1 00:00:00,540 --> 00:00:07,890 They link state request requesting fool elysée information from the neighboring Rodda the neighboring 2 00:00:07,890 --> 00:00:14,940 Radi will send what's called a link State Update which is a packet that contains links state advertisements. 3 00:00:14,940 --> 00:00:19,040 And as mentioned is typically sent in response to link state request. 4 00:00:19,070 --> 00:00:24,720 This contains detailed information about the link state database rather than just an overview of it 5 00:00:25,050 --> 00:00:31,750 which was contained in the database description links that acknowledgements acknowledge or confirm receipt 6 00:00:31,810 --> 00:00:35,210 of the link state update message. 7 00:00:35,230 --> 00:00:40,890 Now an autonomous system is a grouping of rodders under communist Ministry of domain. 8 00:00:40,990 --> 00:00:47,620 So let's assume that the rod is contained within the loop portion of running OSPF within a single autonomous 9 00:00:47,620 --> 00:00:48,700 system. 10 00:00:48,760 --> 00:00:54,370 They may be connecting to other routers under another administer of domain or another company's control 11 00:00:54,580 --> 00:01:00,480 that is running rUK for example OSPF is an IGP on T-Ray gateway protocol. 12 00:01:00,640 --> 00:01:03,320 In other words it's used within an autonomous system. 13 00:01:03,670 --> 00:01:09,860 So within your organization you may have multiple routers running OSPF within the same antonymous system. 14 00:01:10,590 --> 00:01:15,000 For scalability OSPF networks are broken up into areas. 15 00:01:15,000 --> 00:01:20,970 Now there's debate about this but Cisco would recommend never more than 50 routers with a single OSPF 16 00:01:21,060 --> 00:01:21,860 area. 17 00:01:22,290 --> 00:01:27,810 In your studies in the future you may come across different figures but that's a good rule of thumb 18 00:01:27,810 --> 00:01:36,930 to use OSPF uses her Rockhill model in that you always have OSPF areas zero when you have more than 19 00:01:36,930 --> 00:01:38,430 one area. 20 00:01:38,490 --> 00:01:42,580 It is possible to run OSPF in a another area. 21 00:01:42,660 --> 00:01:46,960 Let's say Area 1 but that's only true if you have a single area. 22 00:01:47,160 --> 00:01:52,820 If you've got multiple areas you have to have Area zero which is known as the backbone area. 23 00:01:53,510 --> 00:02:01,490 All traffic from one area to area one to another area let's say Area T will traverse the backbone. 24 00:02:01,490 --> 00:02:07,760 So what you do is you break up your network into multiple areas following the physical topology with 25 00:02:07,760 --> 00:02:15,360 a view to optimize summarization and reduce routing table updates and link state advertisements. 26 00:02:15,410 --> 00:02:22,220 Certain types of LSA can be contained within an area so the flooding of elysées throughout the network 27 00:02:22,220 --> 00:02:30,290 is stopped by breaking up the network into multiple areas routers that border the backbone area and 28 00:02:30,290 --> 00:02:35,500 another area unknown area of border routers for AVR. 29 00:02:35,930 --> 00:02:43,790 The three routers highlighted here are ABRSM because they have one interface in area zero and another 30 00:02:43,790 --> 00:02:46,220 interface in another area. 31 00:02:47,300 --> 00:02:53,230 One of the advantages of AB RS is that they allow for a summarization of routes. 32 00:02:53,510 --> 00:03:01,660 If Area 1 contains Rutz 10 1 1 0 up to 10 1 100 0 and an area t. 33 00:03:01,700 --> 00:03:12,460 We have networks 10 to 1 0 up to 10 to 100 Ceara and Area 3 10 3 1 0 up to 10 3 100 0. 34 00:03:12,600 --> 00:03:16,280 Those routes can be summarized on AB rs. 35 00:03:16,320 --> 00:03:24,480 You could say these 100 Rutz will be summarized as a single wrocht on this AVR says Lesch 60 Maust is 36 00:03:24,480 --> 00:03:27,840 used to summarize these 100 drafts. 