1
00:00:00,460 --> 00:00:05,530
The BTR will become the Diyar if the deal fails.

2
00:00:05,760 --> 00:00:10,460
Designate a rod as a chosen only segment basis.

3
00:00:10,460 --> 00:00:17,460
So in this example on this Ethan it's segment or two may be chosen as the designated Rodda.

4
00:00:17,850 --> 00:00:25,290
But on this segment between our four and our seven or four may be chosen as the designated Rodda on

5
00:00:25,290 --> 00:00:29,990
a physical segment basis a designated route is chosen.

6
00:00:30,280 --> 00:00:36,440
So just because R4 is not a designator out on the segment does not mean that our form is not a designator

7
00:00:36,440 --> 00:00:43,590
out on the segment every Ethan that segment requires the election and maintenance of a designated Rodda.

8
00:00:43,980 --> 00:00:50,610
So from an update point of view if this link goes down or one is updating its designator or a using

9
00:00:50,610 --> 00:00:58,760
this multi-course it Race 2 to 4 0 0 is 6 or 2 the designated Ratta updates all of its neighbors on

10
00:00:58,760 --> 00:00:59,540
that segment.

11
00:00:59,540 --> 00:01:02,670
So are 3 or 6 or 5 and are 4.

12
00:01:02,870 --> 00:01:12,080
Get the update about the change of four floods that update 2 or 7 or 7 will then flood that update to

13
00:01:12,080 --> 00:01:15,070
any neighbors that it may have not shown in this diagram.

14
00:01:15,110 --> 00:01:18,850
The same with our 5 or 6 or 3 and so forth.

15
00:01:18,850 --> 00:01:21,090
The update will be flooded at the topology.

16
00:01:21,410 --> 00:01:27,710
Just as in this example where all four received the update from or 2 and then sends that to our 7.

17
00:01:27,760 --> 00:01:35,260
So just to sum up designated rodders or Dior's elected Firstly based on the highest priority the range

18
00:01:35,710 --> 00:01:38,270
is from 0 to 255.

19
00:01:38,440 --> 00:01:46,780
The default value is 1 0 disables the ability for this Rotto to become a designator out of backup designated

20
00:01:46,780 --> 00:01:47,400
route.

21
00:01:47,830 --> 00:01:53,670
If the priorities are the same the Rodda with the highest Rodda ID will become the designated Rodda.

22
00:01:53,950 --> 00:01:58,240
It's important to realize that preemption doesn't exist with designated route.

23
00:01:59,460 --> 00:02:06,180
So in this example it's a priority of routed to set to 10 and the priority of Route 5 was set to 5.

24
00:02:06,480 --> 00:02:10,860
And in the election took place or two would become the designated route.

25
00:02:11,250 --> 00:02:19,680
However a or two went down Route 5 would become the designated route if and for instance or 3 would

26
00:02:19,680 --> 00:02:21,950
become the backup designate Arata.

27
00:02:22,380 --> 00:02:28,410
Let's assume that the priorities of the other route is 0 6 to 1 that route 3 has the highest Rodda ID

28
00:02:28,800 --> 00:02:32,020
Sarada 3 becomes the designated Rodda.

29
00:02:32,220 --> 00:02:39,670
When our t comes back again it will not become a designated Rodda or backup designator Rodda.

30
00:02:39,690 --> 00:02:46,960
In other words it's not preemptive because R5 is already the designated Rodda and or three is the Becket

31
00:02:46,970 --> 00:02:53,770
designated Rodda or two will just accept that fact and will become known as a deal or other or brother

32
00:02:54,230 --> 00:02:56,010
depending which team you prefer.

33
00:02:56,330 --> 00:03:01,860
It will not try and preempt another election and try and become the designated Rodda.

34
00:03:02,180 --> 00:03:07,690
All other parties including our two will become the others in a typology like this.

35
00:03:08,960 --> 00:03:16,000
It spoke about the shortest path algorithm algorithm the SPF algorithm places each Rodda at the root

36
00:03:16,000 --> 00:03:23,110
of the tree and calculates the shortest path to each node using the digesters algorithm based on the

37
00:03:23,110 --> 00:03:26,800
cumulative cost that is required to reach that destination.

38
00:03:26,800 --> 00:03:33,970
So as an example if Radu one wants to get to a network behind router 2 it's going to determine the best

39
00:03:33,970 --> 00:03:39,540
route based on the cost which uses a formula 10 to the eight divided by bandwidth.

