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[AUDIO LOGO]

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So now it's time to jump
onto the command line

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and actually implement
bidirectional

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PIM in our environment.

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However, before
we can do that, we

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are going to have
to make a change

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to our current environment.

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Right now, we are
using anycast RP.

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And of course, the main
idea behind anycast RP

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is the rendezvous points
are essentially acting

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in an active-active role.

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This is why we had to
have MSDP to cluster

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or synchronize the rendezvous
points so that they

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would know all the information.

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That's fine for
the control plane.

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That's no problem.

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But we can't have multiple
active RPs in the data plane.

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That simply doesn't work.

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Now, with bidir PIM, can we
still have redundant RPs?

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Yes, of course we can.

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But it has to be an
active-standby scenario,

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sort of like what we can
do with auto-RP or BSR,

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changing priorities.

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However, we can't have
them active-active.

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So the first thing
we're going to do

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is disable anycast RP
in the environment.

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Then we'll change our tree
over to be bidirectional.

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We will have to stop our
current traffic flow to allow

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the current route to time out.

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That way, it can get rebuilt
as a bidirectional tree.

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So let's take a
look at our topology

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just real quickly so we know
exactly what we're doing.

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And then we'll jump
into the command line

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and make all of this happen.

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So for this demonstration,
we will still

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be on Multicast Topology 2.

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Just as a reminder, that
means all of our routers

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are running IOS XE.

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And what we're going to be doing
is configuring our environment

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so that only router 2 is the RP.

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Now, we'll go ahead and
keep the current address

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we have on there
of the 100.1.1.1,

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using its loopback
100 interface.

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However, we will
be unconfiguring

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all of that
information on router 4

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as well as taking down the
MSDP peering between router 2

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and router 4.

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Once that's done, we will verify
that our environment is still

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working.

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And then we'll convert
everything over to bidir

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and take a look at what that
changes in the environment

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as far as which
devices are actually

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in the forwarding path.

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So let's go ahead
and get started.

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We'll begin by
reconfiguring router 4.

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So the first thing we want
to do here on router 4

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is configure it not
to be an RP candidate.

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So we'll start with the
no ip pim rp-candidate

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on the loopback 100 interface.

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Since we're not using
loopback 100 anymore,

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we can also say no
interface loopback 100.

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That's no longer needed.

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And we want to take down the
MSDP peering with router 2

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as well.

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So we'll simply say no
ip msdp peer 10.2.2.2.

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We can exit configuration.

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And then we'll go make our
modifications on router 2

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as well.

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So we see that router 2
knows that the MSDP peering

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session is already going down.

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So all we really need
to do on this side

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is remove that configuration.

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We'll simply say, no
ip msdp peer 10.4.4.4.

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Everything else on router
2 can stay the same

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because as it's still
going to be an RP.

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And it's still going to use
its loopback 100 interface.

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Let's go over to the BSR.

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And let's do a
show ip pim rp map.

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And we see that we still
know the RP as 100.1.1.1.

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And we're learning that
information from 100.1.1.1.

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Problem is since that
was an anycast address,

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there's no real way to verify
that that's router 2 and not

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still router 4,
except for the uptime.

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Notice the uptime on
this is only 42 seconds.

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So it's a pretty good
indicator that this information

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is coming strictly from
router 2 at this point.

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And this is new information.

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So that said, let's go ahead and
verify that our environment is

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still functional before
we switch this over

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to bidirectional.

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To do that, let's go ahead and
start our ping on router 10.

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And we'll verify that
that traffic is actually

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getting to router 8.

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We'll do that, of course,
by verifying router 7.

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We'll start with
a show ip mroute.

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It should have the
S comma G entry.

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We can see here that it does.

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If it didn't have the S
comma G entry, of course,

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that pretty much indicates that
the first packet didn't even

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get to router 7, but it has.

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So if we do our show
ip mroute count,

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we can see that it's
currently forwarded 19 packets

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down the source-based tree.

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And again, we give
it a few seconds.

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Look at it again.

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And we can see that now
it has forwarded 24.

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So clearly, it is forwarding
packets, and it is working.

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Now, what we don't want
is all of this information

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to stay here as we
switch over to bidir.

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So there's two
things we have to do

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to allow all these routing
entries to time out.

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First, we're, of course, going
to have to stop the source.

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So let's go back over to
router 10 and shut this down.

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And we want the star comma
G to time out as well.

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So now let's go over to
router 8, go into its gigabit

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1 interface.

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And say, no ip igmp
join 224.1.1.1.

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We want to take this
out of the group.

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At this point, we
want to let all

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of the multicast routes
on all of the devices time

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out or go around and
clear all the tables.

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So at this point, we'll just
forward until they time out.

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So now we've given it a moment.

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Let's hop over here to router 2.

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And let's do a show ip mroute.

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And what we see
is all that's left

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is that default auto-RP group,
which is perfectly fine.

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So now what we need to do
is configure everything

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for bidirectional PIM.

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So the first thing we need
to do is enable the feature

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on all the routers.

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The way we do this is we simply
go into configuration mode.

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We type ip pim bidir-enable.

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That's all we have to do.

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So we'll go ahead and paste
that in here on router 1.

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We just did router 2, router 3,
router 4, router 5, router 6,

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and last but not
least, router 7.

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So now all of our
devices have been enabled

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to support bidirectional PIM.