37 00:03:27,840 --> 00:03:36,900 The same could be done here 10 to 007 16 is a summary of these ruts and last 10 3 0 0 is that 16 is 38 00:03:36,900 --> 00:03:38,930 a summary of these rocks. 39 00:03:38,940 --> 00:03:43,830 This doesn't require careful planning and good IP design. 40 00:03:45,180 --> 00:03:50,610 Misrata is known as an autonomous system border Rodda for SDR. 41 00:03:50,790 --> 00:03:53,910 It borders two autonomous systems. 42 00:03:53,910 --> 00:03:59,640 In this case we've got rep on the left hand side and OSPF on the right hand side. 43 00:03:59,970 --> 00:04:06,210 Even if all of these routers including the router where within your organization this router would still 44 00:04:06,210 --> 00:04:12,960 be known as an ISP or because it's connecting one routing process up to another writing process. 45 00:04:12,990 --> 00:04:20,200 In this case OSPF So from an OSPF point of view this is an autonomous system for the router. 46 00:04:21,160 --> 00:04:29,530 The six routers all have interfaces within area zero and therefore are known as backbone routers. 47 00:04:29,940 --> 00:04:38,570 When traffic is sent from one area to another area it has to traverse the backbone to reach the destination. 48 00:04:38,940 --> 00:04:45,360 So these three Raptor's in the backbone are used to allow the traffic to flow from area one to area 49 00:04:45,390 --> 00:04:54,060 to OSPF once again requires a good design with all areas connecting to the backbone area as traffic 50 00:04:54,060 --> 00:04:58,600 flows from one area to another area through the backbone area. 51 00:04:59,790 --> 00:05:02,940 These highlighted routers are known as internal routers. 52 00:05:03,120 --> 00:05:06,580 They are internal to they specific areas. 53 00:05:07,860 --> 00:05:15,460 OSPF routers use Halo's to form neighbor relationships or adjacencies the hello protocol once again 54 00:05:15,490 --> 00:05:21,310 establishes and maintains neighbor relationships by ensuring bi directional. 55 00:05:21,310 --> 00:05:25,750 In other words two way communication between neighbors. 56 00:05:25,750 --> 00:05:32,410 Bi directional communication occurs when a router recognizes itself listed in the packet received from 57 00:05:32,410 --> 00:05:40,490 a neighbor or S. using multicast address 2 2 4 0 0 5 and contain the following information. 58 00:05:40,780 --> 00:05:47,320 Whenever relationships to be formed it's important to remember that certain parameters have to match 59 00:05:47,470 --> 00:05:49,140 on both routers. 60 00:05:49,150 --> 00:05:57,670 Now the first field contained in a hollow is the router ID a router ID identifies the specific router 61 00:05:58,150 --> 00:06:06,880 and is used in various scenarios in OSPF computing the election of a designated router or backup designated 62 00:06:06,900 --> 00:06:16,330 Rodda a router ID is chosen per router based on the highest IP address of any configuring to face when 63 00:06:16,330 --> 00:06:23,160 OSPF is enabled on the router or on the highest loopback interface active on the router. 64 00:06:23,320 --> 00:06:30,250 When OSPF is enabled or it can be manually specified using the Rodda ID command. 65 00:06:30,700 --> 00:06:38,050 So to demonstrate that you have Harada Rotto one show at the interface brief will show me the relevant 66 00:06:38,080 --> 00:06:40,020 interfaces in Misrata. 67 00:06:40,040 --> 00:06:45,490 What I'm going to do is I'm going to shut down all the interfaces and show you that OSPF is not able 68 00:06:45,490 --> 00:06:50,720 to select a router ID if the interfaces all shut down. 69 00:06:57,390 --> 00:07:06,390 So show IP interface brief again shows me that all of my interfaces are masterly shut non-global config 70 00:07:06,390 --> 00:07:17,780 mode popping the command Rodda this case OSPF and a Proteus ID will allow me to enable OSPF on this 71 00:07:17,780 --> 00:07:18,700 router. 