[AUDIO LOGO]
Now that we have our one-way redistribution done into IS-IS,
let's move on to OSPF.
So in this video, we're going to redistribute
both EIGRP and IS-IS, as well as connected into OSPF.
So let's bring up our topology design
where we're going to do this.
And then we'll jump into the command line
and do some redistribution into OSPF.
And of course, look at some of the caveats as we go.
So what we're going to configure now
is we will configure router 1 to redistribute EIGRP into OSPF.
We'll do the same thing on router 2.
Then we'll configure router 1 to redistribute IS-IS into OSPF
and do the same thing on router 3.
And of course, we'll be looking at these routes
on various different routers through our topology.
So let's jump into the command line
and get started with our redistribution.
So for this demonstration, let's start off on router 5
with simply a show ip route ospf.
And all we want to really look at
is we just currently have internal OSPF routes.
That's all we have on router 5 right now.
So let's jump up to router 1 and configure our redistribution
from EIGRP into OSPF.
So we'll simply go in and configuration mode,
into router OSPF 1, into our address family.
And let's do a redistribute eigrp 100.
And if we hit question mark after this,
we'll see we have some different choices here.
We can match on certain criteria or set the LSA type
for redistributed routes, do things like redistribute only
into NSSA.
Of course, we can run our redistribution
through a route policy that we could use for filtering
or route manipulation.
But what we want to do right now is just tag these routes.
And what we're going to do is we're going to tag them as 90.
Now, realistically, you can use any tag you want.
In a relatively simple environment,
I usually use the tag that's based
on that routing protocol's admin distance
just because it's easy to remember.
And then later, we can easily see that this came from EIGRP.
Of course, if you want to use any other tags,
that's perfectly fine.
And in a more complex environment
where say, for example, we had more than one EIGRP AS,
well, we would have to use different tags,
or else, we wouldn't be able to tell
the difference between them.
But in a simple environment, I just find this as an easy way
to do tags.
So we'll go ahead and configure that.
Commit those changes.
And we'll exit configuration.
As far as doing some verification,
we can start with a show ip ospf database.
We'll filter by external routes.
And we'll say self to indicate self-originating.
These are the external routes that we are
putting into the OSPF database.
We can see here that we're bringing in say,
for example, router 9's loopback.
Here, we have the link between router 1 and router 9.
Here, we have the link between router 2 and router 9.
And then we have some additional loopback interfaces on router 9
that we're also bringing into OSPF.
So we can, of course, see these if we go back over to router 5.
Let's do our show ip route ospf again.
But this time, let's filter it and say
to include anything that's OSPF and external.
What we see here is all of those prefixes
that we just saw on the database--
now being brought in as external type 2's into OSPF.
This is, of course, exactly what we're looking for.
If we were to pick on one of these prefixes,
so let's just say, for example, the 100.9.9.0,
we can also see that route tag being applied here--
the route tag of 90.
We can, of course, see this in the database as well.
And we see here where the external route tag is set
to 90 in the database as well.
Now, let's go ahead and configure the redistribution
on router 2 as well.
Now, we're going to partially copy and paste this,
but we're going to stop here at the tag.
And the reason is we're going to go a little further this time.
And we're going to set the metric type to be type 1.
We saw just a moment ago that the default is to bring routes
into OSPF as external type 2.
Well, let's go ahead and change that,
bring them in as external type 1 on router 2
just to do it a little different.
We'll commit our changes and exit configuration.
Let's go ahead and look at those self-generated external LSAs
again.
We see that once again, we are generating all of those LSAs.
They are, however, a type 1 this time,
and they are still being tagged.
We see it as all the same entries
here as we scroll through the database.
So now, what should have happened if we jump back over
router 5, is router 5 should now be preferring all the E1's.
Because remember in OSPF, external type 1's get chosen
over external type 2's.
So we can see that it's now choosing all the external type
1's, which are coming from router 2.
So now that we have EIGRP routes in OSPF,
let's bring in the IS-IS routes as well.
So let's go over to router 1.
Of course, we go back into OSPF address-family.
And we'll say to redistribute IS-IS process 1.
And we'll go ahead and tag those as 115,
which, of course, is IS-IS's administrative distance.
We'll commit those changes.
Exit configuration.
And we're going to configure the exact same thing on router 3.
So we'll just copy and paste that configuration.
So here on router 3, we'll just paste that in.
And now, let's go check router 5 again.
So once again, we'll look for all
of the OSPF external routes.
And notice that we have considerably more routes now.
We have all the routes coming from the IS-IS domain,
including, for example, this 88.88.88.0,
which we know is coming from router 8.
So now that we have mutual redistribution on two routers,
we know that both routing domains should
have routes for each other.
Now, we can hop over to router 7 or router 8,
look at their routing tables, and make sure
that they have the OSPF routes.
But we did do that in the previous video
when we redistributed into IS-IS.
So that should still be OK.
Now would be a good time to test connectivity.
Let's go ahead and trace to that 88.88.88.88,
and we will source that from our loopback 0 interface.
As you can see, this is a routing loop.
Our traffic is going to router 2,
then to router 1, then to router 7,
then to router 3, then back to router 1, back to router 7,
back to router, and so on.
So this is entering a routing loop.
And this is exactly what we said can happen if you don't control
routing loops when you do mutual redistribution on two routers.
But let's take a look at our routing tables
and figure out why this is happening.
The biggest giveaway is just going
to be to go look at router 7.
Let's just start with that show ip route.
Just verify that we do still have all of those routes
that we're supposed to have.
We can see that we do.
However, we do have a rather large problem.
If we look at that 88 route.
Now, what's interesting is this is showing it
that it's load-sharing.
But the fact of the matter is, it really is not load-sharing.
It's sending the traffic back to router 3.
We saw that in our trace.
So just so we fully understand the problem,
let me bring up the diagram again.
So let's remember what's happening here.
Router 8 is sending this update to router 7.
Router 7 is sending it to router 1 and router 3 through IS-IS.
Now remember, IS-IS has an admin distance of 115.
So then, one of the routers.
And in this case, just based on the evidence,
we can say that it's router 1.
1 is taking that route and redistributing it into OSPF.
Then what happens is OSPF sends this down to router 3.
Router 3 now has an admin distance of 110 versus 115.
And what it's essentially doing is replacing the IS-IS route
in its routing table with the OSPF route.
Once that's done, this part is not happening anymore.
So now, since router is configured, of course,
to redistribute OSPF back into IS-IS, it's doing just that
and sending this update right back to router 7.
Router 7 now has two IS-IS routes,
which, again, theoretically, it should be load-sharing.
But we could tell by the trace, it's not.
It's sending the traffic right back to router 3.
And this is why we have the loop.
We'll be solving this in an upcoming video.
We're not going to tackle this right now.
But that's the problem.
And that's why we have this loop.
In this video, we looked at how to redistribute routes
into OSPF.
A couple of things to note about that--
first, all the routes come in by default as an external type 2,
which, of course, we can change on the redistribution,
like we did on router 2.
Also, we didn't exactly point this out
as we went because we had discussed it
earlier in our previous videos.
However, if you didn't notice it,
you can go back and look that all
of those routes we redistributed came in with that default seed
metric of 20 because we didn't change that.
Also, we got our first look here at a routing loop
being caused by redistribution.
And of course, we'll be solving that later.
Before we do, though, we're going
to configure redistribution into RIP.
And that's exactly what we're going to do next.
Until then.
I hope this has been informative for you,
and I'd like to thank you for viewing.