1
00:00:00,000 --> 00:00:07,840

2
00:00:07,840 --> 00:00:10,290
So now that our PIM
sparse mode is set up,

3
00:00:10,290 --> 00:00:14,330
it's enabled on our interfaces,
we have our RP configured,

4
00:00:14,330 --> 00:00:18,080
and we've taken a
look at IGMP, now

5
00:00:18,080 --> 00:00:20,540
let's actually
jump in and see how

6
00:00:20,540 --> 00:00:26,400
multicast operates by starting
up a source and a receiver.

7
00:00:26,400 --> 00:00:30,500
So we'll start in this
video on the receiver side,

8
00:00:30,500 --> 00:00:33,170
have it try to join
a group, and we'll

9
00:00:33,170 --> 00:00:38,660
see what happens with the star
comma G or the shared tree.

10
00:00:38,660 --> 00:00:41,180
So let's bring up our
topology, just so we

11
00:00:41,180 --> 00:00:42,600
can see what's going to happen.

12
00:00:42,600 --> 00:00:45,080
And then, of course, we'll
jump onto the command line

13
00:00:45,080 --> 00:00:47,690
and verify that everything's
working as it should

14
00:00:47,690 --> 00:00:51,370
in our multicast environment.

15
00:00:51,370 --> 00:00:54,810
So we are still on
multicast topology 1.

16
00:00:54,810 --> 00:00:59,040
And in this video, we're going
to be configuring our receiver

17
00:00:59,040 --> 00:01:06,300
over here, router 8, to
join the group to 224.1.1.1.

18
00:01:06,300 --> 00:01:10,320
This is going to cause
it to send an IGMP report

19
00:01:10,320 --> 00:01:13,170
message over to router 7.

20
00:01:13,170 --> 00:01:16,230
Then router 7 will
attempt to locate

21
00:01:16,230 --> 00:01:18,870
this group for the
receiver, and it

22
00:01:18,870 --> 00:01:24,310
will send a start comma G join
towards the rendezvous point.

23
00:01:24,310 --> 00:01:26,700
So this will go
towards router 3.

24
00:01:26,700 --> 00:01:30,600
Router 3 will then send
it over to router 4.

25
00:01:30,600 --> 00:01:33,960
So ultimately, we should
see the star comma G

26
00:01:33,960 --> 00:01:38,040
tree build from 7, to 3, to 4.

27
00:01:38,040 --> 00:01:40,860
We'll jump in and examine
that, and we'll also

28
00:01:40,860 --> 00:01:46,050
watch the IGMP messages
between router 8 and router 7.

29
00:01:46,050 --> 00:01:47,670
So let's go ahead and jump in.

30
00:01:47,670 --> 00:01:51,360
And we'll start, of course,
by setting up some debugs.

31
00:01:51,360 --> 00:01:54,780
And we'll also set up Wireshark,
so we can see this happening

32
00:01:54,780 --> 00:01:57,290
as it goes.

33
00:01:57,290 --> 00:02:00,520
So we'll begin on router 7
by turning on some debugs.

34
00:02:00,520 --> 00:02:05,680
Let's do a debug IP IGMP, so
we can see the IGMP messages.

35
00:02:05,680 --> 00:02:09,310
And we'll also do
a debug IP PIM.

36
00:02:09,310 --> 00:02:12,400
We also have a
Wireshark packet capture

37
00:02:12,400 --> 00:02:16,150
running on the gigabit
1 interface of router 8

38
00:02:16,150 --> 00:02:19,700
as well to capture
that IGMP traffic.

39
00:02:19,700 --> 00:02:23,170
So now, let's go over to router
8 and have it join our group.

40
00:02:23,170 --> 00:02:26,340

41
00:02:26,340 --> 00:02:27,960
We'll go into our
gigabit 1 interface,

42
00:02:27,960 --> 00:02:34,650
and we say IP IGMP,
join group 224.1.1.1.

43
00:02:34,650 --> 00:02:36,420
Now that we've joined
the group, let's

44
00:02:36,420 --> 00:02:39,420
go take a look at our
debugs on router 7.

45
00:02:39,420 --> 00:02:42,150
So first, let's
turn off the debugs.

46
00:02:42,150 --> 00:02:44,610
And then let's take a
look back over these

47
00:02:44,610 --> 00:02:46,750
and see what actually happened.

48
00:02:46,750 --> 00:02:49,080
So a lot of these
messages are going

49
00:02:49,080 --> 00:02:54,190
to have to do with that
default 224.0.1.40 group.

50
00:02:54,190 --> 00:02:57,610
So we need to find the
ones related to our group.

