[AUDIO LOGO]
So now that we've configured our other areas, in this video,
we're going to finish up by configuring Areas 20 and 30.
And we're also going to look at providing some redundancy
to our backbone.
As it is right now, we have some points in our network
where a single failure could cause us some problems.
So once again, let's take a look at our topology
to remember where we are and what
we're going to be configuring.
And then we'll jump into the command line
and get these things configured.
So the first thing we're going to do in this video
is we're going to be configuring Area 20 and Area 30,
which is, of course, going to involve configuring
routers 8 and 9.
Once that's done, we're going to take a closer
look at our backbone because as of right now,
our backbone effectively looks like this.
We have level-2 going between router-1 and router-2,
to 3, out to 4.
Of course, from 1 down to 7, from 3 over to 7,
and from 1 to 6, and 6 to 7, since this
is a multi-axis segment.
Now, of course, once we bring in routers 8 and 9,
this backbone will be extending out to those areas as well.
However, we do have a single point of failure.
And what we're going to be doing is taking a look
at what happens if this link were to go down.
How does that affect things when it breaks level-2?
So these are the things we're going to be exploring,
but we'll begin by building those other areas.
So let's start on the command line of router-8
and bring it in to Area 20.
Now, at this point, we've configured quite a few routers
for IS-IS.
So rather than going through these step by step,
we'll just go ahead and paste the configuration in.
The only thing of real note here is, of course,
the area number being 20.
So as long as we're familiar with that,
this is the stuff we've configured on all
of the other routers, so far.
So this puts router-8 into Area 20.
It should also, of course, bring up a neighborship.
We do a show ISS neighbor.
And of course, the console messages were already
telling us this already, but we see here of course,
that our neighborship with router-7 is, in fact, up.
If we do a show IS-IS database, notice that we have both
a level-1 and the level-2 database because this is
a level-1/level-2 router.
Technically, it really only has to be level-2 because
of our environment.
But if we were to bring other devices into Area 20 here,
maybe we would want to talk just level-1 with them.
So therefore, it's probably a good idea to leave router-8
as a level-1/level-2.
If we do a show IP route IS-IS, we
should also see all of our routes
here in router-8's routing table, which, as we can see,
we do.
Let's do the same thing now on router-9.
Once again, we'll just paste in the configuration,
noticing that the only thing, again, really changing
here is the area is now 30.
As we can see here on the console message,
our neighborship to router-2 has already come up.
So let's go ahead and do a show IP route IS-IS.
And as we can see here, we're now
learning all of the routes here on router-9 as well.
So this indicates that all of our areas
are up and running in IS-IS.
So now that all of our areas are up, let's go ahead
and test that redundancy we talked about and really
see what happens when level-2 breaks.
So we're going to go into router-2
and shut down its gigabit interface
over towards router-1.
So again, this is interface gigabit-0000.
And we'll simply do a shut and commit the changes.
Now that we've created a failure,
let's see how this has affected the IS-IS routing table.
Let's first go back to router-9.
And on router-9, we see that we just had all these routes.
Let's see what we have now.
Notice now that we literally only
have the routes coming pretty much directly from Area 10.
We don't have any of the routes from Area 100, or Area 20
way out there on router-8.
So this has severely impacted the routing table on router-9
even though we still have a neighborship up
between router-2 and router-4.
And router-4 would still have all the routes.
Let's verify that.
If we look at the routing table on router-4,
we see that it, in fact, does still have all the routes,
except the one from router-9.
Notice, we don't have router-9's loopback.
So we have a breakage here in level-2
between router-9 and router-4 because there's no redundancy
in our level-2 environment.
Now, to fix this, all we really have
to do is take that level-1 link that's
on the LAN between routers 2, 4, and 5
and convert at least the connection between routers 2
and 4 to include level-2.
If they include a level-1 and a level-2 adjacency,
then it will fix this problem because it
would be fixing the backbone.
So let's go ahead and do that.
We'll just reconfigure that link to be level-1 and level-2
on routers 2 and 4.
So simply go into configuration mode, router IS-IS 1
for interface gig-0001.
And we'll simply change the circuit-type to level-1-2.
We'll commit that change and do the same thing on router-2.
So again, configure it for level-1-2.
Commit the changes.
Here, we'll just go back to global configuration
because ultimately, we'll bring that gigabit-0000 interface
back up.
But let's see if this has fixed the problem first.
Again, since router-9 was the one having the major problem,
let's go back and check on router-9.
So once again, we'll just do our show IP route IS-IS.
And notice, we now have all of the routes back again
because now, they're being learned
through router-3 over to router for up to router-2
and then to router-9, even though that link
between router-2 and router-1 is still down.
We can verify that if we were to say
trace to router-7's loopback, sourcing it from our loopback.
We can see here that the path itself
is going from router-2 to router-4 to router-3 router-7.
It's not going through router-1.
That link is currently down.
So now that we've seen how to fix it, let's go ahead
and bring router-2's interface back-up.
We don't want to leave this broken.
We'll give that just a second to come back up and stabilize.
We'll go back to router-9.
And let's check our trace again.
Notice this time, it's going router-2, router-1, router-7.
That is a shorter path.
We couldn't go that way, of course,
while the link was down, but at least
we still had a redundant path even
though it was a hop longer.
So in this video, we brought some routers
into some other areas.
We brought Area 20 and Area 30 online.
Although, we've seen that already in previous videos.
The main thing we wanted to see here
was how to add some redundancy to.
Well, in this case, of course, we
did Area 10, which could be argued that it's
acting as a transit area.
Although, there's not really backbone areas and transit
areas in IS-IS.
What we really did is add redundancy
to the level-2 path, which, of course, is what's ultimately
acting as our backbone.
I hope this has been informative for you,
and I'd like to thank you for viewing.