1 00:00:12,890 --> 00:00:18,560 We've been told once again that brother one can't ping the loopback of a router. 2 00:00:18,560 --> 00:00:23,240 Four And that's true based on our ping test. 3 00:00:24,190 --> 00:00:27,700 Don't believe what you told in networking. 4 00:00:27,820 --> 00:00:29,080 Verify it. 5 00:00:29,410 --> 00:00:32,549 Show IP protocol on router one. 6 00:00:32,560 --> 00:00:40,960 Shows us that we're running OSPF with process ID one show IP route shows us that we aren't learning 7 00:00:41,140 --> 00:00:43,570 any routes through OSPF. 8 00:00:44,260 --> 00:00:52,930 Show IP ospf neighbor shows us that we do have a neighbor relationship with router two, but at the 9 00:00:52,930 --> 00:00:58,420 moment we not learning any routes we can ping router two. 10 00:00:59,020 --> 00:01:05,560 We have an OSPF relationship to router two, but we are not learning any routes. 11 00:01:06,550 --> 00:01:16,510 Let's look at rather to show IP protocols rather to is running OSPF with process ID one. 12 00:01:17,320 --> 00:01:20,260 OSPF is routing for multiple networks. 13 00:01:20,830 --> 00:01:23,080 Show IP interface brief. 14 00:01:23,860 --> 00:01:27,760 So OSPF is enabled on the loopback. 15 00:01:28,830 --> 00:01:38,640 It's enabled on gigabyte 001 and it's enabled on gigabit 000. 16 00:01:38,850 --> 00:01:41,640 Show IP ospf neighbor. 17 00:01:41,790 --> 00:01:50,520 The router has a full neighbor relationship to write a one, but there seems to be a problem with the 18 00:01:50,520 --> 00:01:56,670 neighbor relationship to the strata with this router ID and this IP address. 19 00:01:57,300 --> 00:02:01,710 So do you see a problem already in the output here? 20 00:02:02,280 --> 00:02:04,290 Show IP protocols. 21 00:02:04,950 --> 00:02:07,680 Shows us the protocol information again. 22 00:02:08,430 --> 00:02:10,289 Let's have a look at rather three. 23 00:02:11,730 --> 00:02:13,470 Let's see if this gives you another hint. 24 00:02:13,770 --> 00:02:23,220 Show IP protocols shows us that OSPF is enabled on this router, but based on this output, what's the 25 00:02:23,220 --> 00:02:24,120 problem? 26 00:02:24,720 --> 00:02:25,050 Yes. 27 00:02:25,050 --> 00:02:26,250 Another hint again. 28 00:02:27,700 --> 00:02:29,490 What's the problem? 29 00:02:29,500 --> 00:02:37,600 When you look at the output on router three show IP protocols and rather TOS show IP protocols. 30 00:02:38,050 --> 00:02:39,970 What's the problem here? 31 00:02:40,630 --> 00:02:45,520 Pause the video at this point if you need more time. 32 00:02:46,120 --> 00:02:46,420 Okay. 33 00:02:46,420 --> 00:02:52,540 So OSPF requires that every router have a unique router id. 34 00:02:53,920 --> 00:02:57,940 Notice these two routers have the same router id. 35 00:02:58,390 --> 00:03:01,900 They will not form OSPF neighbor relationships. 36 00:03:02,440 --> 00:03:09,430 If the neighboring router has the same router ID as the local router. 37 00:03:10,150 --> 00:03:17,770 The local rata router two has this router id, but it sees another neighbor with this. 38 00:03:17,770 --> 00:03:18,010 Right. 39 00:03:18,040 --> 00:03:30,190 ID rather three has the same router id and it sees that rather two is also using the same route id so 40 00:03:30,190 --> 00:03:33,310 they will not form a neighbor relationships. 41 00:03:34,490 --> 00:03:36,200 And order to show run. 42 00:03:37,100 --> 00:03:44,420 We see that OSPF is enabled on multiple interfaces, so that looks good. 43 00:03:44,540 --> 00:03:45,740 Show Run. 44 00:03:46,960 --> 00:03:54,370 Here we see that OSPF has manually been configured with a rider ID of 2.2 to 2.2. 