1
00:00:00,000 --> 00:00:07,780

2
00:00:07,780 --> 00:00:11,590
So now we have segment routing
completely operational,

3
00:00:11,590 --> 00:00:15,790
but that's with using
ISIS as our IGP,

4
00:00:15,790 --> 00:00:18,370
and that may not be
what you're using.

5
00:00:18,370 --> 00:00:21,857
We may be using OSPF
as our core protocol.

6
00:00:21,857 --> 00:00:23,440
So now what we're
going to do is we're

7
00:00:23,440 --> 00:00:26,050
going to switch our
core over to OSPF

8
00:00:26,050 --> 00:00:30,040
and look at how the
segment routing prefixes

9
00:00:30,040 --> 00:00:34,210
are actually carried
inside the OSPF database.

10
00:00:34,210 --> 00:00:36,500
That's going to be
our main focus here.

11
00:00:36,500 --> 00:00:38,860
So let's go ahead and
bring up the topology.

12
00:00:38,860 --> 00:00:41,350
Just talk quickly about what
we're going to be changing

13
00:00:41,350 --> 00:00:44,740
and in this case more
importantly, what has already

14
00:00:44,740 --> 00:00:47,830
been configured, then we'll
jump into the command line

15
00:00:47,830 --> 00:00:50,740
and we'll get this up
and running with OSPF

16
00:00:50,740 --> 00:00:54,560
with segment routing.

17
00:00:54,560 --> 00:00:57,130
So even though we're
changing our IGP here,

18
00:00:57,130 --> 00:01:00,460
we are still on MPLS Topology 1.

19
00:01:00,460 --> 00:01:03,790
We're not changing anything
about the baseline structure.

20
00:01:03,790 --> 00:01:07,450
And also note that
all of the routers

21
00:01:07,450 --> 00:01:12,760
except router 1 and
router 5 have already

22
00:01:12,760 --> 00:01:15,460
been switched over to OSPF.

23
00:01:15,460 --> 00:01:17,950
In this particular
case, this is just

24
00:01:17,950 --> 00:01:21,730
going to be a lot of typing
and/or copying and pasting

25
00:01:21,730 --> 00:01:23,830
so rather than going
through all of that,

26
00:01:23,830 --> 00:01:26,500
we've already configured
all of the other devices.

27
00:01:26,500 --> 00:01:32,230
This way, we get to see one
iOS XR device and one iOS XE

28
00:01:32,230 --> 00:01:37,720
device, and how to convert
these from ISIS to OSPF.

29
00:01:37,720 --> 00:01:39,640
Then of course, we're
going to be focusing

30
00:01:39,640 --> 00:01:43,570
a lot on the database and how
it carries the segment routing

31
00:01:43,570 --> 00:01:44,660
information.

32
00:01:44,660 --> 00:01:48,560
So let's go ahead and jump
into our configuration.

33
00:01:48,560 --> 00:01:51,070
So since this is a
lot of configuration

34
00:01:51,070 --> 00:01:53,650
and it's really just
a bunch of typing,

35
00:01:53,650 --> 00:01:55,630
let's just talk about
the configuration

36
00:01:55,630 --> 00:01:57,490
we're going to put on
each of our devices

37
00:01:57,490 --> 00:01:59,450
and then we'll just paste it in.

38
00:01:59,450 --> 00:02:01,250
So what I have here
is on the left,

39
00:02:01,250 --> 00:02:04,580
we have the configuration for
router 1 and on the right,

40
00:02:04,580 --> 00:02:07,360
we have the configuration
for router 5,

41
00:02:07,360 --> 00:02:09,238
and we'll go through
each one of these.

42
00:02:09,238 --> 00:02:11,780
So starting with router 1, the
first thing we're going to do,

43
00:02:11,780 --> 00:02:16,250
of course, is turn off
the router ISIS process.

44
00:02:16,250 --> 00:02:21,040
We'll enable OSPF 1,
configure its router ID,

45
00:02:21,040 --> 00:02:26,950
go into the IPv4 unicast
address family, and into area 0.

46
00:02:26,950 --> 00:02:29,530
Then, of course, we get
to the first big piece

47
00:02:29,530 --> 00:02:31,840
of the configuration, which
is we're going to turn

48
00:02:31,840 --> 00:02:34,810
on segment routing MPLS.

49
00:02:34,810 --> 00:02:37,810
We then go into our
loopback 0 interface

50
00:02:37,810 --> 00:02:43,300
to assign that
prefix SID of 16,001.

51
00:02:43,300 --> 00:02:45,850
Notice that so far,
this is actually

52
00:02:45,850 --> 00:02:50,210
very similar to how
we configured ISIS.

53
00:02:50,210 --> 00:02:53,360
If you look at the rest
of this configuration,

54
00:02:53,360 --> 00:02:56,720
this is just configuring
OSPF interfaces

55
00:02:56,720 --> 00:02:59,870
to be point to point
since these are all acting

56
00:02:59,870 --> 00:03:01,950
as point to point connections.

57
00:03:01,950 --> 00:03:04,790
And if we look at the
configuration for router 5,

58
00:03:04,790 --> 00:03:07,070
it's actually very similar.

