[MUSIC PLAYING]
So now that we've seen internal versus external, now
it's time for the showdown between internal and internal.
And of course, what we mean by that is intra area,
meaning routes learned within my own area,
versus inter area routes learned from a different area.
So effectively, we're talking about routes
that would be learned from a type 1
or a type 2 LSA for the area.
And for a type 3 LSA, for the inter area.
So once again, let's jump to our topology
just to get a quick look at what we're
going to be setting up and demonstrating.
And then we'll jump onto the command line
and see this in action.
So in this demonstration, let's pick up right where we left off
in our previous video.
We already have a loopback on router 8.
Again, this is the 100.100.100.0/24 network.
And router 7 is currently preferring that.
So we're going to start by examining this existing intra
area route.
We'll take a look at it on router 7.
And then we'll create an inter area route with a low cost.
Again, the idea here is we'll try
to get it to prefer this inter area version.
We'll create this on router 5.
And again, we'll be bringing that
in with a very low cost trying to get router 7 to prefer that.
And of course, knowing our rule here,
when we look at these results, what we should see
is that router 7 is still going to be following the route
to router 8, again, regardless of the cost
because the intra area should beat the inter area
route coming from router 5.
So again, let's start out with our observations
here on router 7.
So again, we'll start off looking at that prefix.
And we see that it is in fact being learned as an intra area
route with a metric of 1001.
And that this is coming from router 8.
Router 8 also happens to be our next hop.
So now let's create this inter area route
by jumping over to router 5.
So on router 5, we'll create an interface loopback 100.
We'll set the address to 100.100.100.5.
Once again, make it a /24.
We of course, have to make the network type point to point.
And we put this into area 100.
Now we don't have to set the cost on this one
because if we do a show IP OSPF interface for loopback
100, what we'll see is the default cost on this
is already a one.
So that's pretty much as low as it's going to get.
So we're not going to be able to go any lower than that.
But that should certainly beat the 1,000 coming from router 8.
So let's jump back over to router 7 and view the results.
Now again, it shouldn't be any big surprise
that if we look at the route again,
it's exactly the same as it was before.
Nothing's changed by us bringing in this other route.
This is because the intra area route is being preferred.
But we should at least verify that we're
getting the other one.
So let's do a show IP OSPF database.
And we'll say summary for the 100.100.100.0.
Now we see we're actually getting two copies of this.
One from 10.1.1.1.
The other one, of course, from 10.3.3.3, the two ABRs.
But the important thing is notice on both of these,
the metric is three, which is certainly a heck of a lot
lower than 1001.
So once again, this is not coming down to lowest cost.
This is coming down to preferring
a route within your own area before you
prefer to go to another area.
So in this video, we took a look at our second rule
in the OSPF path selection process,
which is simply to prefer an intra area route over an inter
area route.
And once again, we proved that this is happening long
before the lowest cost because ours
was a significantly lower cost.
And it still didn't get chosen as best.
That area route still won over the inter area route.
I hope this has been informative for you.
And I'd like to thank you for viewing.