It's time.
Time for what?
Time to plan out the network topology
that could help us test the OSPF path preference.
[MUSIC PLAYING]
So here's the challenge that we want to prove out.
And that is if an OSPF router.
Let's pick on R3.
if it receives the exact same route for the SEC same prefix.
Let's say it's the 123.0.0.0 network with a /24,
for that one network, let's imagine that it receives it
as an OSPF intra-area route. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
as an OSPF intra-area route.
And let's also imagine it receives
that as an inter-area route.
And let's also imagine it receives it
as an external type 1 and an external type 2,
and also from a not-so-stubby area,
and a type 1 and also a not-so-stubby area type 2.
So if-- let's see, how many is that?
1, 2, 3, 4, 5.
1, 2, 3, 4, 5, 6.
So this probably is not going to happen to a production network
but it does give us a chance to prove WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
but it does give us a chance to prove
or figure out based on the type of OSPF route
for that 123 network, which one the router will
put into its routing table and go ahead and then use.
So here's what I'd like to do.
If we want these types of routes,
I propose we do it for this network, the 123 network
with an 8-bit mask.
Oh, you know what?
Let's do 8 bits.
You know why?
It's like, why do 8 bits instead of 24?
Less typing.
So they'll save us a few 255's along the way.
So for this OSPF network, currently I've
area 0 here and area 1 here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
area 0 here and area 1 here.
To make this work, we're going to need
some not-so-stubby areas.
So let's make area 1 a not-so-stubby area.
So we'll tell R3, who is the AVR,
and R5 and R7 that area 1 is a not-so-stubby area.
That will allow us to do injections here,
so we could inject, redistribute routes
into that not-so-stubby area, and then we
can inject them as type 1s or type twos
in that not system area
and for externals what we could do is we
could go up to the backbone.
On the backbone, we could go on some routers WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
On the backbone, we could go on some routers
and do redistribution into OSPF.
And those would come in as external.
And then we can specify with the redistribution
those static routes are coming in as type 1 or type 2.
And then, for the intra-area route,
we could just create a loopback, for example, on R1
and add a loopback with the 123 address, make it
an intra-area route.
That's going to be a good exercise for us,
not just in the actual testing of the OSPF path preference,
but also in implementing these different redistributions WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
but also in implementing these different redistributions
and area types as a good practice in working with OSPF.
And then, together, we can configure the topologies
so that all those different route types show up.
I'll walk you through it step by step.
And then, with all of them present, we'll
take a look at R3 and say, which one do you choose?
And we're going to find out the first ones
can be the intra-area route is always preferred regardless
of the metric.
It's going to want the intra area route for that 123.
And if there's no intra-area route,
it's going to then want the inter-area route.
And if that's not present, hmm, then it WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And if that's not present, hmm, then it
gets interesting with the rest of these.
So we'll have a chance to lab it up and prove it out
in the lab starting in the next video.
So without further ado, I'll see you
in that video in just a few moments, where
we'll lab this up.
Meanwhile, I hope this has been informative for you
and I'd like to thank you for viewing.