59
00:03:07,070 --> 00:03:10,970
Once again, we turn
off router ISIS 1,

60
00:03:10,970 --> 00:03:17,420
we turn on router OSPF 1, turn
on our segment routing MPLS,

61
00:03:17,420 --> 00:03:21,080
set our routing ID,
and then look at all

62
00:03:21,080 --> 00:03:22,850
the rest of these commands.

63
00:03:22,850 --> 00:03:26,000
All of these are
again, just configuring

64
00:03:26,000 --> 00:03:30,140
the interfaces to be in the
area and be point to point.

65
00:03:30,140 --> 00:03:33,480
This is all OSPF configuration
we've seen before.

66
00:03:33,480 --> 00:03:35,390
So really, the
only important part

67
00:03:35,390 --> 00:03:37,820
is the segment
routing MPLS part up

68
00:03:37,820 --> 00:03:41,010
at the top of both of
these configurations.

69
00:03:41,010 --> 00:03:43,490
So that said, let's
go ahead and paste

70
00:03:43,490 --> 00:03:46,980
each of these configurations
into the respective routers.

71
00:03:46,980 --> 00:03:49,700
Let's go over to router 1.

72
00:03:49,700 --> 00:03:52,580
So we'll paste the
config here on router 1.

73
00:03:52,580 --> 00:03:54,230
If we look through
these outputs,

74
00:03:54,230 --> 00:03:58,520
we see neighborships coming
up with router 6, router 4,

75
00:03:58,520 --> 00:03:59,810
and router 3.

76
00:03:59,810 --> 00:04:01,380
So that looks good.

77
00:04:01,380 --> 00:04:05,710
Let's go over and put the
configuration on router 5.

78
00:04:05,710 --> 00:04:08,830
We'll paste our
configuration on router 5.

79
00:04:08,830 --> 00:04:11,200
And once again, we see
neighborships coming up

80
00:04:11,200 --> 00:04:15,940
with router 8, router 9, router
10, router 4, and router 3.

81
00:04:15,940 --> 00:04:18,640
So this looks like all
of our OSPF neighborships

82
00:04:18,640 --> 00:04:19,579
have come up.

83
00:04:19,579 --> 00:04:21,550
Let's do a little
bit of verification.

84
00:04:21,550 --> 00:04:25,010
Let's do a show OSPF
neighbor detail.

85
00:04:25,010 --> 00:04:28,750
So here, we see the information
for neighbor 10 what we're

86
00:04:28,750 --> 00:04:33,700
really looking for here is where
it has the SR adjacency label.

87
00:04:33,700 --> 00:04:36,400
In this case, it's label 18.

88
00:04:36,400 --> 00:04:38,980
Down here a little further,
we see that for neighbor 9,

89
00:04:38,980 --> 00:04:41,800
it's SR adjacency label 17.

90
00:04:41,800 --> 00:04:44,110
And if we were to
continue looking down,

91
00:04:44,110 --> 00:04:47,900
each of these neighbors would
have an adjacency label.

92
00:04:47,900 --> 00:04:52,690
So we already see that OSPF is
exchanging adjacency labels.

93
00:04:52,690 --> 00:04:55,720
Let's look at a show
MPLS forwarding.

94
00:04:55,720 --> 00:05:00,970
Notice that we have not only the
adjacency labels just like we

95
00:05:00,970 --> 00:05:05,380
did in ISIS, but we also
have all of our prefix SIDs

96
00:05:05,380 --> 00:05:08,700
showing up here
exactly as they should.

97
00:05:08,700 --> 00:05:11,720
So this looks exactly
the same as it did when

98
00:05:11,720 --> 00:05:15,720
we were using ISIS as our IGP.

99
00:05:15,720 --> 00:05:17,940
The command to look at
this in the database

100
00:05:17,940 --> 00:05:25,770
is show IP OSPF database, opaque
area, type extended prefix.

101
00:05:25,770 --> 00:05:29,700
And what we're seeing here are
the type 10 opaque area link

102
00:05:29,700 --> 00:05:32,220
states for area 0.

103
00:05:32,220 --> 00:05:37,230
So notice that overall, these
are type 10 opaque LSAs.

104
00:05:37,230 --> 00:05:42,240
However, there's also an
opaque type, which in this case

105
00:05:42,240 --> 00:05:46,830
is type 7, which is
an extended prefix.

106
00:05:46,830 --> 00:05:49,650
Notice that this
particular entry happens

107
00:05:49,650 --> 00:05:52,020
to be for router 5's loopback.

108
00:05:52,020 --> 00:05:54,090
We see the prefix listed.

109
00:05:54,090 --> 00:05:57,180
We see that it's an
intra area route.

110
00:05:57,180 --> 00:05:59,460
We see that the
N-bit is actually

111
00:05:59,460 --> 00:06:03,220
set indicating that
this is also a node SID.

112
00:06:03,220 --> 00:06:05,320
Then if we scroll
down a little more,

113
00:06:05,320 --> 00:06:09,460
we have the Sub-TLV
type of prefix SID.

114
00:06:09,460 --> 00:06:14,710
We can actually see that this
is being assigned prefix SID 5.

