All right, next up we have a topology that's going to make sure that we
understand how
T-lock extensions are created and formed.
And so we want to pay attention to what we're trying to say here with this top
ology, which
is that we have colors that are mapped to the T-locks that belong to specific
interfaces
here.
So if we see blue, it's biz internet.
And if we see purple, that would be MPLS.
So let's dive right in.
Question number one, which two interfaces will be given T-lock extension
configuration?
Remember what we said just moments ago in the quiz.
When I want to apply the T-lock extension configuration, it does not get
applied to
a tunnel interface.
It gets applied to a layer three interface, which is going to then target,
going to target
a WAN circuit, which will have a tunnel interface on it.
And so when we say which interfaces in this environment get a T-lock extension,
it's going
to be, first of all, gig one on edge 200 and second of all, gig two on edge 201
.
So this interface here and this interface here.
So this interface on edge 200 is going to be targeting gig three and gig two
over on
the right is going to also be targeting gig three.
And that's going to allow tunnels to form through the T-lock extensions out to
the rest
of the world.
So next question, what will be the target interface?
Oh, we just answered that.
The target interface is always going to be gig three here.
So gig three will be the target for both cases.
So always make sure we understand which interface gets the config and which
interface is getting
targeted.
Number three, assume that the MPLS subnet down here has no reachability to the
internet.
What additional configuration must be entered in order to form data plane
tunnels and what
interface must be given this configuration.
So this is interesting.
We once again see that we have cloud controllers and those are attached to the
internet.
And we just said that this MPLS circuit over here doesn't have internet
connectivity.
So that's going to cause problems for this T-lock extension right here.
Well this is the T-lock extension but the interface trying to form connections
because
it's first of all going to try to form connections to the controllers.
And when it can't because there's no connectivity between these when it tries
to form a control
plane connection it can't it's not going to bother forming data plane tunnels.
So what do we do? well we have to use that max control connections command.
We have to set it to zero and we have to apply it here to our interface but
specifically
on the tunnel interface as part of that.
So once again we are forming tunnels or trying to form tunnels out this
interface through
the T-lock extension and ideally we form a tunnel down to edge 300.
But in order to form that data plane tunnel we either have to first form
control plane
tunnels which we can't or we have to have the max control connections command
set to
zero.
So lastly we want to sketch the final logical or overlay topology for this
scenario.
It's important for us to remember that the goal of SD-WAN is to establish a
logical or
overlay network.
And so we have three routers.
Well let's try to write that in there.
200, 201 and 300.
What does the logical network look like?
Well what we have is we have both of these at the same site so they're not
going to be
forming tunnels to one another.
But the 200 and 201 will be forming tunnels to 300 over the internet and they
'll be forming
these tunnels via MPLS.
So what's wonderful about this is that when I look at the overlay configuration
I don't
see any of the messiness of the underlay.
I simply see that at this location both of our edges have connectivity to the
remote
edge at the other site, edge 300.
So I don't see the fact that this connection is really winding all the way
through and doing
all kinds of crazy things.
So this is why it's so important for us to really have an emphasis on the
overlay and
understanding what it is we're building.
We're trying to build a network that's consistent and that is in a lot of ways
symmetric.
That every device has so many connections to other devices and in the end we
want to
get rid of the underlay in our minds.
We stop focusing on the physical, we look at the logical and we say this is
exactly what
we wanted and as a result this is how we can get there.
We can get there by building all of these IPsect tunnels thanks to SD-WAN and
that's
going to create an enormous amount of consistency and control over our traffic
that traverses
the WAN and we're going to see that more and more as we dive deeper into the
world of
SD-WAN.
So this is the end of the review for just bringing our network online.
It's incredible to think that we've put a lot of effort into just getting our
network
online but now we get to explore what we get to do with that network and how
that it is
online.
So that's what we'll be exploring as we move forward.
If any of the questions or any of the topology challenges caused us grief I
would recommend
going back to the recommended skill to review some of that information even
before moving
on.
Also by the way flag this skill later once you get done with the course it's a
great skill
to come back and just make sure we've got all of this information down which
will also
alert us to any maybe areas of weakness that might exist once we get to the end
of the
course.
So with all that said I hope this has been informative for you and I'd like to
thank