1 00:00:02,120 --> 00:00:09,920 And then lost me the stub area flag needs to be the same the step area flag denotes whether this is 2 00:00:09,920 --> 00:00:12,870 a stub area or a normal area. 3 00:00:12,890 --> 00:00:16,780 We'll talk more about stub areas once again in later slides. 4 00:00:17,210 --> 00:00:24,480 Now let's talk about designated roads and backup designated route as in this typologies have six routers 5 00:00:24,490 --> 00:00:32,470 connected to the same Ethan that segment so soon the D6 route is connected to a switch or a hub all 6 00:00:32,470 --> 00:00:41,370 sharing the same ethernet segment designated routers or Dior's are used on broadcast multi-axis environments 7 00:00:41,460 --> 00:00:47,640 such as Ethernet and so when implementations such as non-broadcast multi-axis environments in Frame 8 00:00:47,640 --> 00:00:57,140 Relay So do explain why we have a designated Harada let's assume that this network 10 1 1 0 is connected 9 00:00:57,140 --> 00:01:00,710 to of one and the routers are connected to this. 10 00:01:00,710 --> 00:01:04,820 Ethan its segment and assume that this network goes down. 11 00:01:05,770 --> 00:01:10,460 So let's assume for the moment that there's no designated router on this Ethan that segment. 12 00:01:10,690 --> 00:01:16,960 And hopefully you'll quickly see why there is a requirement for designate Harada with to designate RATO. 13 00:01:16,980 --> 00:01:24,650 All of these routers would have a full adjacency in a full adjacency elysées are exchanged between routers. 14 00:01:24,680 --> 00:01:31,650 So in this example all one needs to notify the other routers using a links they update that there's 15 00:01:31,650 --> 00:01:39,180 been a change in the network topology or one will send an update or three send an update to our team 16 00:01:39,700 --> 00:01:49,010 2 or 4 2 or 5 or 6 notifying all of the rods that there's been a change in the typology or two when 17 00:01:49,020 --> 00:01:51,150 receiving that update from or one. 18 00:01:51,240 --> 00:01:56,560 In this case because there is no designated Rodda has a full relationship with all other routers. 19 00:01:56,760 --> 00:02:01,500 So it sends an update to all of its neighbors to notify them that there's a problem. 20 00:02:01,560 --> 00:02:07,740 The same will happen on our three or three receive an update from our one so it notifies all of its 21 00:02:07,740 --> 00:02:14,320 neighbors that there's been a change in that apology or we'll do the same thing it received an update 22 00:02:14,320 --> 00:02:15,630 from or one. 23 00:02:15,910 --> 00:02:21,130 So it sends an update to all of its neighbors and I'm sure you're getting the picture now or five received 24 00:02:21,130 --> 00:02:22,430 that update from our one. 25 00:02:22,450 --> 00:02:29,200 So it sends an update to all of its neighbors and lawlessly or six sends an update to all of its neighbors. 26 00:02:29,230 --> 00:02:36,540 So there's a lot of duplicate traffic when a single network goes down and these six routers have a full 27 00:02:36,780 --> 00:02:38,630 adjacency with one another. 28 00:02:39,000 --> 00:02:45,150 So rather than doing that a designated route is selected on the specific segment. 29 00:02:45,150 --> 00:02:53,280 So let's assume that or two was elected as a designated Rodda designated route is selected on two criteria. 30 00:02:53,370 --> 00:02:55,720 The first one is highest priority. 31 00:02:55,890 --> 00:03:03,510 You can specify the priority on an interface the default priority is 1 0 excludes Arado from becoming 32 00:03:03,510 --> 00:03:10,150 a designated Rodda or backup designate Harada the values for the priority are from 1 to 255. 33 00:03:10,200 --> 00:03:15,690 So the first criteria is high priority if the priorities are the same then the Rotto with the highest 34 00:03:15,690 --> 00:03:20,460 Rodda ID is elected as the designated route for that segment. 35 00:03:20,460 --> 00:03:23,970 So in this example we've elected or to use the designated route. 36 00:03:24,340 --> 00:03:28,310 And let's assume again that this network goes down. 37 00:03:28,380 --> 00:03:35,620 But what happens now is or one sends an update only to the designated rodders designate or out as a 38 00:03:35,630 --> 00:03:42,700 listening on this multicast address 2 2 4 0 0 6 other voters are not listening to that multicast address. 