1
00:00:00,000 --> 00:00:02,832
[AUDIO LOGO]

2
00:00:02,832 --> 00:00:08,039

3
00:00:08,039 --> 00:00:10,320
So the last thing we're
going to be looking at here

4
00:00:10,320 --> 00:00:13,570
is an OSPF SHAM link.

5
00:00:13,570 --> 00:00:16,379
Now, this is a
control plane tunnel

6
00:00:16,379 --> 00:00:22,110
that we can use between our
PEs to build an OSPF control

7
00:00:22,110 --> 00:00:27,210
plane to allow the routes to
come from one PE to another

8
00:00:27,210 --> 00:00:29,400
through our BGP core.

9
00:00:29,400 --> 00:00:35,370
And still come out the other
side as internal OSPF routes.

10
00:00:35,370 --> 00:00:37,770
Now, the way it's doing
that is, of course,

11
00:00:37,770 --> 00:00:40,020
building this
control plane tunnel.

12
00:00:40,020 --> 00:00:44,790
It's literally passing the OSPF
packets through the SHAM link

13
00:00:44,790 --> 00:00:50,230
and forming an actual OSPF
neighborship between the PEs.

14
00:00:50,230 --> 00:00:53,760
Now, you might be asking,
why do we need all this?

15
00:00:53,760 --> 00:00:59,010
The main reason is if our
customers have a backup link,

16
00:00:59,010 --> 00:01:03,510
so some sort of connection
outside of MPLS,

17
00:01:03,510 --> 00:01:08,410
and they want to use that as
a backup, here's the problem.

18
00:01:08,410 --> 00:01:12,300
We've seen this already
that the OSPF routes coming

19
00:01:12,300 --> 00:01:15,330
through our MPLS layer
three environment

20
00:01:15,330 --> 00:01:18,630
are coming through
as OIA routes,

21
00:01:18,630 --> 00:01:21,630
even if they're
in the same area.

22
00:01:21,630 --> 00:01:24,360
Well, the problem
is the other routers

23
00:01:24,360 --> 00:01:26,970
connecting across that
direct link, whatever

24
00:01:26,970 --> 00:01:32,430
it may be, those routes would be
coming in probably as O routes

25
00:01:32,430 --> 00:01:36,570
or just straight out
intra-area routes.

26
00:01:36,570 --> 00:01:42,300
And there's no way to have
OSPF prefer an inter-area route

27
00:01:42,300 --> 00:01:44,550
over an intra-area route.

28
00:01:44,550 --> 00:01:47,100
Which means the
customer would always

29
00:01:47,100 --> 00:01:50,650
be using that back-up link.

30
00:01:50,650 --> 00:01:54,270
They would have no way of
preferring the primary link

31
00:01:54,270 --> 00:01:55,950
going through MPLS.

32
00:01:55,950 --> 00:01:59,040
And that's what SHAM
links allow us to do.

33
00:01:59,040 --> 00:02:01,980
Now truth be told,
this is something

34
00:02:01,980 --> 00:02:03,700
we need to be familiar with.

35
00:02:03,700 --> 00:02:07,260
However, I am not really
familiar with any service

36
00:02:07,260 --> 00:02:10,620
providers that will
offer this as a service

37
00:02:10,620 --> 00:02:12,270
for their customers.

38
00:02:12,270 --> 00:02:16,050
As we go through here, I
think you'll probably see why.

39
00:02:16,050 --> 00:02:18,300
There's quite a bit
that needs to be set up.

40
00:02:18,300 --> 00:02:21,888
And all the work is on
the service provider side.

41
00:02:21,888 --> 00:02:23,430
So this is a lot of
things that we're

42
00:02:23,430 --> 00:02:27,180
going to have to configure,
set up, and get working,

43
00:02:27,180 --> 00:02:30,660
and maintain on an
ongoing basis just

44
00:02:30,660 --> 00:02:34,930
to support this one thing that
a customer may want to do.

