1
00:00:00,000 --> 00:00:07,880

2
00:00:07,880 --> 00:00:11,270
So let's jump in and get
started by configuring

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00:00:11,270 --> 00:00:17,190
IS-IS, which is our core IGP
to support segment routing.

4
00:00:17,190 --> 00:00:21,140
Now, we already have IS-IS
set up and configured,

5
00:00:21,140 --> 00:00:23,990
and we will spend a little
bit of time exploring

6
00:00:23,990 --> 00:00:27,680
that environment so we can see
what's happening by default

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00:00:27,680 --> 00:00:30,620
on our different platforms
before we jump in

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00:00:30,620 --> 00:00:33,170
and actually start
configuring segment routing.

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00:00:33,170 --> 00:00:35,180
But then, of course,
the main focus

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00:00:35,180 --> 00:00:39,390
here is going to be to configure
IS-IS for segment routing.

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00:00:39,390 --> 00:00:43,340
Now, if your environment
uses OSPF, don't worry,

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00:00:43,340 --> 00:00:47,370
we're going to do OSPF at the
end of this section as well.

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00:00:47,370 --> 00:00:49,640
But we're going to
start with IS-IS.

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00:00:49,640 --> 00:00:51,630
So let's go ahead
and get started.

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00:00:51,630 --> 00:00:53,550
We'll bring up
our topology first

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00:00:53,550 --> 00:00:55,430
so we know which
topology we're using

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00:00:55,430 --> 00:00:57,590
and how things are
set up and laid out.

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00:00:57,590 --> 00:00:59,450
And then we'll jump
into that command line,

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00:00:59,450 --> 00:01:05,150
and we'll get IS-IS configured
for segment routing.

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00:01:05,150 --> 00:01:09,850
So for this skill, we're going
to be back on MPLS topology 1.

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00:01:09,850 --> 00:01:13,070
And we're going to be
focusing on, of course,

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00:01:13,070 --> 00:01:16,120
the core of our
network, but understand

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00:01:16,120 --> 00:01:19,840
that all of the devices
are running IS-IS.

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00:01:19,840 --> 00:01:22,900
So we'll be doing a lot
of testing, for example,

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00:01:22,900 --> 00:01:28,780
from router 6 to router 5's
loopback so we can see what

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00:01:28,780 --> 00:01:30,860
the labels are doing And so on.

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00:01:30,860 --> 00:01:33,340
So even though
all of the devices

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00:01:33,340 --> 00:01:36,100
are going to be
running IS-IS and then,

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00:01:36,100 --> 00:01:41,290
later, OSPF, it is still only
the devices here in our core

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00:01:41,290 --> 00:01:44,560
that are actually
running MPLS and will

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00:01:44,560 --> 00:01:46,220
be doing segment routing.

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00:01:46,220 --> 00:01:50,470
So that said, let's go ahead
and jump into the command line.

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00:01:50,470 --> 00:01:53,530
Like I said, we'll start
by doing some observations

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00:01:53,530 --> 00:01:58,120
about what's currently
going on in the environment.

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00:01:58,120 --> 00:02:00,960
So let's start here
on router 6 by tracing

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00:02:00,960 --> 00:02:02,580
to router 5's loopback.

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00:02:02,580 --> 00:02:05,680
We'll source it from our
own loopback interface.

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00:02:05,680 --> 00:02:07,470
So what we want
to observe here--

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00:02:07,470 --> 00:02:09,970
first, of course, we
have connectivity.

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00:02:09,970 --> 00:02:12,270
So this connection is working.

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00:02:12,270 --> 00:02:15,420
Then, notice on the
second hop, we're

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00:02:15,420 --> 00:02:17,640
actually using an MPLS label.

43
00:02:17,640 --> 00:02:21,540
In this particular
case, it's 24,009.

44
00:02:21,540 --> 00:02:25,650
Now, if we remember,
24,000 and up

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00:02:25,650 --> 00:02:30,120
on iOS XR, which is what
router 4 is running,

46
00:02:30,120 --> 00:02:33,280
that is part of the
dynamic label range.

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00:02:33,280 --> 00:02:39,120
So this is not using labels
from the SRGB, or the Segment

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00:02:39,120 --> 00:02:41,010
Routing Global Block.

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00:02:41,010 --> 00:02:44,600
We could verify this
on router 1 as well.

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00:02:44,600 --> 00:02:47,100
Couple of things we could look
at here-- we could do a show

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00:02:47,100 --> 00:02:49,570
MPLS forwarding table.

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00:02:49,570 --> 00:02:52,090
What we're looking for
here is, of course,

53
00:02:52,090 --> 00:02:58,060
going to the 10.5..5.5/32, we
see that it's actually doing

54
00:02:58,060 --> 00:03:04,180
equal cost multipathing, and
it's using either label 24,009

55
00:03:04,180 --> 00:03:09,160
as it goes towards router
4, out gigabit 0002,

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00:03:09,160 --> 00:03:16,450
or it's using 24,006 towards
router 3, out gigabit 0001.

