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[MUSIC PLAYING]

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So now that we've seen
internal versus external, now

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it's time for the showdown
between internal and internal.

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And of course, what we
mean by that is intra area,

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meaning routes learned
within my own area,

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versus inter area routes
learned from a different area.

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So effectively, we're
talking about routes

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that would be
learned from a type 1

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or a type 2 LSA for the area.

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And for a type 3 LSA,
for the inter area.

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So once again, let's
jump to our topology

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just to get a quick
look at what we're

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going to be setting
up and demonstrating.

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And then we'll jump
onto the command line

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and see this in action.

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So in this demonstration, let's
pick up right where we left off

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in our previous video.

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We already have a
loopback on router 8.

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Again, this is the
100.100.100.0/24 network.

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And router 7 is currently
preferring that.

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So we're going to start by
examining this existing intra

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area route.

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We'll take a look
at it on router 7.

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And then we'll create an inter
area route with a low cost.

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Again, the idea
here is we'll try

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to get it to prefer
this inter area version.

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We'll create this on router 5.

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And again, we'll
be bringing that

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in with a very low cost trying
to get router 7 to prefer that.

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And of course,
knowing our rule here,

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when we look at these
results, what we should see

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is that router 7 is still
going to be following the route

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to router 8, again,
regardless of the cost

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because the intra area
should beat the inter area

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route coming from router 5.

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So again, let's start
out with our observations

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here on router 7.

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So again, we'll start off
looking at that prefix.

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And we see that it is in fact
being learned as an intra area

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route with a metric of 1001.

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And that this is
coming from router 8.

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Router 8 also happens
to be our next hop.

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So now let's create
this inter area route

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by jumping over to router 5.

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So on router 5, we'll create
an interface loopback 100.

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We'll set the address
to 100.100.100.5.

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Once again, make it a /24.

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We of course, have to make the
network type point to point.

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And we put this into area 100.

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Now we don't have to
set the cost on this one

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because if we do a show IP
OSPF interface for loopback

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100, what we'll see is
the default cost on this

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is already a one.

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So that's pretty much as
low as it's going to get.

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So we're not going to be able
to go any lower than that.

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But that should certainly beat
the 1,000 coming from router 8.

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So let's jump back over to
router 7 and view the results.

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Now again, it shouldn't
be any big surprise

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that if we look at
the route again,

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it's exactly the same
as it was before.

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Nothing's changed by us
bringing in this other route.

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This is because the intra
area route is being preferred.

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But we should at least
verify that we're

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getting the other one.

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So let's do a show
IP OSPF database.

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And we'll say summary
for the 100.100.100.0.

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Now we see we're actually
getting two copies of this.

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One from 10.1.1.1.

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The other one, of course,
from 10.3.3.3, the two ABRs.

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But the important thing is
notice on both of these,

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the metric is three, which
is certainly a heck of a lot

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lower than 1001.

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So once again, this is not
coming down to lowest cost.

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This is coming
down to preferring

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a route within your
own area before you

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prefer to go to another area.

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So in this video, we took
a look at our second rule

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in the OSPF path
selection process,

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which is simply to prefer an
intra area route over an inter

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area route.

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And once again, we proved
that this is happening long

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before the lowest
cost because ours

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was a significantly lower cost.

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And it still didn't
get chosen as best.

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That area route still won
over the inter area route.

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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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