45
00:02:34,930 --> 00:02:36,840
The better thing
to do would just

46
00:02:36,840 --> 00:02:39,810
be not to run OSPF
with that customer.

47
00:02:39,810 --> 00:02:42,330
Let them run BGP instead.

48
00:02:42,330 --> 00:02:47,730
And use normal routing admin
distances to prefer the path

49
00:02:47,730 --> 00:02:49,300
through MPLS.

50
00:02:49,300 --> 00:02:51,720
So there are other,
you could argue,

51
00:02:51,720 --> 00:02:53,800
better ways of doing this.

52
00:02:53,800 --> 00:02:56,940
However, we still want to
be familiar with SHAM links

53
00:02:56,940 --> 00:02:58,300
and how they work.

54
00:02:58,300 --> 00:03:01,200
So all of that said, let's
go ahead, and jump in,

55
00:03:01,200 --> 00:03:02,950
and take a look at SHAM links.

56
00:03:02,950 --> 00:03:04,575
Of course, we'll
start with our diagram

57
00:03:04,575 --> 00:03:06,283
so we know where we're
going to build it.

58
00:03:06,283 --> 00:03:08,130
And then we'll jump
into the command line

59
00:03:08,130 --> 00:03:11,850
and get a SHAM link
up and running.

60
00:03:11,850 --> 00:03:13,550
So for this
demonstration, we're going

61
00:03:13,550 --> 00:03:17,420
to be switching to
MPLS topology four.

62
00:03:17,420 --> 00:03:20,180
The main difference
here is we have

63
00:03:20,180 --> 00:03:24,530
this gigabit three interface
available on routers six

64
00:03:24,530 --> 00:03:28,430
and eight that we will be
using for our backup link.

65
00:03:28,430 --> 00:03:30,480
This is currently
not configured.

66
00:03:30,480 --> 00:03:33,720
So we'll be configuring
this as we go through.

67
00:03:33,720 --> 00:03:36,260
Now, the intention,
of course, is for this

68
00:03:36,260 --> 00:03:37,980
to become a backup link.

69
00:03:37,980 --> 00:03:40,890
However, as we stated
during the introduction,

70
00:03:40,890 --> 00:03:45,590
the routes learned over
this link will be O routes.

71
00:03:45,590 --> 00:03:47,750
Therefore, router
six and router eight

72
00:03:47,750 --> 00:03:49,670
is going to prefer this path.

73
00:03:49,670 --> 00:03:52,940
So our goal is
going to be to build

74
00:03:52,940 --> 00:03:58,100
a SHAM link between router
one and router five.

75
00:03:58,100 --> 00:04:02,510
So this SHAM link will allow
the routes coming through MPLS

76
00:04:02,510 --> 00:04:07,350
to also show up as O routes.

77
00:04:07,350 --> 00:04:09,750
And at that point,
we can just use

78
00:04:09,750 --> 00:04:15,746
OSPF metrics to get OSPF to
prefer the path through MPLS.

79
00:04:15,746 --> 00:04:17,579
So that's what we're
going to be setting up.

80
00:04:17,579 --> 00:04:20,175
Let's jump into the command
line and get started.

81
00:04:20,175 --> 00:04:23,640

82
00:04:23,640 --> 00:04:27,050
So let's just start by looking
at the current OSPF routing

83
00:04:27,050 --> 00:04:28,940
situation on router six.

84
00:04:28,940 --> 00:04:32,510
And as we see, of course,
all of the OSPF routes

85
00:04:32,510 --> 00:04:38,360
for the remote sites are learned
as OIA or inter-area routes

86
00:04:38,360 --> 00:04:40,130
through OSPF.

87
00:04:40,130 --> 00:04:42,290
So let's see what
happens when we bring up

88
00:04:42,290 --> 00:04:45,380
our backdoor or backup link.

89
00:04:45,380 --> 00:04:48,196
So simply go into
interface gigabit three.

