 00:02:12,360 Router two has a neighbor relationship on gigabit or zero zero. 28 00:02:12,360 --> 00:02:13,710 Slash is zero. 29 00:02:14,600 --> 00:02:20,450 Two Errata with us errata ID and the IP address show IP route. 30 00:02:21,560 --> 00:02:24,620 We are learning about the loopback of router one. 31 00:02:25,010 --> 00:02:32,300 Router two can ping the loopback of router one but is not forming a neighbor. 32 00:02:32,300 --> 00:02:34,190 Relationships with router three. 33 00:02:35,030 --> 00:02:42,740 Has rotted to got OSPF configured and enabled on gigabit 001. 34 00:02:43,100 --> 00:02:48,950 Show IP OSPF interface will show us that and the answer is yes. 35 00:02:49,430 --> 00:02:55,160 OSPF is enabled on this interface in area zero. 36 00:02:56,300 --> 00:02:59,720 Can this rather ping rather three? 37 00:02:59,810 --> 00:03:01,040 Yes, it can. 38 00:03:01,220 --> 00:03:08,720 So we have IP connectivity between router two and router three, but rather two is not forming a neighbor 39 00:03:08,720 --> 00:03:17,210 relationship with a router three even though OSPF is enabled on this network. 40 00:03:17,420 --> 00:03:19,940 In other words, on this interface. 41 00:03:20,390 --> 00:03:25,220 So why is no neighbor relationship formed to router three? 42 00:03:27,460 --> 00:03:29,920 So in rota three show IP protocols. 43 00:03:30,860 --> 00:03:33,980 Can you see the problem based on the output? 44 00:03:35,790 --> 00:03:39,660 Pause the video now if you need more time. 45 00:03:41,370 --> 00:03:41,880 Okay. 46 00:03:41,880 --> 00:03:44,730 So have a look at the networks. 47 00:03:45,510 --> 00:03:47,040 Can you see the problem? 48 00:03:47,070 --> 00:03:49,770 Here's another hint to show IP OSPF interface. 49 00:03:50,760 --> 00:03:59,240 Notice OSPF is only enabled on the loopback interface and gigabit is zero zero. 50 00:03:59,940 --> 00:04:05,940 OSPF is not enabled on gigabit or 0/1 show IP protocols. 51 00:04:05,970 --> 00:04:09,900 Why is it not running on this interface? 52 00:04:10,080 --> 00:04:21,450 Have a look at these network commands and if we do a show run pipe begin OSPF and I'll scroll up here. 53 00:04:22,200 --> 00:04:25,050 There's our router OSPF configuration. 54 00:04:25,740 --> 00:04:28,170 Notice these network commands. 55 00:04:28,740 --> 00:04:30,690 Give us a that result. 56 00:04:31,080 --> 00:04:35,850 Why is OSPF not running under this interface? 57 00:04:36,630 --> 00:04:43,050 That's because this inverse mask is looking for ten. 58 00:04:44,740 --> 00:04:45,700 Dot one. 59 00:04:46,890 --> 00:05:01,200 Dot zero anything OSPF is only going to be enabled on network ten one zero ten 130 and 3.323.3. 60 00:05:01,770 --> 00:05:05,040 But this network isn't configured on the router. 61 00:05:07,020 --> 00:05:08,970 Show IP Interface Brief. 62 00:05:09,270 --> 00:05:17,490 We have this IP address ten 13.1 ten 12.2 and 32323.3. 63 00:05:19,290 --> 00:05:22,650 We don't have network 1.1.0. 64 00:05:23,370 --> 00:05:25,680 So this command is wrong. 65 00:05:27,330 --> 00:05:31,350 So concerti rather ospf one no network. 66 00:05:31,560 --> 00:05:34,380 Ten .1.0.0. 67 00:05:37,690 --> 00:05:38,860 Area zero. 68 00:05:39,370 --> 00:05:45,760 That should be Network ten .1.3.0. 69 00:05:46,660 --> 00:05:53,620 And now that I've enabled that command notice neighbor relationships are being reset to router for. 70 00:05:55,220 --> 00:05:56,840 And that's actually incorrect. 71 00:05:56,840 --> 00:06:01,040 I should use that command network 10.1 or 2.0. 72 00:06:01,550 --> 00:06:04,790 And notice now we see a neighbor relationship to router two. 73 00:06:05,240 --> 00:06:07,340 So just to confirm, show run. 74 00:06:09,350 --> 00:06:11,270 Show ip ospf neighbor. 