115
00:06:14,710 --> 00:06:20,230
Of course, that's based on the
index so it would be 16,005.

116
00:06:20,230 --> 00:06:22,300
If we were to continue
to scroll down,

117
00:06:22,300 --> 00:06:24,790
all of the other entries
for the other routers

118
00:06:24,790 --> 00:06:26,620
are here in the database.

119
00:06:26,620 --> 00:06:31,240
As an example here is router
1's loopback and so on.

120
00:06:31,240 --> 00:06:32,930
They're all here.

121
00:06:32,930 --> 00:06:35,290
So now that we have all those
entries, if we do a show

122
00:06:35,290 --> 00:06:38,980
IP cef to say get to
router 1's loopback, what

123
00:06:38,980 --> 00:06:41,260
we see is whether
this traffic is going

124
00:06:41,260 --> 00:06:43,630
to router 3 or router 4 next.

125
00:06:43,630 --> 00:06:48,160
We're still using
the prefix SID 16,001

126
00:06:48,160 --> 00:06:50,710
that we received through OSPF.

127
00:06:50,710 --> 00:06:55,360
So we can see this is working
exactly as it did in ISIS.

128
00:06:55,360 --> 00:06:57,610
Let's hop over to
router 1 and take

129
00:06:57,610 --> 00:07:01,720
a look at some verification
commands on iOS XR.

130
00:07:01,720 --> 00:07:06,350
So we have essentially the same
commands on iOS XR but let's

131
00:07:06,350 --> 00:07:10,080
start here by looking at the
adjacency SIDs specifically.

132
00:07:10,080 --> 00:07:12,290
So here, we can see that
we are, in fact, learning

133
00:07:12,290 --> 00:07:16,010
the adjacency SIDs for our
different adjacent routers

134
00:07:16,010 --> 00:07:19,410
and we can look at the
extended prefixes here as well.

135
00:07:19,410 --> 00:07:23,460
We'll filter by self-originated
just to look at one entry here.

136
00:07:23,460 --> 00:07:25,280
And what we see
here is, once again,

137
00:07:25,280 --> 00:07:30,950
this is a type 10 opaque area
link state, opaque type 7,

138
00:07:30,950 --> 00:07:34,940
and then we have all the
information about our loopback

139
00:07:34,940 --> 00:07:39,000
as well as the SID index
here at the bottom.

140
00:07:39,000 --> 00:07:42,830
So we can clearly see all of
this same information being

141
00:07:42,830 --> 00:07:47,450
passed through OSPF just
like it was in ISIS.

142
00:07:47,450 --> 00:07:49,910
At the end of the day
though, none of this

143
00:07:49,910 --> 00:07:52,740
matters if our data
plane isn't working.

144
00:07:52,740 --> 00:07:55,710
So let's verify our
data plane as well.

145
00:07:55,710 --> 00:07:57,470
So we'll hop over
here to router 6

146
00:07:57,470 --> 00:07:59,870
and we'll trace to
router 5's loopback,

147
00:07:59,870 --> 00:08:02,600
sourcing it from our loopback.

148
00:08:02,600 --> 00:08:05,370
As we can see here
from our trace output,

149
00:08:05,370 --> 00:08:08,240
this is working
exactly as expected.

150
00:08:08,240 --> 00:08:12,620
At hop 2, not only are we doing
multipathing as we should be,

151
00:08:12,620 --> 00:08:15,860
but we can see that we're
using the prefix SID

152
00:08:15,860 --> 00:08:18,380
from router 5 for its loopback.

153
00:08:18,380 --> 00:08:21,680
And it's within the SRGB
so we know that we're

154
00:08:21,680 --> 00:08:23,550
doing segment routing.

155
00:08:23,550 --> 00:08:28,310
So this is working exactly
as it should with OSPF just

156
00:08:28,310 --> 00:08:31,800
like it did with ISIS.

157
00:08:31,800 --> 00:08:34,620
In this video, we
took a look at how

158
00:08:34,620 --> 00:08:37,409
segment routing works
if we change our core

159
00:08:37,409 --> 00:08:42,000
protocol from ISIS to OSPF.

160
00:08:42,000 --> 00:08:45,240
And what we found out is
all of the same information

161
00:08:45,240 --> 00:08:50,580
is carried in OSPF in
type 10 opaque LSAs

162
00:08:50,580 --> 00:08:55,470
in different opaque
types, mostly in type 7s.

163
00:08:55,470 --> 00:08:59,340
So this is completely
functional with OSPF

164
00:08:59,340 --> 00:09:02,100
as much as it is with ISIS.

165
00:09:02,100 --> 00:09:06,670
And that concludes everything we
need to discuss in this skill.

166
00:09:06,670 --> 00:09:11,160
So that leaves us with just the
review in the form of a quiz

167
00:09:11,160 --> 00:09:13,810
and that's exactly what
we're going to do next.

168
00:09:13,810 --> 00:09:17,280
Until then, I hope this has
been informative for you

169
00:09:17,280 --> 00:09:20,480
and I'd like to thank
you for viewing.

170
00:09:20,480 --> 00:09:24,000