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[AUDIO LOGO]

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So now that we've configured
our other areas, in this video,

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we're going to finish up by
configuring Areas 20 and 30.

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And we're also going to look
at providing some redundancy

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to our backbone.

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As it is right now, we have
some points in our network

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where a single failure could
cause us some problems.

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So once again, let's take
a look at our topology

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to remember where
we are and what

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we're going to be configuring.

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And then we'll jump
into the command line

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and get these things configured.

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So the first thing we're
going to do in this video

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is we're going to be
configuring Area 20 and Area 30,

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which is, of course, going
to involve configuring

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routers 8 and 9.

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Once that's done, we're
going to take a closer

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look at our backbone
because as of right now,

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our backbone effectively
looks like this.

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We have level-2 going between
router-1 and router-2,

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to 3, out to 4.

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Of course, from 1 down
to 7, from 3 over to 7,

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and from 1 to 6, and
6 to 7, since this

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is a multi-axis segment.

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Now, of course, once we
bring in routers 8 and 9,

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this backbone will be extending
out to those areas as well.

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However, we do have a
single point of failure.

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And what we're going to
be doing is taking a look

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at what happens if this
link were to go down.

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How does that affect things
when it breaks level-2?

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So these are the things
we're going to be exploring,

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but we'll begin by
building those other areas.

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So let's start on the
command line of router-8

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and bring it in to Area 20.

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Now, at this point, we've
configured quite a few routers

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for IS-IS.

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So rather than going
through these step by step,

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we'll just go ahead and
paste the configuration in.

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The only thing of real
note here is, of course,

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the area number being 20.

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So as long as we're
familiar with that,

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this is the stuff
we've configured on all

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of the other routers, so far.

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So this puts router-8
into Area 20.

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It should also, of course,
bring up a neighborship.

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We do a show ISS neighbor.

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And of course, the console
messages were already

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telling us this already,
but we see here of course,

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that our neighborship with
router-7 is, in fact, up.

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If we do a show IS-IS database,
notice that we have both

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a level-1 and the level-2
database because this is

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a level-1/level-2 router.

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Technically, it really only
has to be level-2 because

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of our environment.

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But if we were to bring other
devices into Area 20 here,

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maybe we would want to talk
just level-1 with them.

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So therefore, it's probably
a good idea to leave router-8

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as a level-1/level-2.

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If we do a show
IP route IS-IS, we

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should also see
all of our routes

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here in router-8's routing
table, which, as we can see,

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we do.

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Let's do the same
thing now on router-9.

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Once again, we'll just
paste in the configuration,

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noticing that the only
thing, again, really changing

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here is the area is now 30.

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As we can see here on
the console message,

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our neighborship to router-2
has already come up.

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So let's go ahead and do
a show IP route IS-IS.

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And as we can see
here, we're now

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learning all of the routes
here on router-9 as well.

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So this indicates
that all of our areas

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are up and running in IS-IS.

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So now that all of our
areas are up, let's go ahead

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and test that redundancy
we talked about and really

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see what happens
when level-2 breaks.

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So we're going to
go into router-2

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and shut down its
gigabit interface

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over towards router-1.

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So again, this is
interface gigabit-0000.

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And we'll simply do a shut
and commit the changes.

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Now that we've
created a failure,

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let's see how this has affected
the IS-IS routing table.

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Let's first go back to router-9.

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And on router-9, we see that
we just had all these routes.

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Let's see what we have now.

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Notice now that
we literally only

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have the routes coming pretty
much directly from Area 10.

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We don't have any of the routes
from Area 100, or Area 20

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way out there on router-8.

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So this has severely impacted
the routing table on router-9

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even though we still
have a neighborship up

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between router-2 and router-4.

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And router-4 would still
have all the routes.

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Let's verify that.

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If we look at the routing
table on router-4,

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we see that it, in fact, does
still have all the routes,

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except the one from router-9.

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Notice, we don't have
router-9's loopback.

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So we have a breakage
here in level-2

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between router-9 and router-4
because there's no redundancy

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in our level-2 environment.

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Now, to fix this,
all we really have

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to do is take that
level-1 link that's

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on the LAN between
routers 2, 4, and 5

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and convert at least the
connection between routers 2

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and 4 to include level-2.

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If they include a level-1
and a level-2 adjacency,

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then it will fix this
problem because it

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would be fixing the backbone.

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So let's go ahead and do that.

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We'll just reconfigure that
link to be level-1 and level-2

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on routers 2 and 4.

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So simply go into configuration
mode, router IS-IS 1

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for interface gig-0001.

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And we'll simply change the
circuit-type to level-1-2.

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We'll commit that change and
do the same thing on router-2.

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So again, configure
it for level-1-2.

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Commit the changes.

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Here, we'll just go back
to global configuration

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because ultimately, we'll bring
that gigabit-0000 interface

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back up.

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But let's see if this has
fixed the problem first.

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Again, since router-9 was the
one having the major problem,

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let's go back and
check on router-9.

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So once again, we'll just
do our show IP route IS-IS.

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And notice, we now have all
of the routes back again

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because now, they're
being learned

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through router-3 over to
router for up to router-2

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and then to router-9,
even though that link

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between router-2 and
router-1 is still down.

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We can verify that
if we were to say

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trace to router-7's loopback,
sourcing it from our loopback.

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We can see here
that the path itself

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is going from router-2 to
router-4 to router-3 router-7.

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It's not going through router-1.

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That link is currently down.

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So now that we've seen how
to fix it, let's go ahead

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and bring router-2's
interface back-up.

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We don't want to
leave this broken.

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We'll give that just a second
to come back up and stabilize.

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We'll go back to router-9.

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And let's check our trace again.

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Notice this time, it's going
router-2, router-1, router-7.

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That is a shorter path.

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We couldn't go that
way, of course,

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while the link was
down, but at least

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we still had a
redundant path even

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though it was a hop longer.

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So in this video, we
brought some routers

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into some other areas.

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We brought Area 20
and Area 30 online.

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Although, we've seen that
already in previous videos.

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The main thing we
wanted to see here

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was how to add
some redundancy to.

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Well, in this
case, of course, we

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did Area 10, which could
be argued that it's

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acting as a transit area.

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Although, there's not really
backbone areas and transit

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areas in IS-IS.

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What we really did
is add redundancy

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to the level-2 path, which, of
course, is what's ultimately

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acting as our backbone.

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I hope this has been
informative for you,

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and I'd like to thank
you for viewing.

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