72 00:07:19,190 --> 00:07:27,390 The process ID allows for the differentiation of multiple OSPF instances running on the same router 73 00:07:28,160 --> 00:07:34,070 that can become important in multi protocol labels switching environments or imperialis environments. 74 00:07:34,370 --> 00:07:41,210 For this cause you'll only run a single OSPF process on a router but note multiple processes can be 75 00:07:41,210 --> 00:07:44,490 enabled on erotic. 76 00:07:44,490 --> 00:07:54,770 Now notice what the Rhodes's know Rodda ID OSPF process one fail to allocate a unique Urara ID and therefore 77 00:07:54,770 --> 00:08:04,500 cannot start topping the come on do show IP protocol shows that the routing protocol in use is OSPF 78 00:08:04,600 --> 00:08:15,740 one but the Rodda ID is 0 0 0 0 OSPF is not running directly on this route it show IP interface brief 79 00:08:17,880 --> 00:08:23,190 lets enable this interface interface 00. 80 00:08:23,410 --> 00:08:25,290 No shut. 81 00:08:25,400 --> 00:08:28,110 So what L.D. is all remove Is. 82 00:08:30,310 --> 00:08:31,990 And then I'll re-enable OSPF 83 00:08:35,290 --> 00:08:48,890 notice there's no complaint to show IP protocols shows me that the Rodda ID is 10 1 1 1 to show ID to 84 00:08:48,950 --> 00:08:55,880 face brief shows me that this IP address has become the Rodda ID. 85 00:08:56,020 --> 00:09:03,700 The reason why it is the Rodda ID is chosen based on the highest IP address of any active interface. 86 00:09:03,790 --> 00:09:09,430 When the writing process is enabled safe enabled for instance these two interfaces 87 00:09:20,230 --> 00:09:21,480 as follows. 88 00:09:21,610 --> 00:09:28,760 And then top the Kim on do show the interface brief. 89 00:09:29,000 --> 00:09:36,410 You'll see that these interfaces the fast Ethan interface and the two serial interfaces all up up do 90 00:09:36,410 --> 00:09:47,650 show Ickey protocols still shows that the Rodda ID is 10 1 1 1 just change the encapsulation back to 91 00:09:47,650 --> 00:09:48,510 its default. 92 00:09:48,580 --> 00:09:51,970 So I still see and the interfaces come up again. 93 00:09:52,390 --> 00:09:59,950 But what I'd like to see is that the Rodda Id still remains as 10 1 1 1 and I could do that command 94 00:09:59,950 --> 00:10:03,690 again to show IP protocols. 95 00:10:03,840 --> 00:10:15,700 Notice the Rodda IDs 10 1 1 1 I can do this come on clear IP OSPF process to clear the OSPF process. 96 00:10:15,870 --> 00:10:17,480 Let's see if that makes any difference. 97 00:10:17,490 --> 00:10:25,650 So show IP protocol and as you can see the Rodda I.D. remains the same. 98 00:10:25,830 --> 00:10:32,460 But if I remove OSPF and then re-enabled OSPF 99 00:10:36,980 --> 00:10:43,290 noticed the Rodda idea has changed to 10 1 5 1. 100 00:10:43,470 --> 00:10:49,830 So what the Rodda has done is it looked for the highest IP address on any active interface. 101 00:10:49,920 --> 00:10:59,070 When OSPF was enabled this time when OSPF was enabled 10 1 5 1 was the highest IP address on any active 102 00:10:59,070 --> 00:11:00,360 physical interface. 103 00:11:00,570 --> 00:11:04,110 So it was chosen as the Rodda ID. 104 00:11:04,110 --> 00:11:07,490 Now what happens if we enable the loopback. 105 00:11:07,610 --> 00:11:11,280 You'll notice the loopback has the lowest IP address. 106 00:11:11,360 --> 00:11:20,240 One is far lower than 10 so no shut that you show IP protocol. 107 00:11:20,350 --> 00:11:29,970 You can see there ATA IDs stole 10 1 5 1 0 good again wrong ideas still 10 1 5 1. 