1 00:00:00,630 --> 00:00:04,230 About 5 minutes ago and it executed three times. 2 00:00:05,010 --> 00:00:09,180 So let's enable OSPF on router two and see how the output changes. 3 00:00:09,840 --> 00:00:16,920 So on router to show IP interface brief will allow me to see the interfaces configured on this router. 4 00:00:17,160 --> 00:00:25,320 And as you can see here, ten one two, two has been configured on 01/0 and ten 131 has been configured 5 00:00:25,320 --> 00:00:27,300 on serial 1/1. 6 00:00:28,080 --> 00:00:30,090 Let's configure a loopback on this router. 7 00:00:30,660 --> 00:00:33,840 So interface loopback is zero ip address. 8 00:00:38,410 --> 00:00:45,880 And let's configure this quadruple t tapping the command router OSPF two will enable OSPF on this router 9 00:00:45,880 --> 00:00:51,100 with process ID two and in this case let's enable OSPF. 10 00:00:52,740 --> 00:00:54,090 Using this format. 11 00:00:56,660 --> 00:01:03,440 So obviously initially said just enable OSPF on all interfaces and let's put those interfaces in Area 12 00:01:03,440 --> 00:01:04,129 zero. 13 00:01:05,519 --> 00:01:10,440 As you can see here, a neighbor relationship or adjacency has been formed. 14 00:01:10,890 --> 00:01:19,140 Neighbor ten 151 on serial 1/0 has gone from the loading state to the full state. 15 00:01:19,800 --> 00:01:25,260 The full state means that there are those exchanging link state updates with one another. 16 00:01:25,740 --> 00:01:27,210 This can get confusing. 17 00:01:27,430 --> 00:01:32,220 Neighbor ten 151 is not directly connected to us. 18 00:01:32,700 --> 00:01:38,010 IP Address ten 151 is not directly connected to router two. 19 00:01:38,340 --> 00:01:47,310 However, that IP address is the router ID of router one and router two has formed a neighbor relationship 20 00:01:47,310 --> 00:01:56,040 with router one and thus the router ID for router one is shown in the output, not the IP address of 21 00:01:56,040 --> 00:01:57,690 serial one zero. 22 00:01:58,260 --> 00:02:04,470 By the same token, on router one notice a neighbor relationship has been formed with quadruple two 23 00:02:04,590 --> 00:02:06,750 on serial 1/0. 24 00:02:07,320 --> 00:02:10,169 Notice that the process id on router one is one. 25 00:02:11,610 --> 00:02:19,650 Whereas the process ID on router two is to process IDs are local to the writers and do not have to be 26 00:02:19,650 --> 00:02:20,340 the same. 27 00:02:21,390 --> 00:02:27,840 So I can top the command show IP OSPF interface and you can see that OSPF is enabled on the loopback 28 00:02:27,840 --> 00:02:37,230 interface serial 1/1 interface serial 1/0 interface, which are the three interfaces configured on router 29 00:02:37,230 --> 00:02:45,780 two going back to router one and topping the command show IP, OSPF will allow me to see that the SBF 30 00:02:45,780 --> 00:02:52,950 algorithm has now been executed five times because new routes have been added to the topology show. 31 00:02:52,950 --> 00:02:54,540 IP ospf. 32 00:02:55,740 --> 00:03:03,510 Neighbor will allow me to see my OSPF neighbors router one at the moment only has a neighbor relationship 33 00:03:03,510 --> 00:03:07,590 with router to notice the relationship is full. 34 00:03:07,860 --> 00:03:09,360 Notice the dash. 35 00:03:09,720 --> 00:03:14,430 The dash means that no election has taken place on this interface. 36 00:03:14,820 --> 00:03:19,890 And the reason why is that it's a point to point link on a fast Ethernet network. 37 00:03:20,160 --> 00:03:27,750 You would see various state share like D.R. for designated router, BTR for backup, designated router 38 00:03:27,990 --> 00:03:29,400 and driver. 