[MUSIC PLAYING]
So now that we have all of our infrastructure
in our core set up to receive, process, keep separated all
of the customer routes, get them through our network,
and send them out to the other customer
sites on the remote ends, it would be very, very helpful
at this point if the customers were actually
sending us routes.
And to do that of course, we're going
to use a CE-PE routing protocol.
Now, the majority of routing protocols are supported here.
It really comes down to which protocols
the service provider is going to choose to support.
The majority support BGP, and only BGP.
I know there are a few out there that support OSPF.
I'm not really aware of any that support other protocols,
but I'm sure that they may exist.
So let's go ahead and jump in and talk
about how this works, how it fits into the big picture,
and take a look at some of those details.
So we are going to have a routing protocol running
between the CE and the PE, most commonly called
the CE-PE routing protocol.
Now for this, as we mentioned, most protocols are supported.
That would include static routing, OSPF, BGP, EIGRP,
IS-IS, RIP version 2.
Now be aware that the odd protocol out here is static.
Static is not exactly a protocol.
And this one would be implemented, really,
just on the service provider side,
with a static route pointing to the customers networks,
and then redistributing that into BGP.
Now, the customer would also, of course,
have to have a static route pointing to the service
provider.
But this isn't exactly a protocol that's running here.
But from the service provider standpoint,
we would treat it the same way.
Now, each of these protocols has its own caveats
that have to be addressed.
And we'll address those more as we get to implementation.
Because some of those caveats are not small topics.
So we will get to that in more detail.
Now, since we're using multi-protocol BGP exclusively
in the core, this CE-PE protocol is
going to have to do redistribution,
unless we're actually using BGP towards the customer.
Any other protocol would have to be redistributed.
Let's jump over to our diagram, and take a look
at how this whole thing fits together.
So let's start with customer A. And let's say
we decide to run OSPF with customer A.
This does not have to be the same at both sides, by the way,
but it most commonly would be.
Here is the issue.
Since we're running OSPF with the customer,
but we're running BGP to exchange the routes
through the core, this means that in the VRF
we are going to have to do mutual redistribution
between OSPF and BGP.
Just indicate that with a little circle arrow
there, indicating mutual redistribution.
Now, this is not a problem.
It's how it's designed to work.
But just be aware that this is another step we
would have to take on the PE.
Where, on the other hand, if customer B is running BGP,
specifically eBGP, we don't have to do
any redistribution for VRF B. So this saves us
a lot of work on the PE.
It means we're only running one protocol,
and we don't have to do any redistribution, which
is why this is generally the preferred method.
Now, that does not mean that no redistribution is happening.
Because chances are, customer B is running OSPF inside
of their own network.
What that means is it's the CE that's
going to be doing the mutual redistribution between BGP
and OSPF.
We would, of course, have to do this on both sides.
So this is really an example of how
the two most popular choices, BGP and OSPF,
would work as the CE-PE.
So in this video, we just took a look at some information
about the CE-PE protocol.
We talked about how, although most protocols are supported
here, the most popular by far is BGP,
with a small handful of providers
possibly still supporting OSPF, and probably
not many at all supporting other protocols.
So this is all we need to cover in this skill.
That leaves us with nothing else except for a 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.