[AUDIO LOGO]
So now that we have auto-RP configured in our environment,
it's time to talk about redundancy.
Clearly, the rendezvous point is a single point
of failure in any sparse mode multicast environment
because without the rendezvous point,
nobody can find the sources.
So clearly, we're going to want to have redundant rendezvous
points.
And that's really not a problem with auto-RP, because that's
the job of the mapping agent.
It collects the information from all of the candidate RPs,
however many there are.
It chooses the winner.
And then it announces that winner
to everybody else on the network.
And if that winner were to go down,
it will simply choose another winner
and then announce that to everybody on the network.
So auto-RP handles this quite easily.
Now, you could also make the argument
that the mapping agent itself could
be a single point of failure.
Now, we're not going to talk about that a whole lot,
because it's actually quite a simple solution.
Simply create more than one mapping agent.
That's it.
All we have to do is make sure that those auto-RP messages--
remember the scope we set on the candidate RPs?
And we said that the candidate RP
message has to be able to make it to the mapping agent.
Yeah.
Well, you just need to make sure that it can reach
all of the mapping agents.
As long as all of the mapping agents learn about all
of the candidate RPs, well, they're
all going to make the same decision in the same way.
So you could have two mapping agents, 10 mapping agents.
It doesn't matter.
They will all come to the same conclusion
as to which candidate RP should win.
And then they'll all announce that to the network.
Doesn't matter which one I learn that
from if I'm learning the exact same information.
So redundant mapping agents, no problem.
Just configure them.
Redundant RPs, well, they're also no problem,
but let's go ahead and jump in and take a look
because what we really want to see here
is how the decision is made on the mapping agent.
So all of that said, let's bring up our topology
just real quickly to take a look at what
we're going to be configuring.
And then of course, we'll jump onto the command line,
configure our redundant RP, and see what happens.
So once again, we are still on Multicast Topology 1.
And what we already have configured, just as a reminder,
router 2 is already configured as a candidate RP for auto-RP.
And therefore, is currently, of course,
being chosen as the winner by the mapping agent, which
is currently running on router 5's loopback interface.
And what we're going to be doing in this video
is we're going to go ahead and bring router
4 back in as a redundant rendezvous point.
Or maybe it will become the primary rendezvous point.
We have to do this and see what happens.
So let's go ahead and jump into the configuration.
Clearly, we'll just start on router 4,
configuring it to be a redundant RP.
And then we'll take a look at what happens.
So in order to configure router 4 as a candidate RP,
we do have to ensure that multicast routing is
enabled on its loopback.
Now, it should be from previous configurations
that we're already on router 4.
But let's verify it.
Let's do a show pim interface.
And as we can see, loopback 0 does
in fact have multicast routing enabled on it.
So that means that router 4 should be good to go.
Let's just go into configuration mode.
We'll go into router pim for address family ipv4.
And we'll configure auto-RP.
This time, we're going to do the candidate-rp
like we did on router 2.
So candidate-rp once again off the loopback 0 interface.
We have to configure the scope.
So we'll set the scope to 16 once again.
We'll commit these changes and exit configuration.
So now let's go take a look at what's
going on, on the mapping agent.
So on router 5, the first thing to note
is we've gotten a new tunnel interface, which
again generally indicates that we've learned a new RP.
So let's do our show ip pim rp map.
And notice what's happening here on the mapping agent.
It's learning both RPs.
So it has RP 10.4.4.4 for the entire group
range learned from router 4.
It also knows about router 2 being the RP.
Info source on that one is router 2.
But notice that router 4 says, "elected via Auto-RP."
And router 2 just says, "via Auto-RP."
So it learned about both of them from auto-RP.
But router 4 has been elected.
Now, I would love to tell you that auto-RP's mapping
agent has some big fancy algorithm
that it uses to choose the winner.
But it doesn't.
It's literally choosing the rendezvous point
with the highest IP address.
That's it.
10.4.4.4 is higher than 10.2.2.2.
Therefore, router 4 wins, which really
means that as administrators, we don't really
have a lot of control over which of our redundant rendezvous
points get chosen.
Now, there's a certain argument to that
that it shouldn't matter.
If all of these RPs are equal and they can all
be chosen equally out of a pool, then it really
shouldn't matter which one the mapping agent chooses.
So to a certain extent, highest IP address
is really just almost a random choice in that
it shouldn't matter which one.
The only control we would really have as administrators
here is to change the IP addresses of the rendezvous
points.
But let's go ahead and take a look
at what this looks like on the other routers.
So for example, let's jump over to router 6.
Once again, we see that tunnel up.
And if we look at our show ip pim rp map here,
notice the only rendezvous point that router 6
knows about is router 4.
It's learned this from the mapping agent, router 5.
The reason this is so important is
because in auto-RP, the only router that knows about all
of the RPs are the mapping agents.
Now, in our case, we only have one mapping agent.
But if we had more than one, they
would all know the information.
They would all choose the RP with the highest IP address.
And that one would win.
But either way, all of the other routers
that are not mapping agents are only
going to learn about the one RP address.
Of course, we can look at any of these, and it'll be the same.
We'll just verify this in our command window.
We'll do our show ip pim rp map.
Now, of course, we just saw this on router 6.
But let's go ahead and take a look at the other routers.
So we'll just start on router 1 here.
Notice again, it knows about router 4.
And the info source is router 5, elected via auto-RP.
Router 2 here has the exact same information.
So does router 3.
So does router 4.
We've, of course, already looked at 5 and 6.
So here on router 7, we see that it knows the same information
as well.
And just as some final verifications,
if we do a show ip mroute, we see here for the star comma G
tree that the RP is 10.4.4.4.
So clearly, it's using the correct RP for the star comma G
trees.
By the way, also notice this S comma G group down
at the bottom.
This is, of course, the auto-RP group now having
a proper source of router 5, which is the mapping agent,
because remember that the 224.0.1.40 is the group used
by the mapping agent to tell everybody else
who the rendezvous point is.
So it makes sense that the mapping agent
is the source for that group.
And one final verification, just to make
sure our traffic is still flowing,
we'll do our mroute count.
We see that currently, there are 279 packets that have been
forwarded on the source tree.
We give it a second and do it again.
It's now 284.
So once again, all of the traffic
is being forwarded properly by the data plane
through our environment with our redundant RP candidates.
So in this video, we configured router 4
to be, well, a redundant RP.
But as we saw, since it has a higher IP address,
it actually ended up taking over as the active RP.
And router 2 actually became the standby or redundant RP
in this particular environment.
And again, that decision is solely
made based on the higher IP address of the candidate RPs.
Remember that decision is made on the mapping agent.
The mapping agent, as we saw, is the only router
that's aware of all of the candidate RPs.
Router 5 knew about router 2 and router 4.
But all of the other routers only knew about router 4
after the mapping agent had made its decision.
So this is pretty much sums up how auto-RP works.
However, there is another option when
it comes to automatically learning the RP's address.
And that is Bootstrap Router, or BSR.
And that's exactly what we're going to take a look at next.
Till then, I hope this has been informative for you,
and I'd like to thank you for viewing.