1
00:00:00,000 --> 00:00:02,826
[AUDIO LOGO]

2
00:00:02,826 --> 00:00:08,010

3
00:00:08,010 --> 00:00:11,280
So now that our layer 3
VPN is up and running--

4
00:00:11,280 --> 00:00:14,410
we have verified that
just with a ping--

5
00:00:14,410 --> 00:00:19,500
let's take a few minutes just to
examine the routes, the labels,

6
00:00:19,500 --> 00:00:23,550
and the traffic itself as it's
passed through the environment

7
00:00:23,550 --> 00:00:27,810
just to wrap up our
understanding of how MPLS layer

8
00:00:27,810 --> 00:00:30,000
3 VPN actually works.

9
00:00:30,000 --> 00:00:32,729
We'll, of course, be
focusing on customer A

10
00:00:32,729 --> 00:00:35,700
here because, well, that's
the only one we currently

11
00:00:35,700 --> 00:00:36,900
have operational.

12
00:00:36,900 --> 00:00:38,940
So let's go ahead and
jump in and get started

13
00:00:38,940 --> 00:00:42,460
with doing some verification.

14
00:00:42,460 --> 00:00:44,190
So as we're jumping
in, we're going

15
00:00:44,190 --> 00:00:50,640
to be focusing on the path from
router 6 through to router 8.

16
00:00:50,640 --> 00:00:53,310
Now, of course, our
core is multipathing.

17
00:00:53,310 --> 00:00:57,300
So technically, this traffic
could also be going this way.

18
00:00:57,300 --> 00:00:59,372
We do have two
paths to get there.

19
00:00:59,372 --> 00:01:01,080
But this is part of
what we'll be looking

20
00:01:01,080 --> 00:01:03,400
at as we examine the traffic.

21
00:01:03,400 --> 00:01:05,980
So, again, let's go
ahead and jump in.

22
00:01:05,980 --> 00:01:09,340
Let's start by taking
a look at router 1.

23
00:01:09,340 --> 00:01:15,520
So let's start by doing a show
BGP VPNv4 unicast for the VRF

24
00:01:15,520 --> 00:01:18,700
customer A. And here,
we see all the routes

25
00:01:18,700 --> 00:01:21,985
that are in BGP for this VRF.

26
00:01:21,985 --> 00:01:23,860
Well, like I said, we're
going to be focusing

27
00:01:23,860 --> 00:01:26,140
on the path towards router 8.

28
00:01:26,140 --> 00:01:31,090
So let's take a look at some
more detail on this 10.8.8.8.

29
00:01:31,090 --> 00:01:34,900
So we'll simply add that prefix
to the end of our command.

30
00:01:34,900 --> 00:01:37,130
If we look at our entry
here, the first thing we see,

31
00:01:37,130 --> 00:01:40,960
of course, is that the
route extinguisher 100:10

32
00:01:40,960 --> 00:01:42,700
is applied to this route.

33
00:01:42,700 --> 00:01:45,020
And if we look a little
bit further down,

34
00:01:45,020 --> 00:01:48,070
we can see that
from router 5, we

35
00:01:48,070 --> 00:01:54,830
have received the label 24500
to use for this destination.

36
00:01:54,830 --> 00:01:58,430
So then if we do a show
MPLS forwarding table,

37
00:01:58,430 --> 00:02:00,640
we can see that
towards router 5,

38
00:02:00,640 --> 00:02:06,100
we're going to be using either
label 24403 going out interface

39
00:02:06,100 --> 00:02:16,180
gigabit 0002 towards router 4
or 24302 going out gigabit 0001

40
00:02:16,180 --> 00:02:17,770
towards router 3.

41
00:02:17,770 --> 00:02:21,300
So it should be doing
equal cost multipathic.

42
00:02:21,300 --> 00:02:25,420
If we do a show IP CEG
for router 5's loopback,

43
00:02:25,420 --> 00:02:27,890
we can see that that's
exactly what it's doing.

44
00:02:27,890 --> 00:02:29,500
We have two entries here.

45
00:02:29,500 --> 00:02:32,960
And both of them are
being equally used.

