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[AUDIO LOGO]

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Hello, and welcome to
Implementing L3 VPN

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advanced features.

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So we've already gone
through all the basics

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of getting L3 VPN up and
running in our environment.

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But now, we want to
jump in and take a look

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at some modifications that we
can make to this environment,

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if we have a need to do so.

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So the first thing
we're going to do

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is jump in and take a closer
look at penultimate hop-popping

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or PHP operation.

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This is where the
next to last router

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actually removes the forwarding
label because the egress PE

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theoretically doesn't
need that forwarding label

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to get to its own loopback.

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This can, however, have some
unintended consequences.

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So we're going to
look at those details.

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Then we're going to take
a look at TTL propagation.

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When a packet comes in
to the MPLS environment,

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the default behavior
is to copy the TTL

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from the original packet
onto the newly created label.

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This is not always
desirable behavior, however,

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because if a customer does a
trace through our environment,

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they'll get to see all of
the P routers in our core,

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and that might not be desirable.

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Then, we'll take a look at
something called route leaking.

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There are occasions, where we
might need routes to actually

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go from one VRF to
another, either maybe

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between customers or between
different departments

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at a company, maybe.

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Or it would also be another
way to possibly implement

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central service VPNs.

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So there's a couple of reasons
we might want to do this,

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but we're going to want to do
it in a controlled fashion.

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And finally, we'll wrap up with
looking at conditional label

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advertisement or what we would
generically call label control.

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We'll take a look at
how we can control

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which labels get advertised
to peers for which prefixes,

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as well as which
labels we're accepting

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for which prefixes from peers.

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So again, we can either
filter outbound or inbound.

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So as you can hear, we've
got some pretty cool stuff

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to cover here.

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Hopefully, you'll find
this entertaining.

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Let's go ahead and jump in
and get started configuring

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all of these things.

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And I'll see you
in the next video.

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