So now it's time to talk about bringing the ultimate summary
route into OSPF, the default route.
Because that is a summary of all other routes.
That's what a default is.
Now back in our skill on OSPF special area types,
we've already discussed some ways
that a default comes into OSPF.
A stub area, for example, always generates a default,
as does a total stub and a total NSSA.
Now, an NSSA can also originate a default route,
but we have to do that manually.
Well, the way we do it in a normal area
is also very similar to the way we do it in that normal NSSA.
And that's what we're going to be focusing on in this video.
how do we bring a default route into OSPF other
than our special area types?
So let's jump to our topology real quick,
just to take a look at where we're going to bring it in.
And then we'll jump on to the command line,
and we'll see this in action.
So very simply, in this case, we're just
going to bring in a default route on router 10,
have it inject it into the rest of the OSPF environment.
Now as we jump into this, keep in mind
that currently, router 10 does not have its own default
route going anywhere.
So that's just something we need to keep in mind as we
jump into the command line.
So since we know there's no defaults anywhere
at this point, there's nothing really
to look at before we begin.
So let's just jump right into the command line on router 10.
So what we'll do here on router 10 is,
under the router OSPF process, we
will use the default information originate command.
We'll hit Enter.
And this is supposed to inject a default into OSPF.
Let's just jump right over to router 6 to see if it has.
If we do a show IP route OSPF, we
see that there is no default route.
The reason we're not getting this default route here
on router 6 is because in order for the default information
originate command to actually send in a default,
the router doing the default information originate
has to have its own default route.
And in this case, router 10 does not.
Therefore, default information originate
is not doing anything.
In order to get it to work, we really have two choices.
Choice number one is, we can simply give router 10 a default
route, in which case that'll meet the criteria,
and router 10 will start sending a default route into OSPF.
And we'll do that option first.
But in some situations, you may not
want router 10 to have a default route.
Or maybe for some reason, it can't, in which case
there's an additional option on the default information
originate command that we can use to tell it to originate
that default, even if that router itself does not
have its own default route.
So we'll take a look at that option second.
But let's start by putting a default route onto router 10.
So back up here on router 10, we will simply
make up a default route.
We'll just say that it's going to route the default
to say loopback 0, which of course, is not really
a valid default gateway.
And it's sort of telling us that here as well in the message.
But that's OK.
If we do a show IP route, it did, in fact, still take it.
So even though it's, of course, really not valid,
that's not going to matter a whole lot to OSPF.
Let's go take a look at router 6 again.
On router 6, if we look at our route again,
we see that we are now, in fact, getting that external type 2
default from router 10.
So another important thing to note here
is that default information originate brings that default
route in as an external type 2.
Now this default should be propagating
through our entire OSPF domain.
So let's just pick another router, such as router 4,
to verify.
So on router 4, we'll do a show IP route.
And we see that this router also has
that default equals now that's being originated into OSPF.
So now let's look at the second option.
Let's go back to router 10.
We will take out that default route we just put in.
We'll go back into the router OSPF process.
And on the default information originate command,
we will say always.
Notice, by the way, there are some other options here,
which we're not going to explore.
But we could, if we wanted to, manually set a metric
or change the metric type.
So if we wanted this to be, say, for example, an external type
1, we could change that.
Or we can also run this through a route map
to change various attributes of the route.
In this case, we're just going to go ahead and say always.
So now, if we do a show IP route on router 10, notice,
it no longer has a default route.
However, if we go back to, say router 6 again,
we look at our routing table again,
we still have a default. And again,
It should be propagated through the entire domain.
We could verify again on router 4.
We'll do the show IP route here on router 4 again.
And we can see that we do, in fact, still
have this default route.
In this video, we looked at originating a default route
into OSPF, specifically using the default
information originate command.
Our key takeaways here would be that if you just
say default information originate by itself,
there is a requirement that router already
have its own default route in its routing table.
If you cannot or do not want to supply that router with
a default route, then you can add the keyword always
to the default information originate,
and it will always generate a default route,
even if that router itself does not have a separate default.
I hope this has been informative for you,
and I'd like to thank you for viewing.