1 00:00:08,410 --> 00:00:16,970 Welcome to the blog in the video we're going to look at why specific Roths were chosen rather than others 2 00:00:17,380 --> 00:00:19,240 network running Cisco routers 3 00:00:28,980 --> 00:00:34,340 so apologies for routers running with ingenius 3. 4 00:00:34,540 --> 00:00:41,090 Let's have a look at Router one and use the Camacho IP ROFFT to view the writing table. 5 00:00:41,420 --> 00:00:44,080 So various routes have been learnt. 6 00:00:44,120 --> 00:00:51,560 The one I want to point out is the one in the writing table of Rato one this network has been added 7 00:00:51,740 --> 00:01:01,740 by E-I GOP d indicates the GOP as the routing protocol that added to the rot. 8 00:01:01,860 --> 00:01:07,210 So we've got multiple routes but this route is the one of interest. 9 00:01:07,560 --> 00:01:14,050 So we should be able to paying for that for that for that for which we can that's the loopback of Rado 10 00:01:14,050 --> 00:01:17,860 for to get to that network. 11 00:01:17,870 --> 00:01:25,180 We go via 10 1 to 2 and then 10 140. 12 00:01:25,290 --> 00:01:29,130 In other words it's going via this link. 13 00:01:29,550 --> 00:01:36,550 And then this link to get to the loopback of Route A for let's have a look at which routing protocols 14 00:01:36,550 --> 00:01:46,010 are running on the road show IP protocols shows us that is enabled we are running OSPF on all interfaces 15 00:01:46,010 --> 00:01:55,230 on the router UI job is also enabled on this router and so is up. 16 00:01:55,530 --> 00:01:59,400 So Rotto one has three routing protocols enabled. 17 00:01:59,470 --> 00:02:04,890 Now typically you won't do that in the real world but we are doing that here to prove a point. 18 00:02:04,960 --> 00:02:12,430 So let's look at the OSPF database to show IP speak a database in the OSPF database. 19 00:02:12,430 --> 00:02:16,520 We have a run of ID 4 out of four. 20 00:02:16,540 --> 00:02:20,650 In other words that ROFFT exists in the OSPF database. 21 00:02:20,650 --> 00:02:30,290 So why is OSPF not chosen for those ROFFT SPF is being used for this route. 22 00:02:30,520 --> 00:02:32,740 But it's not being used for this Schrott. 23 00:02:32,740 --> 00:02:34,250 Why is that. 24 00:02:34,300 --> 00:02:43,110 So to help troubleshoot we can use the following commands show IP OSPF interface brief OSPF is enabled 25 00:02:43,500 --> 00:02:51,240 on both interfaces of Rodda one show I.P who is a neighbor but it only has a neighbor relationship to 26 00:02:51,240 --> 00:03:04,050 broaden to show IPTA GOP neighbor young Job he only has a neighbor relationship to rodder three. 27 00:03:04,170 --> 00:03:15,660 Now in this typology I didn't enable the GOP on Rodda to router to only has OSPF enabled on rattus three 28 00:03:15,840 --> 00:03:18,900 in this typology. 29 00:03:19,040 --> 00:03:29,670 We only have enough GOP and ripp enabled but on Rodda too it is learning about the network 4.4 that 30 00:03:29,690 --> 00:03:37,810 4.4 through OSPF from Rodda for Sarada to he's able to ping that loop back. 31 00:03:38,060 --> 00:03:47,000 But on route one the network is not shown in the writing table and that's because of administrative 32 00:03:47,000 --> 00:03:54,840 distance UI GOP has an administrative distance of 90 who is has an administrative distance of 110. 33 00:03:54,860 --> 00:04:01,890 In other words if a road is such as Rato one learns about a network such as Ford or Ford for 4.4 from 34 00:04:01,910 --> 00:04:10,630 both and OSPF router and in each job the router the GOP Rodda is deemed to be more reliable. 35 00:04:10,870 --> 00:04:12,760 It's more believable. 36 00:04:12,760 --> 00:04:16,590 The lower the administrative distance the more believable a route. 37 00:04:16,990 --> 00:04:23,160 In this example I always P.F. has a higher admin distance when compared to your job. 38 00:04:24,160 --> 00:04:32,380 So to get to this network your GOP is believed because it has a lower administrative distance when compared 39 00:04:32,740 --> 00:04:34,040 to SPF. 40 00:04:34,060 --> 00:04:41,470 So for both the loop backs of rotisserie and Rodda for the GOP is used but who SPF is used for the Lubeck 41 00:04:41,470 --> 00:04:42,550 of Ratatouille. 42 00:04:43,030 --> 00:04:53,060 So let's concentrate on the network your job used at the moment so on rotas 3 this is the configuration 43 00:04:53,060 --> 00:04:54,450 of your job. 44 00:04:54,650 --> 00:05:01,940 If I shut down the link on rodders 3 so I'm going to shut down the sport. 45 00:05:01,940 --> 00:05:08,820 That means Rodda 3 will no longer advertise network for 4.4 to Tarrar one. 46 00:05:09,130 --> 00:05:10,380 What happens now. 47 00:05:11,330 --> 00:05:18,470 And what you'll notice is the entry is now replaced with an OSPF ROFFT And if we trace to quadruple 48 00:05:18,470 --> 00:05:28,920 for it's going via routed to if I know shut that link on Rodda 3 the links should come up and your GOP 49 00:05:29,070 --> 00:05:32,900 should advertise the rot once again on Route 1. 50 00:05:32,970 --> 00:05:40,800 The road is replaced with an easy GOP entry rather than an always P.F. entry because the GOP has a lower 51 00:05:41,010 --> 00:05:44,520 admin distance than I was P.F. does. 52 00:05:44,700 --> 00:05:49,010 So your GOP is chosen rather than always P.F.. 53 00:05:49,260 --> 00:05:52,360 So just to prove the point again or shut the interface. 54 00:05:52,470 --> 00:05:55,420 The interface on router 3. 55 00:05:55,640 --> 00:06:05,350 Before I did that and job he wrote was used but now and always be if route is used tracing to that loopback 56 00:06:05,930 --> 00:06:13,390 its not going via OSPF no shut the link to a Trace again. 57 00:06:13,650 --> 00:06:15,450 Still hasn't switched over yet. 58 00:06:15,660 --> 00:06:17,400 Let's try again. 59 00:06:17,400 --> 00:06:22,800 Notice it went from that to us so different path was taken. 60 00:06:22,800 --> 00:06:28,530 So because both your GOP and OSPF are advertising the same network. 61 00:06:28,810 --> 00:06:35,070 There is a conflict and only one entry can be put into the writing table because the GOP has a lower 62 00:06:35,410 --> 00:06:42,510 head minister of distance than OSPF your job he by default has an admin distance of 90 for internal. 63 00:06:42,510 --> 00:06:49,490 Your GOP rants always P.F. has an Edmund distance of 110 and because of that job he was chosen. 64 00:06:49,860 --> 00:06:54,410 I'll cover other scenarios based on this policy and separate videos. 65 00:06:54,420 --> 00:06:55,710 I hope you enjoyed the video. 66 00:06:55,980 --> 00:07:00,350 If it's been of benefit to you please like please also subscribe. 67 00:07:00,720 --> 00:07:02,190 I want to wish you all the very best.