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[AUDIO LOGO]

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So now that we have auto-RP
configured in our environment,

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it's time to talk
about redundancy.

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Clearly, the rendezvous
point is a single point

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of failure in any sparse
mode multicast environment

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because without the
rendezvous point,

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nobody can find the sources.

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So clearly, we're going to want
to have redundant rendezvous

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points.

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And that's really not a problem
with auto-RP, because that's

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the job of the mapping agent.

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It collects the information
from all of the candidate RPs,

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however many there are.

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It chooses the winner.

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And then it
announces that winner

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to everybody else
on the network.

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And if that winner
were to go down,

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it will simply
choose another winner

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and then announce that to
everybody on the network.

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So auto-RP handles
this quite easily.

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Now, you could also
make the argument

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that the mapping
agent itself could

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be a single point of failure.

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Now, we're not going to
talk about that a whole lot,

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because it's actually
quite a simple solution.

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Simply create more
than one mapping agent.

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That's it.

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All we have to do is make sure
that those auto-RP messages--

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remember the scope we
set on the candidate RPs?

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And we said that
the candidate RP

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message has to be able to
make it to the mapping agent.

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Yeah.

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Well, you just need to
make sure that it can reach

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all of the mapping agents.

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As long as all of the mapping
agents learn about all

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of the candidate
RPs, well, they're

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all going to make the same
decision in the same way.

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So you could have two mapping
agents, 10 mapping agents.

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It doesn't matter.

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They will all come to
the same conclusion

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as to which candidate
RP should win.

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And then they'll all
announce that to the network.

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Doesn't matter which
one I learn that

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from if I'm learning the
exact same information.

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So redundant mapping
agents, no problem.

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Just configure them.

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Redundant RPs, well,
they're also no problem,

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but let's go ahead and
jump in and take a look

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because what we really
want to see here

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is how the decision is
made on the mapping agent.

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So all of that said, let's
bring up our topology

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just real quickly to
take a look at what

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we're going to be configuring.

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And then of course, we'll
jump onto the command line,

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configure our redundant
RP, and see what happens.

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So once again, we are still
on Multicast Topology 1.

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And what we already have
configured, just as a reminder,

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router 2 is already configured
as a candidate RP for auto-RP.

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And therefore, is
currently, of course,

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being chosen as the winner
by the mapping agent, which

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is currently running on
router 5's loopback interface.

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And what we're going to
be doing in this video

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is we're going to go
ahead and bring router

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4 back in as a redundant
rendezvous point.

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Or maybe it will become the
primary rendezvous point.

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We have to do this
and see what happens.

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So let's go ahead and jump
into the configuration.

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Clearly, we'll just
start on router 4,

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configuring it to
be a redundant RP.

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And then we'll take a
look at what happens.

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So in order to configure
router 4 as a candidate RP,

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we do have to ensure
that multicast routing is

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enabled on its loopback.

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Now, it should be from
previous configurations

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that we're already on router 4.

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But let's verify it.

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Let's do a show pim interface.

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And as we can see,
loopback 0 does

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in fact have multicast
routing enabled on it.

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So that means that router
4 should be good to go.

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Let's just go into
configuration mode.

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We'll go into router pim
for address family ipv4.

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And we'll configure auto-RP.

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This time, we're going
to do the candidate-rp

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like we did on router 2.

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So candidate-rp once again
off the loopback 0 interface.

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We have to configure the scope.

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So we'll set the scope
to 16 once again.

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We'll commit these changes
and exit configuration.

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So now let's go take
a look at what's

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going on, on the mapping agent.

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So on router 5, the
first thing to note

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is we've gotten a new
tunnel interface, which

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again generally indicates
that we've learned a new RP.

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So let's do our
show ip pim rp map.

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And notice what's happening
here on the mapping agent.

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It's learning both RPs.

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So it has RP 10.4.4.4
for the entire group

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range learned from router 4.

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It also knows about
router 2 being the RP.

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Info source on that
one is router 2.

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But notice that router 4
says, "elected via Auto-RP."