90
00:04:48,196 --> 00:04:52,250
For the IP address, we're
going to use 192.168.68.

91
00:04:52,250 --> 00:04:54,620
And this side will be dot 6.

92
00:04:54,620 --> 00:04:55,610
We'll keep it simple.

93
00:04:55,610 --> 00:04:58,040
We'll just use a /24.

94
00:04:58,040 --> 00:05:00,290
And we'll bring
that interface up.

95
00:05:00,290 --> 00:05:03,200
That interface should be
automatically included

96
00:05:03,200 --> 00:05:08,090
in the OSPF process because of
the way we implemented OSPF.

97
00:05:08,090 --> 00:05:11,240
So now, let's do the same
thing on router eight.

98
00:05:11,240 --> 00:05:15,020
Again, we'll set the
IP address, 192.168.68.

99
00:05:15,020 --> 00:05:17,450
This side, of course, will be 8.

100
00:05:17,450 --> 00:05:19,410
We'll do a no shut.

101
00:05:19,410 --> 00:05:21,350
And if we wait just
a few seconds here,

102
00:05:21,350 --> 00:05:24,440
not only should the interface
come up, but we should also see

103
00:05:24,440 --> 00:05:25,910
OSPF come up.

104
00:05:25,910 --> 00:05:29,300
So after a few seconds
here, the OSPF neighborship

105
00:05:29,300 --> 00:05:30,750
did, in fact, come up.

106
00:05:30,750 --> 00:05:32,480
So let's go ahead
and take a look

107
00:05:32,480 --> 00:05:35,070
at that route to the other side.

108
00:05:35,070 --> 00:05:37,170
We'll do a show IP route.

109
00:05:37,170 --> 00:05:40,310
Let's look at the 10.100.1.6.

110
00:05:40,310 --> 00:05:43,580
What we see here is that
it's currently going directly

111
00:05:43,580 --> 00:05:48,750
to router six as we suspected
it would as an intra-area route

112
00:05:48,750 --> 00:05:51,530
and only a metric of two.

113
00:05:51,530 --> 00:05:54,240
So let's do the
typical OSPF thing.

114
00:05:54,240 --> 00:05:57,050
And let's crank up that
metric on the interface

115
00:05:57,050 --> 00:05:59,130
that we don't want to use.

116
00:05:59,130 --> 00:06:00,650
So we'll go back
into configuration,

117
00:06:00,650 --> 00:06:02,900
into interface gigabit three.

118
00:06:02,900 --> 00:06:07,710
And let's change that IP OSPF
cost to something really high.

119
00:06:07,710 --> 00:06:11,420
So OSPF will definitely
prefer to go through MPLS.

120
00:06:11,420 --> 00:06:14,000
And let's go ahead
configure that.

121
00:06:14,000 --> 00:06:17,910
We'll exit out, and let's
look at that route again.

122
00:06:17,910 --> 00:06:22,400
What we see here is the
metric has now raised to 1001.

123
00:06:22,400 --> 00:06:25,190
But we're still using
the intra-area route

124
00:06:25,190 --> 00:06:27,200
going to router six.

125
00:06:27,200 --> 00:06:30,470
And if we said,
show IP route OSPF,

126
00:06:30,470 --> 00:06:34,710
notice we're not
using any OIA routes.

127
00:06:34,710 --> 00:06:36,810
So we're not going
through MPLS at all.

128
00:06:36,810 --> 00:06:38,780
In fact, if you look
at the interfaces,

129
00:06:38,780 --> 00:06:43,830
we're only using gigabit two and
gigabit three for our routing.

130
00:06:43,830 --> 00:06:46,800
Which means we're going
right around MPLS.

131
00:06:46,800 --> 00:06:49,380
So as we said during
the introduction,

132
00:06:49,380 --> 00:06:52,940
if we want to do this
through MPLS using

133
00:06:52,940 --> 00:06:55,700
this circuit as a
backup, we're going

134
00:06:55,700 --> 00:06:57,560
to have to create a SHAM link.