40
00:03:39,900 --> 00:03:45,050
So as an example this is a T1 link router one once is in traffic Draut too.

41
00:03:45,400 --> 00:03:52,870
Will it take this T1 link or will it use the pod via Rodda 3 using a team make and 10 make link now

42
00:03:52,870 --> 00:03:56,700
REPP using POP count would send the traffic directly to our team.

43
00:03:57,220 --> 00:04:03,800
But what would always be Ifti OSPF by default uses a reference bandwidth of 10 to the 8.

44
00:04:04,070 --> 00:04:08,650
You can change this and you need to and you've gig and 10 gig lengths.

45
00:04:09,050 --> 00:04:14,210
OSPF has been around for many years and in the early days there were no Spizz such as the 10 gig and

46
00:04:14,210 --> 00:04:15,150
so forth.

47
00:04:15,560 --> 00:04:20,490
So today if youve got a gig and 10 gig links you're going to want to change the reference bandwidth.

48
00:04:21,030 --> 00:04:23,180
But for now let's assume that we're using the default.

49
00:04:23,210 --> 00:04:28,740
So the cost of a link is 10 to the eight divided by the bandwidth in bits per second.

50
00:04:29,500 --> 00:04:35,670
A one kilobits per second equals 1000 bits per second one megabits per second is one million bits per

51
00:04:35,670 --> 00:04:40,560
second 10 megabits per second is 10 million bits per second.

52
00:04:40,590 --> 00:04:47,580
So the cost of a 10 megabits per second link is 10 to the eight divided by 10 million which gives you

53
00:04:47,580 --> 00:04:51,930
a cost of 10 using the same formula for a length.

54
00:04:51,930 --> 00:05:00,270
So for this link between our one and our t the cost is 10 to the 8 divide it by 1 5 4 4 triple 0 which

55
00:05:00,270 --> 00:05:01,870
gives you a cost of 64.

56
00:05:02,160 --> 00:05:05,750
So the cost using this link would be 64.

57
00:05:06,150 --> 00:05:14,670
The cost if the traffic was sent via our two would be as follows 10 to the 8 voted by 10 million which

58
00:05:14,670 --> 00:05:18,660
is 10 but they are two lengths of 10 meg.

59
00:05:18,660 --> 00:05:20,540
So the total cost is tweenie.

60
00:05:20,850 --> 00:05:23,640
So the cost Vaj the T1 is 64.

61
00:05:23,850 --> 00:05:31,410
But the cost via the 10 meg links is 20 OSPF is going to choose the link via R2 to send traffic 2 or

62
00:05:31,410 --> 00:05:38,690
3 because the cost is lower based on this formula tend to be divided by bandwidth.

63
00:05:39,180 --> 00:05:45,840
So the formula used for costing is 10 to the 8 divided by then with how you can change the reference

64
00:05:45,840 --> 00:05:52,740
bandwidth by using this on with in the OSPF process order cost reframes bandwidth and then specifying

65
00:05:52,740 --> 00:05:54,750
a value in megabits per second.

66
00:05:54,930 --> 00:05:56,230
The default is 100.

67
00:05:56,280 --> 00:06:01,810
In other words the reference bandwidth is 100 megabits per second 100 megabits per second has a constant

68
00:06:01,860 --> 00:06:09,060
OSPF of one if you change this to a thousand as an example a gigabit link would be seen as the reference

69
00:06:09,060 --> 00:06:09,800
bandwidth.

70
00:06:10,200 --> 00:06:15,770
Or if you change it to 100000 a hundred gig link would be used as a reference bandwidth.

71
00:06:16,110 --> 00:06:22,200
You need to do this c'mon and all routers where you have interfaces with bandwidth is greater than just

72
00:06:22,230 --> 00:06:23,550
Ethernet.

73
00:06:23,550 --> 00:06:26,550
You can also change the cost on an interface.

74
00:06:26,740 --> 00:06:32,940
So are all the then OSPF calculating the cost of the link based on the bandwidth you can set the OSPF

75
00:06:32,940 --> 00:06:38,170
cost by stopping the common IP OSPF cost and then specifying haveli.

76
00:06:38,610 --> 00:06:45,030
It's very important that the bandwidth statements on your interfaces be configured correctly because

77
00:06:45,060 --> 00:06:50,940
that's what OSPF Diem's the speed of the link to be hijo does the same thing.

78
00:06:51,060 --> 00:06:56,960
It uses bandwidth as part of the calculation when working out the shortest route to destination.