WEBVTT

1
00:00.000 --> 00:08.360
So for this challenge, we're asked to answer a few questions to prove that we

2
00:08.360 --> 00:09.280
understand

3
00:09.280 --> 00:11.800
the concepts in this skill.

4
00:11.800 --> 00:16.520
So that said, let's jump in with our first question.

5
00:16.520 --> 00:22.040
Which of the following statements about prefix lists is correct?

6
00:22.040 --> 00:25.360
So let's work our way down our list here.

7
00:25.360 --> 00:31.880
Next, prefix lists are used to filter OSPF LSAs.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

7
00:25.360 --> 00:31.880
Next, prefix lists are used to filter OSPF LSAs.

8
00:31.880 --> 00:36.720
And the big problem with this answer is right here, it's the LSAs.

9
00:36.720 --> 00:45.310
LSAs are what update the database in OSPF and we don't filter out LSAs in the O

10
00:45.310 --> 00:46.440
SPF environment

11
00:46.440 --> 00:48.960
because the databases have to match.

12
00:48.960 --> 00:52.320
So this is not going to be a correct answer.

13
00:52.320 --> 00:58.880
Next answer, prefix lists are only applicable to IPv6 addresses.

14
00:58.880 --> 01:04.190
Well we actually saw these being used for IPv4 addresses so we know that this
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

14
00:58.880 --> 01:04.190
Well we actually saw these being used for IPv4 addresses so we know that this

15
01:04.190 --> 01:05.440
is incorrect.

16
01:05.440 --> 01:10.980
Just be aware however that they are also available for IPv6 but they're

17
01:10.980 --> 01:12.560
certainly not only for

18
01:12.560 --> 01:14.680
IPv6.

19
01:14.680 --> 01:19.200
Prefix lists are used to set BGP attributes.

20
01:19.200 --> 01:25.360
Now this is sort of an interesting answer because they actually can be used to

21
01:25.360 --> 01:25.920
set BGP

22
01:25.920 --> 01:30.200
attributes in conjunction with a route map.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

22
01:25.920 --> 01:30.200
attributes in conjunction with a route map.

23
01:30.200 --> 01:35.160
But in the context of that route map, the prefix list is only used for the

24
01:35.160 --> 01:35.960
match.

25
01:35.960 --> 01:40.000
It's not used to do the actual setting of the attributes.

26
01:40.000 --> 01:44.550
So although that could be a correct answer in a certain light, it's really not

27
01:44.550 --> 01:45.160
a correct

28
01:45.160 --> 01:46.400
answer.

29
01:46.400 --> 01:50.520
So of course that would leave us with the last answer here.

30
01:50.520 --> 01:55.290
Prefix lists can be used to control the redistribution of routes between

31
01:55.290 --> 01:57.880
different routing protocols

32
01:57.880 --> 02:00.400
as our correct answer.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

32
01:57.880 --> 02:00.400
as our correct answer.

33
02:00.400 --> 02:06.530
Next question, which of the following statements about AS path filters is

34
02:06.530 --> 02:07.560
correct?

35
02:07.560 --> 02:10.360
So again let's work down our answers here.

36
02:10.360 --> 02:16.400
AS path filters are used to filter routes based on the IP prefix.

37
02:16.400 --> 02:18.600
Well this is clearly not correct.

38
02:18.600 --> 02:23.550
We just saw prefix lists which in fact are what we use to filter based on IP

39
02:23.550 --> 02:25.040
prefix lists

40
02:25.040 --> 02:28.840
but that's not what the AS path filter does.

41
02:28.840 --> 02:36.280
Next, AS path filters use regular expressions to match the AS path of incoming
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

41
02:28.840 --> 02:36.280
Next, AS path filters use regular expressions to match the AS path of incoming

42
02:36.280 --> 02:37.520
or outgoing

43
02:37.520 --> 02:39.600
BGP routes.

44
02:39.600 --> 02:41.880
Now that sounds like a really good answer.

45
02:41.880 --> 02:47.040
I'm leaning towards that being correct but let's verify the other answers first

46
02:47.040 --> 02:47.320
.

47
02:47.320 --> 02:53.720
AS path filters are applied only to external BGP or EBGP peers.

48
02:53.720 --> 02:54.800
Well that one's not correct.

49
02:54.800 --> 03:00.920
We can actually use it on any neighbor, be it EBGP or IBGP.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

49
02:54.800 --> 03:00.920
We can actually use it on any neighbor, be it EBGP or IBGP.