135
00:06:57,560 --> 00:07:01,500
And that is built entirely on
the service provider routers.

136
00:07:01,500 --> 00:07:03,980
So let's go over to router one.

137
00:07:03,980 --> 00:07:07,040
So the first thing we'll do here
is go into configuration mode.

138
00:07:07,040 --> 00:07:09,110
We're going to need a
new loopback interface.

139
00:07:09,110 --> 00:07:11,870
Let's make this loopback 101.

140
00:07:11,870 --> 00:07:15,980
It has to be in
the customer's VRF.

141
00:07:15,980 --> 00:07:18,240
And of course, it's going
to need an IP address.

142
00:07:18,240 --> 00:07:22,760
So let's do something
like 100.100.100.101.

143
00:07:22,760 --> 00:07:25,940
And of course, we'll
make this a /32.

144
00:07:25,940 --> 00:07:26,990
We'll commit that change.

145
00:07:26,990 --> 00:07:29,060
Make sure there's no issues.

146
00:07:29,060 --> 00:07:32,750
And let's create an identical
loopback on router five.

147
00:07:32,750 --> 00:07:35,180
So on router five, we'll
just paste the configuration

148
00:07:35,180 --> 00:07:38,040
in we've seen creating a
loopback interface before.

149
00:07:38,040 --> 00:07:40,740
So there's a loopback
105 interface.

150
00:07:40,740 --> 00:07:43,640
And we can see it has a
corresponding address there

151
00:07:43,640 --> 00:07:45,440
of 105.

152
00:07:45,440 --> 00:07:48,470
Also, in the customer's VRF.

153
00:07:48,470 --> 00:07:52,830
The next thing we need to
do is bring this into BGP.

154
00:07:52,830 --> 00:07:55,250
So let's go back
over to router one.

155
00:07:55,250 --> 00:08:00,230
We'll go into router BGP
100, into the customer's VRF,

156
00:08:00,230 --> 00:08:03,170
under the address family IPv4.

157
00:08:03,170 --> 00:08:05,540
And we'll simply use the
network statement to inject

158
00:08:05,540 --> 00:08:08,840
the 100.100.100.101.

159
00:08:08,840 --> 00:08:11,040
We'll commit those changes.

160
00:08:11,040 --> 00:08:14,270
And now, we'll go bring the
loopback in on router five.

161
00:08:14,270 --> 00:08:16,430
Again, we'll just paste
in the configuration.

162
00:08:16,430 --> 00:08:19,700
We've seen this a few times,
how to inject networks.

163
00:08:19,700 --> 00:08:21,980
We'll give BGP just
a moment to converge.

164
00:08:21,980 --> 00:08:24,660
And then we'll verify
the routing table.

165
00:08:24,660 --> 00:08:28,685
So let's just do a show IP
route for the VRF customer 1A.

166
00:08:28,685 --> 00:08:31,790
And of course, what we're
looking for is this entry right

167
00:08:31,790 --> 00:08:37,700
here that we have learned the
100.100.100.101 through BGP

168
00:08:37,700 --> 00:08:39,799
in the customer's VRF.

169
00:08:39,799 --> 00:08:41,750
Let's verify on router
one as well just

170
00:08:41,750 --> 00:08:43,669
to make sure we have
the route on both sides.

171
00:08:43,669 --> 00:08:47,560

172
00:08:47,560 --> 00:08:52,620
And now, we see that we have the
100.100.100.105 here on router

173
00:08:52,620 --> 00:08:53,160
one.

174
00:08:53,160 --> 00:08:55,470
So it looks like we
have our loopbacks

175
00:08:55,470 --> 00:08:57,870
to build our SHAM link between.

176
00:08:57,870 --> 00:09:00,240
So let's go ahead and
build the SHAM link.

177
00:09:00,240 --> 00:09:04,500
This is done under the OSPF
process in the customer's VRF,

178
00:09:04,500 --> 00:09:07,740
of course, area zero.