57
00:03:16,450 --> 00:03:19,240
But whichever path it
takes, it does still

58
00:03:19,240 --> 00:03:23,360
have a label coming
from the dynamic range.

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00:03:23,360 --> 00:03:27,940
If we look at the show MPLS
label table detail, what

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00:03:27,940 --> 00:03:32,050
we see here is that we have many
labels in use, most of them,

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00:03:32,050 --> 00:03:36,880
aside from reserved labels,
are above the 24,000 mark.

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00:03:36,880 --> 00:03:38,110
So we have some here--

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00:03:38,110 --> 00:03:42,780
24,003, 24,004, and so on.

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00:03:42,780 --> 00:03:45,170
But notice for all
of these prefixes,

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00:03:45,170 --> 00:03:48,470
they're currently all
out of the dynamic range.

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00:03:48,470 --> 00:03:53,000
We can also verify that if we
do a show MPLS label range,

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00:03:53,000 --> 00:03:56,900
we can see here that the
default range for dynamic labels

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00:03:56,900 --> 00:03:59,710
starts at 24,000.

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00:03:59,710 --> 00:04:04,510
So if you remember from
previous skills, on iOS XR,

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00:04:04,510 --> 00:04:10,450
the default dynamic range
for labels is 24,000 plus.

71
00:04:10,450 --> 00:04:13,030
And we can see that here
represented on the command

72
00:04:13,030 --> 00:04:13,730
line.

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00:04:13,730 --> 00:04:16,480
But if we jump over
to iOS XE, we'll

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00:04:16,480 --> 00:04:19,519
see it doesn't operate
exactly the same way.

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00:04:19,519 --> 00:04:21,820
So let's jump over to router 5.

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00:04:21,820 --> 00:04:24,700
We'll do a show MPLS
forwarding table.

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00:04:24,700 --> 00:04:27,610
Notice that all of
the local labels

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00:04:27,610 --> 00:04:32,560
here are starting at
label 16 and going up.

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00:04:32,560 --> 00:04:36,340
The outgoing labels, of course,
from the other routers, which

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00:04:36,340 --> 00:04:42,670
are all running iOS XR, are
in that 24,000 plus range.

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00:04:42,670 --> 00:04:45,940
We can, of course, verify that
with a show MPLS label range

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00:04:45,940 --> 00:04:46,760
as well.

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00:04:46,760 --> 00:04:49,840
And we see that the
downstream generic label

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00:04:49,840 --> 00:04:52,720
region, which is, essentially,
the dynamic range,

85
00:04:52,720 --> 00:04:54,640
starts at 16.

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00:04:54,640 --> 00:04:57,220
So we see that this is
the default behavior

87
00:04:57,220 --> 00:05:00,930
before we begin to
implement segment routing.

88
00:05:00,930 --> 00:05:04,430
So now that we've observed how
it acts before segment routing,

89
00:05:04,430 --> 00:05:07,610
let's go ahead and get started
with our actual configuration

90
00:05:07,610 --> 00:05:10,550
of IS-IS to support
segment routing.

91
00:05:10,550 --> 00:05:13,120
We'll just start on router 1.

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00:05:13,120 --> 00:05:15,610
So we'll go into
configuration mode

93
00:05:15,610 --> 00:05:21,670
into router IS 1, into our
address family IPv4 unicast.

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00:05:21,670 --> 00:05:24,520
And all we have to do
is configure segment

95
00:05:24,520 --> 00:05:27,040
routing for MPLS.

96
00:05:27,040 --> 00:05:31,400
We'll commit those changes,
and we'll exit configuration.

97
00:05:31,400 --> 00:05:33,880
So now that we've
done that, let's see

98
00:05:33,880 --> 00:05:38,260
if IS-IS is now using the SRGB.

99
00:05:38,260 --> 00:05:39,430
So let's do a show--

100
00:05:39,430 --> 00:05:42,310
MPLS label table detail.

101
00:05:42,310 --> 00:05:44,770
And what we're looking
for is right here,

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00:05:44,770 --> 00:05:50,470
where we see that the
label 16,000 is IS-IS.

103
00:05:50,470 --> 00:05:54,790
And notice the label block
is even listed as SRGB.

104
00:05:54,790 --> 00:05:58,270
We see that starting
label of 16,000,

105
00:05:58,270 --> 00:06:03,640
with a size of 8,000, meaning
that it will go up to 23,999.

106
00:06:03,640 --> 00:06:08,170
So here, we can see that SRGB
being implemented here and tied

107
00:06:08,170 --> 00:06:13,790
to IS-IS just by configuring
IS-IS to use segment routing.

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00:06:13,790 --> 00:06:15,730
Let's go ahead and
configure router 3.

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00:06:15,730 --> 00:06:18,800
It's the exact
same configuration.