50
03:00.920 --> 03:03.240
So that answer's not correct.

51
03:03.240 --> 03:10.000
And finally, AS path filters are used to modify BGP attributes such as local

52
03:10.000 --> 03:11.480
preference or

53
03:11.480 --> 03:13.520
MED.

54
03:13.520 --> 03:16.760
Once again these are meant for filtering updates.

55
03:16.760 --> 03:18.720
This is not what they're for.

56
03:18.720 --> 03:23.200
Therefore the correct answer is going to be answer two here.

57
03:23.200 --> 03:29.470
AS path filters use regular expressions to match the AS path of incoming or

58
03:29.470 --> 03:31.080
outgoing BGP
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

58
03:29.470 --> 03:31.080
outgoing BGP

59
03:31.080 --> 03:32.560
routes.

60
03:32.560 --> 03:37.810
So, the question which of the following statements about route redistribution

61
03:37.810 --> 03:38.880
is correct?

62
03:38.880 --> 03:44.530
Redistribution only occurs between routing protocols of the same type such as O

63
03:44.530 --> 03:45.320
SPF to

64
03:45.320 --> 03:46.320
OSPF.

65
03:46.320 --> 03:47.920
This is absolutely not correct.

66
03:47.920 --> 03:51.760
We can redistribute between any routing protocols.

67
03:51.760 --> 03:55.460
Sometimes of course we may have to provide a seed metric but nonetheless we can

68
03:55.460 --> 03:56.200
redistribute

69
03:56.200 --> 04:00.680
between different routing protocols of different types.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

69
03:56.200 --> 04:00.680
between different routing protocols of different types.

70
04:00.680 --> 04:06.290
Next answer, route redistribution allows routing information from one protocol

71
04:06.290 --> 04:07.440
to be advertised

72
04:07.440 --> 04:13.400
into another facilitating connectivity between different routing domains.

73
04:13.400 --> 04:18.480
That sounds like a really good answer but let's verify the others first.

74
04:18.480 --> 04:23.400
Redistribution is not supported between BGP and OSPF.

75
04:23.400 --> 04:25.360
This of course is not true.

76
04:25.360 --> 04:30.280
We can absolutely redistribute between OSPF and BGP.
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

76
04:25.360 --> 04:30.280
We can absolutely redistribute between OSPF and BGP.

77
04:30.280 --> 04:35.500
Next answer, when redistributing routes into OSPF the redistributed routes

78
04:35.500 --> 04:36.280
always get a

79
04:36.280 --> 04:40.120
metric of one by default.

80
04:40.120 --> 04:42.240
This one is also going to be incorrect.

81
04:42.240 --> 04:49.200
Now keep in mind if we're redistributing from BGP this would be true.

82
04:49.200 --> 04:54.120
But again the problem with this answer is the word always.

83
04:54.120 --> 04:58.420
If we're redistributing from a different protocol such as EIGRP or RIP or

84
04:58.420 --> 05:00.240
something else,
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

84
04:58.420 --> 05:00.240
something else,

85
05:00.240 --> 05:04.320
then the default metric is actually going to be 20.

86
05:04.320 --> 05:08.520
So that actually leaves again answer number two here.

87
05:08.520 --> 05:14.080
Route redistribution allows routing information from one protocol to be

88
05:14.080 --> 05:15.520
advertised into another

89
05:15.520 --> 05:22.280
facilitating connectivity between different routing domains as our correct

90
05:22.280 --> 05:23.240
answer.

91
05:23.240 --> 05:27.960
So that concludes this challenge as well as this skill.

92
05:27.960 --> 05:31.790
So if you feel that you are missing any of the information needed to answer
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

92
05:27.960 --> 05:31.790
So if you feel that you are missing any of the information needed to answer

93
05:31.790 --> 05:32.760
these questions,

94
05:32.760 --> 05:37.620
I would encourage you to go back and review the necessary sections above in

95
05:37.620 --> 05:38.280
order to fill

96
05:38.280 --> 05:39.920
in the gaps.

97
05:39.920 --> 05:44.340
Otherwise congratulations on completing troubleshooting, filtering and

98
05:44.340 --> 05:45.560
redistribution.

99
05:45.560 --> 05:49.520
I hope this has been informative for you and I'd like to thank you for viewing.

100
05:49.520 --> 05:59.520
[BLANK_AUDIO]