51
00:02:57,610 --> 00:03:00,930
So we see the first one
here, we have an ICMP

52
00:03:00,930 --> 00:03:05,520
received a version 2 report
on the gigabit 3 interface

53
00:03:05,520 --> 00:03:11,490
from router 8 for
the group 224.1.1.1.

54
00:03:11,490 --> 00:03:18,030
Then we see IGMP actually
adding the interface gigabit 3

55
00:03:18,030 --> 00:03:22,200
to the outbound
list for that group.

56
00:03:22,200 --> 00:03:25,080
It inserts that group
into the interface,

57
00:03:25,080 --> 00:03:28,120
and it updates the timers
and everything to make sure

58
00:03:28,120 --> 00:03:30,070
that that is a new entry.

59
00:03:30,070 --> 00:03:32,440
The next thing we
have happening here

60
00:03:32,440 --> 00:03:36,080
is we check the
RP, in other words,

61
00:03:36,080 --> 00:03:40,060
we look at the RP
map for the 10.4.4.4

62
00:03:40,060 --> 00:03:44,200
for the group 224.1.1.1.

63
00:03:44,200 --> 00:03:50,800
So now that we know that the
10.4.4.4, notice the next thing

64
00:03:50,800 --> 00:03:55,960
we do is we're now going to
build a triggered star comma G,

65
00:03:55,960 --> 00:03:58,510
either join or prune message.

66
00:03:58,510 --> 00:04:00,010
This is a generic entry.

67
00:04:00,010 --> 00:04:03,400
It doesn't tell us whether
it's a join or prune right now.

68
00:04:03,400 --> 00:04:07,930
But it's for the
group 224.1.1.1.

69
00:04:07,930 --> 00:04:10,120
We also see it
adding these entries

70
00:04:10,120 --> 00:04:12,320
into the multicast
routing table.

71
00:04:12,320 --> 00:04:13,570
And notice here.

72
00:04:13,570 --> 00:04:15,970
It's actually
sending that version

73
00:04:15,970 --> 00:04:24,040
to join or prune to 50.1.37.3,
which is its upstream RPF.

74
00:04:24,040 --> 00:04:27,700
So we can see the triggering
of the star comma G tree

75
00:04:27,700 --> 00:04:29,740
here on router 7.

76
00:04:29,740 --> 00:04:33,640
We can also see this if
we do a show IP mroute.

77
00:04:33,640 --> 00:04:40,240
Notice that we have a star
comma G entry for the 224.1.1.1.

78
00:04:40,240 --> 00:04:44,560
The RP is 10.4.4.4,
as it should be.

79
00:04:44,560 --> 00:04:47,620
The incoming
interface is gigabit 2

80
00:04:47,620 --> 00:04:50,710
with the RPF
neighbor of router 3.

81
00:04:50,710 --> 00:04:56,500
And the outgoing interface is
gigabit 3 towards router 8.

82
00:04:56,500 --> 00:05:00,130
So we can see that this star
comma G entry has been built

83
00:05:00,130 --> 00:05:02,650
properly here on router 7.

84
00:05:02,650 --> 00:05:05,830
Now we'll go ahead and
look at router 3 and 4

85
00:05:05,830 --> 00:05:06,920
in just a moment.

86
00:05:06,920 --> 00:05:11,720
But before we do that, let's go
look at the IGMP report message

87
00:05:11,720 --> 00:05:14,470
that we captured in Wireshark.

88
00:05:14,470 --> 00:05:18,640
So we are filtering
this output by IGMP.

89
00:05:18,640 --> 00:05:25,090
And what we see is that packet
66 is an IGMP version 2 report

90
00:05:25,090 --> 00:05:29,620
message for the group 224.1.1.1.

91
00:05:29,620 --> 00:05:33,530
Also notice that for the
source and destination,

92
00:05:33,530 --> 00:05:35,590
the source is of
course router 8,

93
00:05:35,590 --> 00:05:42,010
and the destination is the
group itself, 224.1.1.1.

94
00:05:42,010 --> 00:05:45,730
If we open up the
detail on this packet,

95
00:05:45,730 --> 00:05:48,460
we see under Internet
Group Management Protocol

96
00:05:48,460 --> 00:05:51,370
that again, it's IGMP version 2.

97
00:05:51,370 --> 00:05:53,470
It is a report message.

98
00:05:53,470 --> 00:05:59,140
And it is for the
multicast group 224.1.1.1.

99
00:05:59,140 --> 00:06:03,940
So this is what the IGMP report
message looks like on the wire.

100
00:06:03,940 --> 00:06:06,670
Now let's go take a look
at the rest of our tree.

101
00:06:06,670 --> 00:06:09,860
Let's jump over to router 3.