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And router 2 just
says, "via Auto-RP."

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So it learned about both
of them from auto-RP.

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But router 4 has been elected.

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Now, I would love to tell
you that auto-RP's mapping

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agent has some big
fancy algorithm

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that it uses to
choose the winner.

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But it doesn't.

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It's literally choosing
the rendezvous point

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with the highest IP address.

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That's it.

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10.4.4.4 is higher
than 10.2.2.2.

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Therefore, router 4
wins, which really

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means that as administrators,
we don't really

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have a lot of control over which
of our redundant rendezvous

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points get chosen.

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Now, there's a certain
argument to that

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that it shouldn't matter.

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If all of these RPs are
equal and they can all

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be chosen equally out of
a pool, then it really

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shouldn't matter which one
the mapping agent chooses.

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So to a certain extent,
highest IP address

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is really just almost
a random choice in that

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it shouldn't matter which one.

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The only control we would
really have as administrators

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here is to change the IP
addresses of the rendezvous

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points.

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But let's go ahead
and take a look

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at what this looks like
on the other routers.

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So for example, let's
jump over to router 6.

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Once again, we see
that tunnel up.

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And if we look at our
show ip pim rp map here,

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notice the only rendezvous
point that router 6

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knows about is router 4.

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It's learned this from the
mapping agent, router 5.

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The reason this
is so important is

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because in auto-RP, the only
router that knows about all

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of the RPs are the
mapping agents.

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Now, in our case, we only
have one mapping agent.

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But if we had more
than one, they

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would all know the information.

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They would all choose the RP
with the highest IP address.

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And that one would win.

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But either way, all
of the other routers

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that are not mapping
agents are only

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going to learn about
the one RP address.

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Of course, we can look at any
of these, and it'll be the same.

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We'll just verify this
in our command window.

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We'll do our show ip pim rp map.

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Now, of course, we just
saw this on router 6.

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But let's go ahead and take
a look at the other routers.

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So we'll just start
on router 1 here.

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Notice again, it
knows about router 4.

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And the info source is router
5, elected via auto-RP.

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Router 2 here has the
exact same information.

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So does router 3.

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So does router 4.

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We've, of course, already
looked at 5 and 6.

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So here on router 7, we see that
it knows the same information

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as well.

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And just as some
final verifications,

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if we do a show ip mroute, we
see here for the star comma G

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tree that the RP is 10.4.4.4.

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So clearly, it's using the
correct RP for the star comma G

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trees.

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By the way, also notice
this S comma G group down

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at the bottom.

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This is, of course, the
auto-RP group now having

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a proper source of router 5,
which is the mapping agent,

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because remember that the
224.0.1.40 is the group used

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by the mapping agent
to tell everybody else

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who the rendezvous point is.

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So it makes sense
that the mapping agent

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is the source for that group.

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And one final
verification, just to make

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sure our traffic
is still flowing,

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we'll do our mroute count.

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We see that currently, there
are 279 packets that have been

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forwarded on the source tree.

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We give it a second
and do it again.

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It's now 284.

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So once again,
all of the traffic

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is being forwarded
properly by the data plane

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through our environment with
our redundant RP candidates.

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So in this video, we
configured router 4

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to be, well, a redundant RP.

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But as we saw, since it
has a higher IP address,

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it actually ended up taking
over as the active RP.

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And router 2 actually became
the standby or redundant RP

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in this particular environment.

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And again, that
decision is solely

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made based on the higher IP
address of the candidate RPs.

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Remember that decision is
made on the mapping agent.

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The mapping agent, as we
saw, is the only router

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that's aware of all
of the candidate RPs.

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Router 5 knew about
router 2 and router 4.

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But all of the other routers
only knew about router 4

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after the mapping agent
had made its decision.

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So this is pretty much
sums up how auto-RP works.

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However, there is
another option when

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it comes to automatically
learning the RP's address.

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And that is Bootstrap
Router, or BSR.

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And that's exactly what we're
going to take a look at next.

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Till 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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