110
00:06:18,800 --> 00:06:23,270
And we can see if we look at our
show, MPLS label table detail,

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00:06:23,270 --> 00:06:27,470
that it has assigned the
block on this router as well.

112
00:06:27,470 --> 00:06:30,120
Routers 2 and 4 will
be exactly the same,

113
00:06:30,120 --> 00:06:33,000
so this time we'll just
paste the configuration.

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00:06:33,000 --> 00:06:38,540
So there's the configuration
on router 2 and on router 4.

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00:06:38,540 --> 00:06:41,270
This, of course,
still leaves iOS XE

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00:06:41,270 --> 00:06:43,970
to configure on router 5.

117
00:06:43,970 --> 00:06:46,800
IOS XE is almost the same.

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00:06:46,800 --> 00:06:49,730
However, it does
have a requirement

119
00:06:49,730 --> 00:06:55,290
to actually enable this under
global configuration first.

120
00:06:55,290 --> 00:06:57,410
So we can see that
it's now enable

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00:06:57,410 --> 00:06:59,630
segment routing globally.

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00:06:59,630 --> 00:07:03,650
Now, what we can do is
go into router IS-IS 1.

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00:07:03,650 --> 00:07:06,170
And it's actually just
the same command here,

124
00:07:06,170 --> 00:07:09,380
we just do segment
routing MPLS again.

125
00:07:09,380 --> 00:07:11,850
And we can exit configuration.

126
00:07:11,850 --> 00:07:13,490
So if this has
been successful, we

127
00:07:13,490 --> 00:07:15,950
can do some verification
commands here.

128
00:07:15,950 --> 00:07:20,420
We'll do show segment
routing, MPLS state.

129
00:07:20,420 --> 00:07:23,030
This, of course, tells
us that it's enabled,

130
00:07:23,030 --> 00:07:26,270
much like the console message
did when we turned it on.

131
00:07:26,270 --> 00:07:30,243
We can also do GB to
see the global block.

132
00:07:30,243 --> 00:07:31,910
And here, we can see
that now that we've

133
00:07:31,910 --> 00:07:37,100
enable segment routing, the SRGB
uses those same default values,

134
00:07:37,100 --> 00:07:40,370
16,000 to 23,999.

135
00:07:40,370 --> 00:07:45,570
And now, they're actually
reserved here on iOS XE.

136
00:07:45,570 --> 00:07:48,660
If we do the show MPLS
label range again,

137
00:07:48,660 --> 00:07:51,970
notice that it didn't
change the dynamic range.

138
00:07:51,970 --> 00:07:56,130
However, it now has
a range of 16,000

139
00:07:56,130 --> 00:08:03,750
through 23,999, now permitted to
be used by IS-IS, OSPF, and BGP

140
00:08:03,750 --> 00:08:04,800
segment routing.

141
00:08:04,800 --> 00:08:09,070
But, of course, we've
only enabled IS-IS so far.

142
00:08:09,070 --> 00:08:12,850
If we look at the show IS-IS
segment routing global block,

143
00:08:12,850 --> 00:08:15,130
we can see here
that we've learned

144
00:08:15,130 --> 00:08:17,410
the global block's
being used by all

145
00:08:17,410 --> 00:08:19,340
of the other routers
in our system.

146
00:08:19,340 --> 00:08:22,750
So IS-IS is passing that
information correctly.

147
00:08:22,750 --> 00:08:25,030
And we see that
here on router 5,

148
00:08:25,030 --> 00:08:30,580
we're also using the 16,000
with a range of 8,000.

149
00:08:30,580 --> 00:08:36,470
So now, IS-IS is configured
to support segment routing.

150
00:08:36,470 --> 00:08:41,179
In this video, we took a look
at how to configure IS-IS

151
00:08:41,179 --> 00:08:45,260
to support segment routing,
which really is just a matter

152
00:08:45,260 --> 00:08:48,950
of enabling the feature
under the routing process--

153
00:08:48,950 --> 00:08:52,760
except on iOS XE, where, of
course, we have to enable it

154
00:08:52,760 --> 00:08:54,090
globally as well.

155
00:08:54,090 --> 00:08:57,170
But other than that, this is
not a very difficult process

156
00:08:57,170 --> 00:09:00,092
to configure, so this
is now up and running.

157
00:09:00,092 --> 00:09:01,800
The next thing we're
going to have to do,

158
00:09:01,800 --> 00:09:06,470
however, is configure
prefixes with prefix sids.

159
00:09:06,470 --> 00:09:10,100
Because as of right now, we're
not really putting anything

160
00:09:10,100 --> 00:09:11,390
into segment routing.

161
00:09:11,390 --> 00:09:13,740
There are no prefix sids yet.

162
00:09:13,740 --> 00:09:15,660
So that's what we're
going to do next.

163
00:09:15,660 --> 00:09:19,010
Until then, I hope this has
been informative for you,

164
00:09:19,010 --> 00:09:22,120
and I'd like to thank
you for viewing.

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00:09:22,120 --> 00:09:25,000