179
00:09:07,740 --> 00:09:10,230
And we're going to build
another SHAM link between

180
00:09:10,230 --> 00:09:17,700
the 100.100.100.101 and
the 100.100.100.105.

181
00:09:17,700 --> 00:09:20,320
We'll commit those changes.

182
00:09:20,320 --> 00:09:23,600
And at this point, we should
be able to exit configuration.

183
00:09:23,600 --> 00:09:26,170
Now of course, we have to do
the same thing on router five

184
00:09:26,170 --> 00:09:28,770
before the SHAM
link will come up.

185
00:09:28,770 --> 00:09:30,630
Again, it's a similar
configuration.

186
00:09:30,630 --> 00:09:34,650
Except we have to go into the
customer-specific OSPF process.

187
00:09:34,650 --> 00:09:37,350
And then we just say,
area zero SHAM link.

188
00:09:37,350 --> 00:09:40,500
And it's still then
source and destination.

189
00:09:40,500 --> 00:09:42,570
And we can see here
on the console,

190
00:09:42,570 --> 00:09:48,450
that we've just formed an OSPF
neighborship over the OSPF SHAM

191
00:09:48,450 --> 00:09:49,710
link zero.

192
00:09:49,710 --> 00:09:52,780
So this looks like
it's working fine.

193
00:09:52,780 --> 00:09:54,870
Let's do some verification.

194
00:09:54,870 --> 00:09:58,140
Since we're here on router
five, let's just do a show

195
00:09:58,140 --> 00:10:00,570
IP OSPF SHAM links.

196
00:10:00,570 --> 00:10:03,630
We can see here that
the SHAM link is up.

197
00:10:03,630 --> 00:10:06,310
It's being run as
a demand circuit.

198
00:10:06,310 --> 00:10:08,340
Meaning, we don't
have to send hellos.

199
00:10:08,340 --> 00:10:11,070
We can actually see down
here that the adjacency state

200
00:10:11,070 --> 00:10:11,940
is full.

201
00:10:11,940 --> 00:10:15,720
And it even says,
Hello suppressed.

202
00:10:15,720 --> 00:10:17,490
So this looks like
it's up and running.

203
00:10:17,490 --> 00:10:20,580
Let's verify on
router one as well.

204
00:10:20,580 --> 00:10:22,250
Now, of course, on
router one here, it's

205
00:10:22,250 --> 00:10:23,990
already giving us
a console message

206
00:10:23,990 --> 00:10:25,500
that the neighborship is up.

207
00:10:25,500 --> 00:10:28,790
So we have pretty high
confidence that it's working.

208
00:10:28,790 --> 00:10:32,180
But just so we can see
the same command here

209
00:10:32,180 --> 00:10:37,550
it's show OSPF VRF
customer A SHAM links.

210
00:10:37,550 --> 00:10:40,040
We see the output
is almost identical.

211
00:10:40,040 --> 00:10:42,590
But we see that the SHAM
link, of course, is up.

212
00:10:42,590 --> 00:10:45,350
Once again, it's being
run as a demand circuit.

213
00:10:45,350 --> 00:10:50,270
And the adjacency state is full
with the hellos suppressed.

214
00:10:50,270 --> 00:10:52,850
So if we've done
our job correctly,

215
00:10:52,850 --> 00:10:55,850
if we go back over
to router eight now,

216
00:10:55,850 --> 00:10:58,940
and we look at this
same output again,

217
00:10:58,940 --> 00:11:03,590
yes, we have these two external
links being brought in by BGP

218
00:11:03,590 --> 00:11:05,150
through our redistribution.

219
00:11:05,150 --> 00:11:07,065
We're not going to
worry about those.

220
00:11:07,065 --> 00:11:08,690
Normally, of course,
you would probably

221
00:11:08,690 --> 00:11:10,140
want to filter those out.

222
00:11:10,140 --> 00:11:13,280
But it won't hurt anything
for the customer to see those.