45 00:03:55,420 --> 00:04:00,970 OSPF is enabled on individual interfaces, so that looks correct. 46 00:04:01,210 --> 00:04:03,340 But this is not correct. 47 00:04:05,140 --> 00:04:09,550 This router is forming a neighbor relationship with router four. 48 00:04:11,770 --> 00:04:18,760 And can ping the loopback of router four, but it won't form a neighbor relationship with rather two 49 00:04:18,910 --> 00:04:21,940 because it has the same router id. 50 00:04:22,690 --> 00:04:32,440 Rather to selected its rider ID based on the fact that it's got a loopback interface configured with 51 00:04:32,500 --> 00:04:33,760 this IP address. 52 00:04:34,180 --> 00:04:35,650 So that's correct. 53 00:04:35,770 --> 00:04:43,050 It chose the highest IP address of any loopback interface as its router ID here. 54 00:04:43,060 --> 00:04:45,610 The router ID was manually configured. 55 00:04:46,300 --> 00:04:48,610 So I'm going to change that. 56 00:04:50,460 --> 00:04:51,390 And say no. 57 00:04:51,390 --> 00:04:58,470 Rather ID 2.2 to 2.2 show IP protocols. 58 00:04:58,590 --> 00:05:02,520 Root ID is still configured as follows. 59 00:05:03,420 --> 00:05:14,190 So I'm going to use the command clear ip OSPF process and I'm going to clear the OSPF process to get 60 00:05:14,190 --> 00:05:17,910 it to re learn its real ID. 61 00:05:18,210 --> 00:05:20,790 So show IP protocols. 62 00:05:22,070 --> 00:05:25,850 In this example, it's still showing a rather idea of two. 63 00:05:26,330 --> 00:05:34,310 So what I'll do is manually configure a router ID of 3.3 to 3.3. 64 00:05:35,180 --> 00:05:40,780 And notice now that I've done that, the neighbor relationship comes up in packet tracer. 65 00:05:40,790 --> 00:05:48,560 You may have to manually force things and in the exam you may have to do something similar and notice 66 00:05:48,680 --> 00:06:00,230 the router ID is now 3.3 or 3.3 and that's because I manually forced it to be this in the real world. 67 00:06:00,230 --> 00:06:07,940 If you don't configure this and you reset the OSPF process, it will use the highest IP address of any 68 00:06:07,940 --> 00:06:17,330 loopback as the router ID best practice however for the real world is to manually set your router ID 69 00:06:17,360 --> 00:06:19,670 so that it won't change by mistake. 70 00:06:20,890 --> 00:06:24,040 So show ip ospf neighbor here rather. 71 00:06:24,040 --> 00:06:25,990 Relationships are good. 72 00:06:26,020 --> 00:06:30,490 Notice full and full show IP route. 73 00:06:31,000 --> 00:06:37,240 We are learning some routes through OSPF, such as the loopback address of router three. 74 00:06:37,450 --> 00:06:44,260 Hopefully we can ping the loopback address of router three, which we can on router three show IP route. 75 00:06:45,040 --> 00:06:53,650 We are learning addresses such as the loopback of right of one loopback of router two, but we can't 76 00:06:53,650 --> 00:06:58,030 ping the loopback of router four at this point. 77 00:06:58,030 --> 00:07:03,490 So we need to find out what the problem is there because. 78 00:07:06,040 --> 00:07:07,090 Rather one. 79 00:07:08,310 --> 00:07:16,740 Can stall not ping the loopback of router for it can ping the loopback of router two and router three 80 00:07:16,950 --> 00:07:23,790 but not of router four because router four loopback is not being advertised through OSPF.