39 00:03:29,550 --> 00:03:34,290 In other words, the neighbor is neither a D.R. or a BTR. 40 00:03:34,380 --> 00:03:41,490 It's important to realize this command show IP OSPF neighbor is giving me information about my neighbor, 41 00:03:41,490 --> 00:03:43,620 rather not about me. 42 00:03:44,250 --> 00:03:51,900 In other words, neighbor with IP address quadruple two is connected to our local serial 1/0 interface 43 00:03:52,170 --> 00:04:01,530 and the neighbors IP address on that interface is ten 122 on router to show IP OSPF neighbor. 44 00:04:02,630 --> 00:04:06,980 Will allow me to see similar information for rather one notice. 45 00:04:07,000 --> 00:04:09,710 Rather one's neighbor ID is ten 151. 46 00:04:10,040 --> 00:04:16,820 Now, as per best practice, we should be using a loopback for the right ID rather than a physical interface. 47 00:04:16,910 --> 00:04:20,899 So in router one, let's create a loopback interface. 48 00:04:28,010 --> 00:04:36,050 And top the command do show IP OSPF interface and you'll notice that the router ID has remained the 49 00:04:36,050 --> 00:04:36,650 same. 50 00:04:37,550 --> 00:04:38,960 You'll also notice. 51 00:04:40,270 --> 00:04:44,320 That the loopback interface is not in the list of interfaces. 52 00:04:44,650 --> 00:04:49,870 And the reason for that is that we only enabled OSPF on specific interfaces. 53 00:04:49,870 --> 00:04:55,090 So tapping the command do show run pipe section. 54 00:04:56,340 --> 00:05:02,430 OSPF will allow me to see the configuration of OSPF in the running configuration. 55 00:05:03,420 --> 00:05:08,970 And as you can see here, OSPF has not been enabled on the loopback interface. 56 00:05:09,750 --> 00:05:14,400 So let's type router OSPF one network. 57 00:05:15,770 --> 00:05:18,290 And let's specify a loopback address. 58 00:05:19,160 --> 00:05:20,720 Now topping the command. 59 00:05:22,220 --> 00:05:24,560 Do you show ip ospf interface? 60 00:05:25,220 --> 00:05:29,420 Shows me that my router ID is still ten 151. 61 00:05:30,910 --> 00:05:31,630 Let's type this. 62 00:05:31,630 --> 00:05:39,940 Come on, clear ip ospf process and say yes to clear all OSPF processes. 63 00:05:40,960 --> 00:05:45,070 As you can see, the neighbor relationship went down and then re-established. 64 00:05:45,850 --> 00:05:52,420 So IP OSPF interface will show me that the router ID is still ten 151. 65 00:05:52,990 --> 00:05:55,900 Now I could remove OSPF and re-enable it. 66 00:05:56,290 --> 00:06:00,010 That's a bit of a blunt instrument to change the route id. 67 00:06:00,400 --> 00:06:01,830 So I'm going to go to. 68 00:06:02,720 --> 00:06:05,210 Rada ospf one. 69 00:06:05,970 --> 00:06:11,970 Rada and then specify that Rada ID is quadruple one and notice what the Rada says. 70 00:06:12,330 --> 00:06:18,420 Either reload or use the clear IP OSPF process command for this to take effect. 71 00:06:18,990 --> 00:06:25,530 So let's type clear ip ospf process. 72 00:06:25,530 --> 00:06:29,700 Say yes to clear all processes and see what happens. 73 00:06:30,390 --> 00:06:34,110 Once again, the neighbor relationship went down and reestablished. 74 00:06:34,590 --> 00:06:43,740 Topping the command show IP OSPF interface shows me that the router ID is now set to quadruple one on 75 00:06:43,740 --> 00:06:52,230 router to show IP OSPF neighbor notice the neighbor relationship has changed to use the loopback address 76 00:06:52,230 --> 00:06:53,430 of quadruple one. 77 00:06:54,450 --> 00:07:00,330 So let's enable OSPF on router three to ensure full connectivity between all subnets. 78 00:07:02,990 --> 00:07:07,340 Show IP interface brief will allow me to see the interfaces configured on this router.