[AUDIO LOGO]
So now that our layer 3 VPN is up and running--
we have verified that just with a ping--
let's take a few minutes just to examine the routes, the labels,
and the traffic itself as it's passed through the environment
just to wrap up our understanding of how MPLS layer
3 VPN actually works.
We'll, of course, be focusing on customer A
here because, well, that's the only one we currently
have operational.
So let's go ahead and jump in and get started
with doing some verification.
So as we're jumping in, we're going
to be focusing on the path from router 6 through to router 8.
Now, of course, our core is multipathing.
So technically, this traffic could also be going this way.
We do have two paths to get there.
But this is part of what we'll be looking
at as we examine the traffic.
So, again, let's go ahead and jump in.
Let's start by taking a look at router 1.
So let's start by doing a show BGP VPNv4 unicast for the VRF
customer A. And here, we see all the routes
that are in BGP for this VRF.
Well, like I said, we're going to be focusing
on the path towards router 8.
So let's take a look at some more detail on this 10.8.8.8.
So we'll simply add that prefix to the end of our command.
If we look at our entry here, the first thing we see,
of course, is that the route extinguisher 100:10
is applied to this route.
And if we look a little bit further down,
we can see that from router 5, we
have received the label 24500 to use for this destination.
So then if we do a show MPLS forwarding table,
we can see that towards router 5,
we're going to be using either label 24403 going out interface
gigabit 0002 towards router 4 or 24302 going out gigabit 0001
towards router 3.
So it should be doing equal cost multipathic.
If we do a show IP CEG for router 5's loopback,
we can see that that's exactly what it's doing.
We have two entries here.
And both of them are being equally used.
Notice those same labels--
24403 and 24302-- are listed here as well.
Now, if we want to see what's going
to happen towards the final destination,
we can do a show IP CEF for the VRF
and then put in that destination address.
And notice what's happening.
As it goes to each next hop, the forwarding label
or the first label is going to be
either the 24403 or the 24302 like we just discussed.
Then we see the 24500 being imposed as the VPN label coming
from router 5.
And if we trace to this address from router 6,
we should see these exact labels being implemented.
So we'll trace to the 10.8.8.8 from our loopback 100
interface.
So if we take a look at the output of this trace,
we can see exactly what's happening.
First, we go to router 1 with no label.
Router 1 then multipaths on hop 2 to go between routers and 4.
Of course, when going to router 4,
it puts on the forwarding label of 403.
When going to router 3, it's putting on the label 302.
But both of them still have the same VPN label 24500.
Then we see that as it's forwarded to router 5,
it's actually doing PHP or Penultimate Hop Popping
and removing the forwarding label
but still delivering it to router 5 with the VPN label
24,500.
That label is then removed.
And the packet is delivered at hop 4 to the destination router
8 with no label.
So in this video, we took a look at the routes and the labels
in our environment that are being
used to forward the traffic.
And then we saw how those labels are being put on that traffic
here in our trace route.
So hopefully, this was a helpful exercise
to help put all of these pieces together as far
as how MPLS layer 3 VPN works.
So that concludes everything that we
need to cover in this skill, leaving us
with one more thing to do.
And that's our review in the form of a quiz.
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.