223
00:11:13,280 --> 00:11:16,280
It's just not something we
would normally want to do.

224
00:11:16,280 --> 00:11:18,260
The important thing
we're here for

225
00:11:18,260 --> 00:11:23,330
is to see that, for example,
this 10.6.6.6 network is now

226
00:11:23,330 --> 00:11:26,240
going out through gigabit
one in addition to several

227
00:11:26,240 --> 00:11:27,620
of these other routes.

228
00:11:27,620 --> 00:11:30,890
Meaning, that we're now
preferring the MPLS path

229
00:11:30,890 --> 00:11:35,060
over the backup link, since we
had set that metric to 1,000.

230
00:11:35,060 --> 00:11:40,000
And we can see that these
metrics are more like four.

231
00:11:40,000 --> 00:11:44,350
So in this video, we saw
how to use an OSPF SHAM

232
00:11:44,350 --> 00:11:48,910
link to use MPLS as
our primary path,

233
00:11:48,910 --> 00:11:52,240
if we have a backup
circuit that we, well, just

234
00:11:52,240 --> 00:11:53,660
don't want to prefer.

235
00:11:53,660 --> 00:11:57,310
So as you can see, this
is quite a bit of work

236
00:11:57,310 --> 00:11:58,990
on the service provider.

237
00:11:58,990 --> 00:12:00,340
What do we have to do?

238
00:12:00,340 --> 00:12:02,680
We had to build a new
loopback and put it

239
00:12:02,680 --> 00:12:04,330
in the customer's VRF.

240
00:12:04,330 --> 00:12:08,440
We had to then advertise
that route into BGP.

241
00:12:08,440 --> 00:12:11,260
We then had to use
OSPF to build the SHAM

242
00:12:11,260 --> 00:12:13,480
link between those loopbacks.

243
00:12:13,480 --> 00:12:15,620
As I'm sure, you can
probably see here,

244
00:12:15,620 --> 00:12:17,990
this is not going to scale well.

245
00:12:17,990 --> 00:12:20,800
So again, I'm not aware
of any service providers.

246
00:12:20,800 --> 00:12:23,350
Certainly, not that
we'll do this to scale.

247
00:12:23,350 --> 00:12:26,050
Maybe, for a larger
customer, they

248
00:12:26,050 --> 00:12:28,570
might be able to get the
service provider to do it.

249
00:12:28,570 --> 00:12:32,740
But my argument there would
be, if it's a larger customer,

250
00:12:32,740 --> 00:12:35,860
they're probably already running
BGP with the service provider

251
00:12:35,860 --> 00:12:40,090
anyway, as they're
CEPE not using OSPF.

252
00:12:40,090 --> 00:12:43,510
So this would probably be
more of a small company

253
00:12:43,510 --> 00:12:46,630
or small customer
type solution anyway.

254
00:12:46,630 --> 00:12:49,390
So again, I would find
it pretty unlikely

255
00:12:49,390 --> 00:12:52,540
that you'll find these out there
too often in a service provider

256
00:12:52,540 --> 00:12:53,450
environment.

257
00:12:53,450 --> 00:12:57,070
But if you ever do, at least
now you know how they work

258
00:12:57,070 --> 00:12:58,930
and what they're for.

259
00:12:58,930 --> 00:13:01,540
That said, that
covers everything

260
00:13:01,540 --> 00:13:04,340
that we need to
cover in this skill.

261
00:13:04,340 --> 00:13:06,980
So that leaves us just
with one more thing to do.

262
00:13:06,980 --> 00:13:10,060
And that is our review
in the form of a quiz.

263
00:13:10,060 --> 00:13:12,650
And that's exactly what
we're going to do next.

264
00:13:12,650 --> 00:13:15,940
Until then, I hope this has
been informative for you.

265
00:13:15,940 --> 00:13:18,990
And I'd like to thank
you for viewing.

266
00:13:18,990 --> 00:13:22,000