108 00:11:30,070 --> 00:11:34,630 But if I remove OSPF and then re-enable it 109 00:11:37,680 --> 00:11:45,290 noticed serrata ID is now quadruple one. 110 00:11:45,520 --> 00:11:54,940 So the rule again OSPF route ID is chosen based on the highest IP address of any physical interface 111 00:11:54,940 --> 00:11:56,060 that is active. 112 00:11:56,380 --> 00:11:58,690 When the OSPF process is enabled. 113 00:11:59,140 --> 00:12:07,900 But if there is a loopback that is active the loopback overrides the physical interfaces and the loopback 114 00:12:07,900 --> 00:12:16,660 is used as the Rodda ID loop BAC's have the advantage that they never go down a list manually shut down. 115 00:12:16,690 --> 00:12:19,740 This has multiple advantages including stability. 116 00:12:19,960 --> 00:12:26,890 Mahratta ID was originally 10 1 1 1 and the router reloaded assuming that there were no loop checks 117 00:12:26,890 --> 00:12:31,230 enabled the Rodda ID would have changed to 10 1 5 1. 118 00:12:31,450 --> 00:12:38,470 So the Rodda ID number could have changed back the loopback ID would remain as quadruple one as long 119 00:12:38,470 --> 00:12:41,400 as there were no other loop BACS configured on this router. 120 00:12:41,620 --> 00:12:44,980 So it doesnt matter what the physical interfaces are set to. 121 00:12:45,160 --> 00:12:54,500 Its recommended to set the Rodda ID manually using this command and set it to a relevant loopback. 122 00:12:54,610 --> 00:12:59,830 In this case I'm just going to set it to some arbitrary value to show you that you can set it to 1 2 123 00:13:00,250 --> 00:13:10,570 1 6 8 1 and 1 which is not an IP address from a local wrote it to show IP protocol allows me to see 124 00:13:10,570 --> 00:13:14,790 that the to ID is 1 2 1 6 8 1 to 1. 125 00:13:14,830 --> 00:13:20,800 Now it's recommended practice to set the Rodda I.D. to one of the loot banks on your Rodda. 126 00:13:20,940 --> 00:13:23,640 So I'm going to set the Rodda I.D. to quadruple one 127 00:13:26,600 --> 00:13:35,290 as you can see yeah the Rodda IDs changed to quick ripple one the hello packet then contains the hello 128 00:13:35,380 --> 00:13:39,420 and did intervals which must be the same on both routers. 129 00:13:39,460 --> 00:13:43,600 Otherwise an adjacency or neighbor relationship will not be form. 130 00:13:43,660 --> 00:13:48,190 It then contains the list of neighbors that the router knows about. 131 00:13:48,550 --> 00:13:55,120 That's our data knows if there is two way communication because it recognizes itself in the list of 132 00:13:55,120 --> 00:14:02,080 neighbors that it receives in the hollow packet it then contains the area ID which must also match on 133 00:14:02,080 --> 00:14:03,460 both routers. 134 00:14:03,490 --> 00:14:10,670 It then contains a router property which can be used in designate a rotten backup designated Rodda elections. 135 00:14:11,020 --> 00:14:18,400 It then contains the designate Harada or D or IP address backup designate Harada or DDR IP address. 136 00:14:18,430 --> 00:14:22,960 We're going to talk more about designator rodders and backup designated routers in a moment. 137 00:14:23,380 --> 00:14:26,380 It then contains the indication password. 138 00:14:26,380 --> 00:14:32,450 Now there are various ways to set up a syndication including clear text and in the five Hession. 139 00:14:32,500 --> 00:14:34,580 We'll talk more about those later. 140 00:14:34,650 --> 00:14:40,000 The indication password needs to be the same otherwise the relationship will not be formed. 141 00:14:40,480 --> 00:14:48,010 And then Lawsie the stub area flag needs to be the same the step area flag denotes whether this is a 142 00:14:48,010 --> 00:14:50,920 stub area or a normal area. 143 00:14:50,920 --> 00:14:54,570 We'll talk more about stub areas once again in later slides.