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[MUSIC PLAYING]

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So now that we have all
of our infrastructure

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in our core set up to receive,
process, keep separated all

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of the customer routes, get
them through our network,

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and send them out to
the other customer

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sites on the remote ends, it
would be very, very helpful

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at this point if the
customers were actually

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sending us routes.

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And to do that of
course, we're going

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to use a CE-PE routing protocol.

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Now, the majority of routing
protocols are supported here.

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It really comes down
to which protocols

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the service provider is
going to choose to support.

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The majority support
BGP, and only BGP.

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I know there are a few out
there that support OSPF.

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I'm not really aware of any
that support other protocols,

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but I'm sure that
they may exist.

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So let's go ahead
and jump in and talk

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about how this works, how it
fits into the big picture,

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and take a look at
some of those details.

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So we are going to have a
routing protocol running

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between the CE and the
PE, most commonly called

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the CE-PE routing protocol.

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Now for this, as we mentioned,
most protocols are supported.

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That would include static
routing, OSPF, BGP, EIGRP,

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IS-IS, RIP version 2.

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Now be aware that the odd
protocol out here is static.

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Static is not
exactly a protocol.

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And this one would be
implemented, really,

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just on the service
provider side,

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with a static route pointing
to the customers networks,

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and then redistributing
that into BGP.

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Now, the customer
would also, of course,

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have to have a static route
pointing to the service

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provider.

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But this isn't exactly a
protocol that's running here.

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But from the service
provider standpoint,

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we would treat it the same way.

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Now, each of these protocols
has its own caveats

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that have to be addressed.

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And we'll address those more
as we get to implementation.

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Because some of those
caveats are not small topics.

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So we will get to
that in more detail.

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Now, since we're using
multi-protocol BGP exclusively

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in the core, this
CE-PE protocol is

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going to have to
do redistribution,

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unless we're actually using
BGP towards the customer.

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Any other protocol would
have to be redistributed.

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Let's jump over to our
diagram, and take a look

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at how this whole
thing fits together.

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So let's start with
customer A. And let's say

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we decide to run
OSPF with customer A.

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This does not have to be the
same at both sides, by the way,

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but it most commonly would be.

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Here is the issue.

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Since we're running
OSPF with the customer,

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but we're running BGP
to exchange the routes

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through the core, this
means that in the VRF

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we are going to have to
do mutual redistribution

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between OSPF and BGP.

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Just indicate that with
a little circle arrow

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there, indicating
mutual redistribution.

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Now, this is not a problem.

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It's how it's designed to work.

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But just be aware that
this is another step we

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would have to take on the PE.

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Where, on the other hand, if
customer B is running BGP,

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specifically eBGP,
we don't have to do

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any redistribution for
VRF B. So this saves us

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a lot of work on the PE.

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It means we're only
running one protocol,

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and we don't have to do
any redistribution, which

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is why this is generally
the preferred method.

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Now, that does not mean that
no redistribution is happening.

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Because chances are, customer
B is running OSPF inside

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of their own network.

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What that means is
it's the CE that's

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going to be doing the mutual
redistribution between BGP

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and OSPF.

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We would, of course, have
to do this on both sides.

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So this is really
an example of how

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the two most popular
choices, BGP and OSPF,

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would work as the CE-PE.

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So in this video, we just took
a look at some information

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about the CE-PE protocol.

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We talked about how, although
most protocols are supported

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here, the most
popular by far is BGP,

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with a small
handful of providers

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possibly still supporting
OSPF, and probably

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not many at all supporting
other protocols.

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So this is all we need
to cover in this skill.

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That leaves us with nothing
else except for a review

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in the form of a quiz.

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And that's exactly what
we're going to do next.

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Until then, I hope this has
been informative for you,

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and I'd like to thank
you for viewing.

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