46
00:02:32,960 --> 00:02:34,510
Notice those same labels--

47
00:02:34,510 --> 00:02:40,342
24403 and 24302-- are
listed here as well.

48
00:02:40,342 --> 00:02:41,800
Now, if we want to
see what's going

49
00:02:41,800 --> 00:02:44,860
to happen towards the
final destination,

50
00:02:44,860 --> 00:02:47,800
we can do a show
IP CEF for the VRF

51
00:02:47,800 --> 00:02:50,330
and then put in that
destination address.

52
00:02:50,330 --> 00:02:52,630
And notice what's happening.

53
00:02:52,630 --> 00:02:56,740
As it goes to each next
hop, the forwarding label

54
00:02:56,740 --> 00:02:59,110
or the first label
is going to be

55
00:02:59,110 --> 00:03:04,060
either the 24403 or the
24302 like we just discussed.

56
00:03:04,060 --> 00:03:10,000
Then we see the 24500 being
imposed as the VPN label coming

57
00:03:10,000 --> 00:03:11,770
from router 5.

58
00:03:11,770 --> 00:03:14,980
And if we trace to this
address from router 6,

59
00:03:14,980 --> 00:03:19,580
we should see these exact
labels being implemented.

60
00:03:19,580 --> 00:03:23,500
So we'll trace to the
10.8.8.8 from our loopback 100

61
00:03:23,500 --> 00:03:24,920
interface.

62
00:03:24,920 --> 00:03:27,500
So if we take a look at
the output of this trace,

63
00:03:27,500 --> 00:03:30,310
we can see exactly
what's happening.

64
00:03:30,310 --> 00:03:34,210
First, we go to router
1 with no label.

65
00:03:34,210 --> 00:03:41,590
Router 1 then multipaths on hop
2 to go between routers and 4.

66
00:03:41,590 --> 00:03:43,630
Of course, when
going to router 4,

67
00:03:43,630 --> 00:03:46,720
it puts on the
forwarding label of 403.

68
00:03:46,720 --> 00:03:50,830
When going to router 3, it's
putting on the label 302.

69
00:03:50,830 --> 00:03:56,200
But both of them still have
the same VPN label 24500.

70
00:03:56,200 --> 00:03:59,500
Then we see that as it's
forwarded to router 5,

71
00:03:59,500 --> 00:04:04,210
it's actually doing PHP
or Penultimate Hop Popping

72
00:04:04,210 --> 00:04:07,240
and removing the
forwarding label

73
00:04:07,240 --> 00:04:11,110
but still delivering it to
router 5 with the VPN label

74
00:04:11,110 --> 00:04:13,090
24,500.

75
00:04:13,090 --> 00:04:15,070
That label is then removed.

76
00:04:15,070 --> 00:04:19,779
And the packet is delivered at
hop 4 to the destination router

77
00:04:19,779 --> 00:04:23,140
8 with no label.

78
00:04:23,140 --> 00:04:27,030
So in this video, we took a look
at the routes and the labels

79
00:04:27,030 --> 00:04:28,710
in our environment
that are being

80
00:04:28,710 --> 00:04:30,430
used to forward the traffic.

81
00:04:30,430 --> 00:04:34,050
And then we saw how those labels
are being put on that traffic

82
00:04:34,050 --> 00:04:35,790
here in our trace route.

83
00:04:35,790 --> 00:04:38,700
So hopefully, this
was a helpful exercise

84
00:04:38,700 --> 00:04:41,580
to help put all of these
pieces together as far

85
00:04:41,580 --> 00:04:44,800
as how MPLS layer 3 VPN works.

86
00:04:44,800 --> 00:04:46,920
So that concludes
everything that we

87
00:04:46,920 --> 00:04:49,590
need to cover in this
skill, leaving us

88
00:04:49,590 --> 00:04:51,220
with one more thing to do.

89
00:04:51,220 --> 00:04:54,300
And that's our review
in the form of a quiz.

90
00:04:54,300 --> 00:04:56,980
And that's exactly what
we're going to do next.

91
00:04:56,980 --> 00:05:00,150
Until then, I hope this has
been informative for you.

92
00:05:00,150 --> 00:05:03,140
And I'd like to thank
you for viewing.

93
00:05:03,140 --> 00:05:07,000