75 00:06:12,280 --> 00:06:14,560 We have a neighbor relationship. 76 00:06:15,070 --> 00:06:16,840 This command is incorrect. 77 00:06:17,620 --> 00:06:19,150 So let me redo that. 78 00:06:19,180 --> 00:06:20,410 That should be 79 00:06:22,540 --> 00:06:26,170 network ten 130. 80 00:06:26,440 --> 00:06:27,640 Area two. 81 00:06:29,260 --> 00:06:36,010 So be careful that you don't introduce additional problems into your network when making changes. 82 00:06:37,300 --> 00:06:40,720 Show IP OSPF neighbor that looks better. 83 00:06:40,900 --> 00:06:43,180 We have two neighbor relationships. 84 00:06:43,960 --> 00:06:45,390 Show IP route. 85 00:06:45,630 --> 00:06:46,290 Route. 86 00:06:46,570 --> 00:06:47,710 Look better. 87 00:06:48,160 --> 00:06:51,490 This router can ping the loopback of router four. 88 00:06:51,790 --> 00:06:52,150 Right. 89 00:06:52,150 --> 00:06:57,580 A two now has a neighbor relationship to router three to show ip ospf neighbor. 90 00:06:57,940 --> 00:06:59,870 The neighbor relationship is showing. 91 00:06:59,890 --> 00:07:10,570 Show ip route shows us that we've got a route to the loopback of router three and we can ping the loopback 92 00:07:10,570 --> 00:07:11,950 of router three. 93 00:07:12,820 --> 00:07:16,240 But we're not learning about network four. 94 00:07:16,990 --> 00:07:19,690 Let's check that on router three. 95 00:07:20,860 --> 00:07:31,120 The network is displayed, so I'm going to clear the OSPF process to force packet tracer to recalculate. 96 00:07:31,630 --> 00:07:34,870 Sometimes if you make a mistake like I did there. 97 00:07:37,700 --> 00:07:43,880 Packet tracer causes problems and you have to re start the OSPF process. 98 00:07:45,180 --> 00:07:46,890 So show IP rot. 99 00:07:47,580 --> 00:07:51,420 We still not learning about that neighbor relationship. 100 00:07:52,110 --> 00:07:54,660 Let's check if I introduced another problem. 101 00:07:56,300 --> 00:07:59,840 Otherwise I'll reset routers again on router three. 102 00:08:00,320 --> 00:08:01,970 But that looks good. 103 00:08:03,340 --> 00:08:09,100 We can ping the loopback of right of one and the loopback of router for. 104 00:08:10,610 --> 00:08:17,240 And rather too, we're not seeing Network four on router one. 105 00:08:17,360 --> 00:08:25,640 We're not seeing the loopback over out of four, but we can ping this IP address on router four. 106 00:08:27,680 --> 00:08:30,740 So what I'll do is reset router four. 107 00:08:32,750 --> 00:08:35,059 Clear ip ospf process. 108 00:08:36,230 --> 00:08:39,440 Let's see if that sorts out the problem. 109 00:08:39,799 --> 00:08:42,440 Show IP OSPF database. 110 00:08:43,400 --> 00:08:44,580 That looks good. 111 00:08:44,600 --> 00:08:48,450 We've got two as an area to show IP route. 112 00:08:48,470 --> 00:08:55,610 We are learning a bunch of routes and we can ping the loopback of router one on router one. 113 00:08:55,610 --> 00:08:58,940 We still not learning about the loopback of router four. 114 00:08:59,030 --> 00:09:07,250 So what I'll do on router four is re add that network sometimes in packet trace if you make a mistake 115 00:09:07,250 --> 00:09:08,480 or like I made. 116 00:09:11,360 --> 00:09:12,860 It can cause problems. 117 00:09:14,810 --> 00:09:25,430 So what I'll simply do actually is remove OSPF and then add it back again and enable OSPF on all interfaces. 118 00:09:25,700 --> 00:09:27,170 Show IP route. 119 00:09:30,040 --> 00:09:35,890 We just need to give that a bit of time and hopefully the neighbor relationship will be formed. 120 00:09:43,290 --> 00:09:44,250 That looks better.