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The next thing we have to
do is configure the RP so

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router 2 to advertise
itself as a bidir RP.

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So on the ip pim
rp-candidate line,

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where we're advertising
our loopback 100,

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we simply have to add bidir
to the end of this statement.

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We'll go ahead and hit Enter.

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We can exit configuration.

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We'll give this just a
few seconds to propagate.

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And then all of the
devices should then

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be aware that router 2 is a
bidir-capable rendezvous point.

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So let's use our
chat window here.

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We'll do a show ip pim rp map.

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Notice that here on
router 2, it's now

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added bidir to the end
of the RP statement.

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All of the other routers
should know this as well.

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Let's hop over to router 1.

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We see router 1 also
has the bidir statement.

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So let's just verify
all of them quickly.

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Router 3 has it.

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Router 4 has it.

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So does router 5,
router 6, and router 7.

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So all of our
PIM-enabled routers

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are aware that the
RP is 100.1.1.1

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and it is bidir capable.

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Just a quick note here
on the bidir statement--

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this can also be put on the
line, advertising a candidate

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RP into auto-RP as well.

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Or if we are doing static RP
assignment, on the static RP

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line, there is also
a place to put bidir.

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So regardless of how we're
learning about the RP,

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there is a choice to configure
bidir on every option.

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We just happen to be using BSR
right now in our demonstration.

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So now that all
of the routers are

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aware of the
bidir-capable RP, let's

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go back over to router
8 and rejoin our group.

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So we'll simply take the
"no" off the beginning here.

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Join the group again.

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We can exit configuration.

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Let's go back to router 10
and start our ping again

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so we have a source.

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And as usual, let's go
back over to router 7

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and see if we're getting
the S comma G entry.

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So if we do our show
ip mroute, notice

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there's no S comma G entry,
because this is bidir PIM.

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We shouldn't have one.

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Remember, in bidir, everything
is going to be a shared tree.

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So notice, instead,
what we have is

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first we have a
flag on there, which

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is the capital B, indicating
that this is a bidir group.

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We can also see that we
have a bidir upstream, which

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is sort of like the incoming
interface, so to speak,

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except with bidir,
of course, we see

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that the same
interface, gigabit 2,

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can be both bidir upstream as
well as an outgoing interface.

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But the upstream is always going
to be towards the rendezvous

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point.

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That's what the RPF check
is going to be for here.

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So we see that
the bidir upstream

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is gigabit 2 towards router 3.

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And then the outgoing
interfaces are both interfaces

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gigabit 3 and gigabit 2
because we can, of course,

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forward traffic in
both directions.

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If we do a show ip
mroute count, notice

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that again, there's no source
tree listed here anymore.

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It's just the RP tree.

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It has forwarded
59 packets so far.

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And if we hit Up, we can
see that it's now 64.

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So once again, the
environment is working,

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and we are forwarding traffic.

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However, let's take
a look at this tree

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just a little bit more.

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So let's, for example, look at
the rendezvous point, router 2.

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Let's do a show ip mroute here.

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Once again, what do we see?

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Well there's no S comma Gs.

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We see that our group
has the B flag on it.

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We see that the bidir upstream
is null because remember,

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the incoming interface
on the rendezvous point

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is always null.

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But notice, on the
outgoing interface list,

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we right now just
have gigabit 2.

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That's currently
the only direction

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that we've received
the join from.

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Let's also take a look
at the first-hop router.

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So let's look at router 6.

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So notice, on the
first-hop router,

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it is, of course, still
flagged as bidirectional.

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But notice, it's not even
for our specific group,

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because that join hasn't
actually come here.

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We haven't gotten a star comma G
join for that particular group,

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224.1.1.1.

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What it has done
is it has received

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the traffic going to 224.1.1.1.

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It did a show ip pim rp map.

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And what did it find out?

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For that group, the
RP is 100.1.1.1.

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So it did the RPF check
that says to go to router 1,

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50.0.16.1, as the RPF neighbor.

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And it forwards up the tree
using the bidir upstream,

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gigabit 1, towards router 1.

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So that's how this works
on both sides of the tree

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as well as on the
rendezvous point.

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So in this video, we set up
and configured bidir PIM.

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And as we saw, a
lot of the battle

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here was just getting
everything cleared out,

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then enabling bidir PIM
on all of the routers,

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setting bidir on
the RP announcement.

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And again, that can be done
either through BSR, auto-RP,

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or static RP assignment.

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We just have to add
bidir to the end.

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What's interesting,
by the way, is

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if you have not enabled
bidir on that router

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yet, that command
doesn't even show up.

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So you'll actually think you're
looking in the wrong place.

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You have to enable bidir
on the router first.

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Then you get that option on
the RP announcement line.

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Now, once everybody
knew about the bidir RP,

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we started up our source.

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We started up our receiver.

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And the traffic flowed through
just as it normally would,

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except there was
no SPT switchover.

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Everything flowed through
the rendezvous point.

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We had no S comma G entries
in any of our routing tables.

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Everything was star comma
G. And also remember

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that on the upstream
side of our tree,

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it didn't even go to
the specific group.

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It just used the
general RP mapping

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to know which way to send the
traffic up the shared tree.

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So all of this is pretty cool.

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But we have another cool
feature we have to look at--

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source-specific multicast.

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And in a way, it's almost
the opposite of bidir PIM,

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but not exactly.

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We're going to cover that 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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