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[AUDIO LOGO]

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So in the last video, we saw
the showdown between internal

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versus internal routes.

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But what about external
versus external?

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Now, externals don't have that
same marking, so to speak,

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of being either from your own
area or from a different area.

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However, there are two different
types of external routes.

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There's external type
1 and external type 2.

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Now, generically speaking, what
that means is with a type 2,

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we're going to not
track internal cost.

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Now, we'll see in our
upcoming videos that in a way,

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we still sort of do
because there's something

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called the forwarding metric.

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And we have to look at that.

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However, it's not stored right
in the metric of the route.

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With a type 1 external,
the metric for the route

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is actually calculated by
looking not only at the type 5

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LSA but also by looking at
the distance or the cost

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to the exit.

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That is then put
together into the metric

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in the routing table.

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And we'll see this as we go.

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But as always, let's start
by jumping into our topology,

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taking a look at what
we're going to build,

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and then jumping
into the command line

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and seeing all of this work.

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As we jump into
this demonstration,

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it is important to note that
the previous internal instances

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of this route that were
on router 8 and router 5

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have at this point been removed.

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We now just have the one
instance on router 10.

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Again, this is of the
100.100.100.0/24 network.

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This is being redistributed
on router 10 into OSPF.

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And it's coming
in as the default

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type of an external type 2.

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We're going to start by
examining that external route.

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As per usual, we'll take
a look at it on router 7.

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And then what we're
going to do is

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we're going to create this
loopback on router 5 again.

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But this time, we're not going
to bring it in as internal.

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We're going to
redistribute this into OSPF

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and bring it in as
an external type 1.

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So we're going to create
this type 1 external.

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And we're going to
give it a high cost.

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Again, we're trying
to prove the rule

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that the E1 will
be believed over

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the E2 regardless of the cost.

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That's the point of this.

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So by bringing it
in with a high cost,

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we'll be able to prove that.

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We'll also examine a little
bit about that E1, how

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the metric looks, and so on.

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So we will not only be observing
that the type 1 beats the type

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2, but we'll also
see what the E1 looks

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like as far as
the metric in both

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the LSA and the routing table.

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So let's jump in and
get started by looking

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at that route on router 7.

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So if we look at the routing
table here on router 7,

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right now, it's an
external type 2.

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And it has a metric of 20
and a forward metric of 2.

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Keep these numbers in mind as we
go through this demonstration.

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Now, one other thing to note, if
we look at the database itself,

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notice the metric here
is also listed as 20.

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So one of the fundamental
characteristics

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of the external type 2
is that the metric shown

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in the routing table,
in this case 20,

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is the same as the metric shown
in the database on the type

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5 LSA--

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again, in this case a 20.

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Now let's bring in a type 1.

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So let's go over and
do this on router 5.

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So on router 5, we'll make
our new interface loopback 100

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interface.

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But this time, instead of
actually running OSPF on it,

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we're instead going to
go into router OSPF 1.

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We'll do a redistribute
of connected routes.

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We'll set the metric type.

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And of course, we have
our two choices here.

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The default is metric type
2 if you don't specify.

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We're going to specify
a metric type of 1.

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And as we mentioned
previously, we're

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going to set this to
a rather high metric.

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Let's just set it to 5000.

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We can verify this if we do a
show ip ospf database external.

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And we'll filter it
by self originated.

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And we see exactly
what's going on here.

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We see that it is
a metric type 1.

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And we see that it has
that metric of 5000.

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So now let's, of course,
go back to router 7

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and observe what's happening.

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First thing we're
going to do on router 7

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is look at the database again.

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So let's again look at
that same exact command.

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But of course, this time
we have this new LSA,

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the one from advertising
router 10.5.5.5.

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Notice the metric.

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The metric is still 5000.

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Here's the thing with
the type 1 external.

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It does track internal
cost when it puts the route

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into the routing table.

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But here in the database,
notice that it still

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has this metric of 5000
through the entire network.

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The type 5 LSA itself
is never changed.

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But what the type 1 external
tells the receiving router

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to do is to take this metric
of 5000 and add it to our cost

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to the exit.

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Let's take a look at
how that's put together.

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So if we were to say
show ip ospf border,

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notice that our cost to get
to our advertising router

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of 10.5.5.5, it actually
has a cost of 3,

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which means that if I say show
ip route for the 100.100.100.0,

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that means that the metric
shown in the routing table is

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actually 5003.

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That's the 5000 coming from
the type 5 LSA added to the 3

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that it costs me to get
to the advertising router.

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Now, since I have two equal
costs to get to the advertising

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router, you can see here we
are, in fact, doing load sharing

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as well to this new route.

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So two big things we
saw in this video--

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number one is that
that external type

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1 beats the external type
2, regardless of the metric.

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Once again, we started off with
a route with a metric of 20.

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Now we have a route
with a metric of 5003

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just because it's a type 1.

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The other thing is when you
have that external type 1,

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the actual type 5
LSA itself is not

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modified, except for
the fact that it says

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that it's a type 1, of course.

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But what that type 1 indicates
to the receiving device

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is that it should take the
metric from the type 5 LSA

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and add that to the cost to
get to the advertising router

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when it puts that route into
the routing table itself.

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That way, the routing table
reflects the total costs

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to get to that 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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