102
00:06:09,860 --> 00:06:14,510
So here on router 3, let's
do a show PIM topology.

103
00:06:14,510 --> 00:06:17,730
Notice that we have our
entry here for the star comma

104
00:06:17,730 --> 00:06:20,840
G for 224.1.1.1.

105
00:06:20,840 --> 00:06:22,830
It is in sparse mode.

106
00:06:22,830 --> 00:06:23,960
It is up.

107
00:06:23,960 --> 00:06:27,260
The is 10.4.4.4.

108
00:06:27,260 --> 00:06:31,010
We see the RPF interface
and the RPF neighbor,

109
00:06:31,010 --> 00:06:37,340
as well as the outgoing
interface is gigabit 0003,

110
00:06:37,340 --> 00:06:40,650
towards router 7,
as it should be.

111
00:06:40,650 --> 00:06:44,720
Let's go ahead and
verify this on router 4.

112
00:06:44,720 --> 00:06:47,820
Remember that since router
4 is the rendezvous point,

113
00:06:47,820 --> 00:06:50,550
this should be the
root of the tree.

114
00:06:50,550 --> 00:06:54,680
Notice on the star comma G
here on the rendezvous point,

115
00:06:54,680 --> 00:06:57,110
the RP is listed as itself.

116
00:06:57,110 --> 00:07:01,200
It has an asterisk, indicating
that that is the local router.

117
00:07:01,200 --> 00:07:04,010
It's never sent
a join to anybody

118
00:07:04,010 --> 00:07:06,080
because it doesn't need to.

119
00:07:06,080 --> 00:07:08,340
It's the root of the tree.

120
00:07:08,340 --> 00:07:13,620
Notice that the RPF check is
the de-encapsulation tunnel

121
00:07:13,620 --> 00:07:17,880
0 for 10.4.4.4.

122
00:07:17,880 --> 00:07:22,590
This would be the receiving
end of the PIM register message

123
00:07:22,590 --> 00:07:23,580
tunnel.

124
00:07:23,580 --> 00:07:26,610
Then once it gets the
information through

125
00:07:26,610 --> 00:07:31,060
the encapsulated tunnel, the
outgoing interface is gigabit

126
00:07:31,060 --> 00:07:35,790
000, which is going
over towards router 3.

127
00:07:35,790 --> 00:07:39,000
So what we see here is
that we have a star comma G

128
00:07:39,000 --> 00:07:42,780
tree starting at the
rendezvous point here,

129
00:07:42,780 --> 00:07:46,380
router 4, outgoing
interface to router 3.

130
00:07:46,380 --> 00:07:49,950
Router 3 has an outgoing
interface to router 7.

131
00:07:49,950 --> 00:07:54,310
So our star comma G tree
has built correctly.

132
00:07:54,310 --> 00:07:56,850
Now routers outside
of that path,

133
00:07:56,850 --> 00:08:00,660
say for example, router
1, at this point,

134
00:08:00,660 --> 00:08:02,910
should know nothing
about that group.

135
00:08:02,910 --> 00:08:06,360
If we do show PIM
topology, router 1

136
00:08:06,360 --> 00:08:12,480
knows about that default group
for auto RP, the 224.0.1.40,

137
00:08:12,480 --> 00:08:14,640
but it knows nothing
about the group

138
00:08:14,640 --> 00:08:20,730
that we created because it's
not on the star comma G tree.

139
00:08:20,730 --> 00:08:24,740
So in this video, we
started up a receiver,

140
00:08:24,740 --> 00:08:30,350
and that sent an IGMP message,
specifically IGMP version 2,

141
00:08:30,350 --> 00:08:33,260
to the last hop
router, which caused

142
00:08:33,260 --> 00:08:38,090
it to generate a PIM join
message for the star comma G

143
00:08:38,090 --> 00:08:41,640
tree for that group towards
the rendezvous point.

144
00:08:41,640 --> 00:08:43,850
Then we went in and
explored that tree

145
00:08:43,850 --> 00:08:47,900
to see how it was built properly
from the rendezvous point, all

146
00:08:47,900 --> 00:08:50,240
the way to that last hop router.

147
00:08:50,240 --> 00:08:52,670
Well, none of this
does us any good

148
00:08:52,670 --> 00:08:55,170
unless we actually
have a source.

149
00:08:55,170 --> 00:08:58,040
So what we're going to do
next is fire up a source

150
00:08:58,040 --> 00:09:00,810
and see how this whole
thing works together.

151
00:09:00,810 --> 00:09:04,280
Until then, I hope this has
been informative for you,

152
00:09:04,280 --> 00:09:07,390
and I'd like to thank
you for viewing.

153
00:09:07,390 --> 00:09:11,000