If we had a pet, we'll use a dog because it's
more applicable to a dog than the cat.
If we had a dog, when would be the best time
to train that dog on how to behave?
And the answer is as soon as possible--
when it's young, when it is fresh, when it's new.
Well, we have the same opportunity with routing
and with route control when we do redistribution from one
routing protocol to another.
That's the perfect time where we can implement some controls
and tweaking to make those routes behave the way we want. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and tweaking to make those routes behave the way we want.
So let me share with you the topology.
And then some ideas regarding redistribution and some
controls we can put in place at the point of redistribution.
So with this topology, let's imagine
that we have this part of our network using all one common
routing protocol.
We'll call it, let's call it OSPF.
That way we can put some teeth on it, as opposed
to routing protocol A.
And then down below, down here, let's
go ahead and have all these guys run, let's pick, EIGRP. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
go ahead and have all these guys run, let's pick, EIGRP.
All right.
So first of all, this is not a great design.
However, if we had OSPF domain and the EIGRP domain
that we want to share the routes,
one of the key tricks I use is make
sure we're focusing on one route at a time, or one network.
So let's say, for example, this 12 network
up here between R1 and R2, if we want reachability on here
and this is EIGRP domain, they're
going to need either a default route
or they're going to need to learn that route,
and vice versa.
If we want the 78 network to be learned by router 1 or router
2, but you're not running EIGRP, we've WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
2, but you're not running EIGRP, we've
got to somehow either give them default routes
or give them that information by redistributing EIGRP into OSPF.
So as far as manipulation and control, check this out.
When we do the redistribution of OSPF, the way we do it is we
go into router configuration mode for EIGRP.
And then we'd say redistribute OSPF into EIGRP.
Now, the problem, the problem is that the metrics
are all wacky doodle different.
OSPF uses costs and EIGRP uses the composite metric WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
OSPF uses costs and EIGRP uses the composite metric
with bandwidth and delay being the two major factors.
So how do we deal with that?
Well, when we bring in a route when we do the redistribution
on this guy, R3, we're going to specify what
we want that seed metric to be.
We can set a default or we can do it
at the point of redistribution with a command.
We can say, OK, any new routes that are coming in
as far as manipulation and control,
we want them to have a bandwidth of XYZ.
And we want the delay to be XYZ.
So we can make the route look as good or as bad
as we want based on that redistribution into EIGRP. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
as we want based on that redistribution into EIGRP.
Then once they're there, they're going to show up as external.
So that's what an external EIGRP route is.
It is redistributed in from another source of static routes
or another routing protocol.
And so external routes in EIGRP have an administrative distance
of 170.
So they're not going to be preferred compared
to the non-external routes with EIGRP which have an AD of 90.
So just right there, if these routers have to choose a route, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So just right there, if these routers have to choose a route,
they're going to go ahead and choose
the route with an AD of 90 if there's duplicates in place.
So by default some of the defaults are going to help us.
Now, the other element is, if we wanted to redistribute EIGRP
into OSPF, we could do it also right
here-- which is not a bad idea-- on the same router.
That's going to help prevent loops.
And then as we bring EIGRP routes in,
we have some choices.
They are going to be external routes in OSPF
once we redistribute them in, including the 78 network.
But we can specify, do we want it
to be a type 1, external type 1 where the metric can WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
to be a type 1, external type 1 where the metric can
grow and grow and grow as that route gets propagated in OSPF,
or do we want it to be an external type 2?
Type 2, I'm fixed.
My metric is fixed.
That's all I do.
So inside of OSPF, we can control that.
And also what we can do is when we bring routes back and forth,
we can also tag them.
And you might say, Keith, what's the benefit of a tag?
Tags are helpful in the condition
where we, if we're doing redistribution over here--
this is just an example-- on R4 of EIGRP into OSPF and OSPF WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
this is just an example-- on R4 of EIGRP into OSPF and OSPF
into EIGRP for fault tolerance-- we
have two routers that are behaving
that way-- we could, on the redistribution,
we could tell the routers, hey, listen.
Any external EIGRP routes, don't bother bringing in.
I mean, they're already external.
So that's a very elegant way of controlling the device
and saying, you know what?
These are external routes, like, the 12 network
as an external in EIGRP.
Don't bother bringing it in.
That's great.
We might have other scenarios, though, where
if we tag them, if we, on R3, if we tagged all the routes WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
if we tag them, if we, on R3, if we tagged all the routes
as they came in and we added a tag of, let's say, 999.
Just a number.
So R3 tags 999 as he brings him in,
R4 tags 999 as he brings him in.
Then we could tell the routers, hey, listen.
If it has a tag of 999, that route,
don't bother bringing it in.
We can control that with route maps.
So we can tag using route maps.
Some routing protocols allow us to tag directly.
We'll do that in the next lab.
And we also, when we redistribute,
we can refer to a route map that's looking for a tag of 999 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
we can refer to a route map that's looking for a tag of 999
and saying, not going to bring it in.
Now, the great news is this.
The great news is this.
We have a lot of tools and options
when we're doing redistribution.
And here's one of the key elements
that I learned a long, long time ago in a network far away,
is that we want to avoid, which is
another way of saying don't, don't
redistribute a route that was sourced
from one routing domain, like, OSPF at the 12 network.
Don't redistribute that same route back into OSPF.
So in some, like, a CCIE environment where they have, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So in some, like, a CCIE environment where they have,
this domain and that domain, the key
is just make sure that a route that was sourced in OSPF,
or we'll call this routing protocol 1, routing protocol 1.
And we'll call EIGRP routing protocol number 2.
Make sure that any routes that were sourced originally
from routing protocol 1 and then they're redistributed
into a different routing protocol 2,
make sure we're never going to redistribute those back
in to the original routing domain
because that is what's going to lead to loops. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
because that is what's going to lead to loops.
So EIGRP and OSPF have so many defense mechanisms in place.
For example, OSPF, if it has the same route
that it's learned via an intra-area route
versus an inter-area route, it's going to choose the intra.
So that's going to be chosen regardless of metric.
And if it has an external type 1 and an external type 2,
it's going to choose the external type
1 every day over the external type
2 because that's how it's built. So in these two scenarios,
it's actually pretty tough to have a routing loop because WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
it's actually pretty tough to have a routing loop because
of the defaults with the AD's and the preference
for these routing protocols that they use by default.
So the crux of this video is if we're taking routes from one
routing domain and putting them into another,
we have lots of controls at that point of redistribution
regarding tagging, manipulating, which rails to bring in,
which routes to not bring in.
We can include tags as part of that mix
as we manipulate and control the routes that are brought in.
Now, some of you might be thinking, well, Keith,
this would be a lot easier if we just WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
this would be a lot easier if we just
ran OSPF in this whole domain.
I know.
But the goal of this video, these sets of videos,
is to share with you some of the techniques and tools that we
can use to control the routes in these kind of corner
situations.
So here's what we get to do.
In the next video and lab, I'm going
to walk you through setting up a mixed domain
environment with EIGRP and OSPF based on what we just
looked at, and give you a chance to practice, first
of all, the redistribution between the two
different routing protocols, and have some fun with it
as we can manipulate the metrics any way WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
as we can manipulate the metrics any way
we want to when we do that redistribution.
So I'll see you in that next hands-on lab
in just a few moments.
Meanwhile, I hope this has been informative for you.
And I'd like to thank you for viewing.