39 00:03:42,700 --> 00:03:50,500 So from an IP point of view they do not receive or see that update only the designated Harada receives 40 00:03:50,700 --> 00:03:53,290 that multicast update. 41 00:03:53,310 --> 00:03:55,480 Now multicasting isn't covered in this course. 42 00:03:56,220 --> 00:04:02,880 But briefly this infrastructure was a hub so the roads were connected via a hub at least one that multicast 43 00:04:02,880 --> 00:04:05,400 would go to all the routers. 44 00:04:05,400 --> 00:04:10,430 However only certain routers are listening or accepting that multicast. 45 00:04:10,520 --> 00:04:14,200 So only certain routers have subscribed to that multicast. 46 00:04:14,280 --> 00:04:21,770 In this case only designate Iran are listening for and accepting multi-process to address 2 2 4 0 0 47 00:04:21,780 --> 00:04:22,880 6. 48 00:04:22,950 --> 00:04:27,240 So the other odd is at least two will drop this update. 49 00:04:27,590 --> 00:04:32,310 OSPF residing at least for now is our model will not see this update. 50 00:04:32,310 --> 00:04:39,330 On the other rodders serratus 3 4 5 and 6 from an OSPF point of view low will not receive the update 51 00:04:39,750 --> 00:04:44,140 on the router to will receive the update so logically what happens. 52 00:04:44,140 --> 00:04:49,960 The link goes down Route 1 is updating Rodek to the designated router by sending a multicast to the 53 00:04:50,050 --> 00:04:57,070 address on the router to the designated routers receiving the multicast router to then sends an update 54 00:04:57,130 --> 00:05:02,170 to all the other riders on this multicast address to do for the 0 0 5. 55 00:05:02,470 --> 00:05:09,370 All OSPF routers are listening to this multicast address so they will receive the update Router one 56 00:05:09,430 --> 00:05:10,500 would receive the update. 57 00:05:10,510 --> 00:05:15,220 They wouldn't process it because it's always typologies tables are already up to date. 58 00:05:15,250 --> 00:05:21,370 So logically what happens is the update goes from one or two parties sends an update to all the other 59 00:05:21,370 --> 00:05:22,290 routers. 60 00:05:22,540 --> 00:05:28,210 They process the update and they feel that apology database is updated with the new information that 61 00:05:28,210 --> 00:05:30,470 this network has gone down. 62 00:05:30,940 --> 00:05:38,230 As you can see here it's much more efficient to use a designated router than to allow full adjacencies 63 00:05:38,230 --> 00:05:43,140 between all routers and have all those duplicate updates. 64 00:05:43,180 --> 00:05:49,090 It's important to realize that only the designator outer and backup designator Rotto will have full 65 00:05:49,090 --> 00:05:52,680 relationships to all the other bodies. 66 00:05:53,170 --> 00:06:00,900 So for instance route 4 and 5 will only have a state known as Two way in two way. 67 00:06:00,940 --> 00:06:05,960 They know about each other but no updates will be exchanged between the routers. 68 00:06:05,980 --> 00:06:09,010 So in other words are 4 or 5 will not update each other. 69 00:06:09,070 --> 00:06:15,820 Neither will are five or six and so forth and so on all rodders will only update the designator outer 70 00:06:16,000 --> 00:06:22,290 and backup designated router with changes in the topology so they have a full relationship to the designated 71 00:06:22,290 --> 00:06:23,100 router. 72 00:06:23,530 --> 00:06:30,110 This allows for the saving of updates and duplicate traffic on a single segment. 73 00:06:30,290 --> 00:06:37,610 Once again it's important to realize that Rochus on the segment will only form full relationships with 74 00:06:37,610 --> 00:06:40,580 designator routers and backup designator outhe's. 75 00:06:40,580 --> 00:06:42,830 Now in this example I've only got a designated router. 76 00:06:43,000 --> 00:06:48,860 The issue with only having a designated router is that if this router goes down updates will not be 77 00:06:48,860 --> 00:06:50,480 sent and received properly. 78 00:06:50,480 --> 00:06:56,990 So on a segment a designated router will be elected and normally a backup designator auto would also 79 00:06:56,990 --> 00:06:57,930 be elected. 80 00:06:58,250 --> 00:07:05,510 So you'd have both a designated router and backup designator outta the BBR will become the Diyar if 81 00:07:05,510 --> 00:07:06,840 the deal fails.