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[AUDIO LOGO]

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Our next choice for
automatically discovering

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the RP address is the
industry standard BSR,

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or Bootstrap Router.

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Now, this functions in a lot
of ways similar to AutoRP.

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But it has its fundamental
differences as well.

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Like AutoRP, this has
two primary components.

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We have the routers that
are the RP candidates that

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are willing to be RPs for
either all of the groups

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or maybe just a
subset of the groups.

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Then those announce their
willingness to the--

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well, the bootstrap router,
not the mapping agent like we

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had in AutoRP.

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But, here, we call it the BSR.

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So the protocol
itself is actually

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named after that
particular router.

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Now, it has a very similar job.

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It collects all the information
about the candidate RPs.

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But here's a
fundamental difference

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where AutoRP chose one RP
chosen by the mapping agent

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and announced to the
rest of the network.

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In BSR, the entire
list of candidate RPs

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is collected on the BSR.

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And then the whole list is sent
out to all the other routers.

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And then each of those
choose the RP off that list.

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Now, they're all going to
choose in the same way.

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So, ultimately,
we're still going

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to end up with everybody
choosing the same RP.

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It's just done a
little bit differently.

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As we go through, we'll see why.

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This is to allow a form of load
sharing that we can do in BSR.

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Now, of course, another
fundamental difference here

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is this is actually
built into PIM itself.

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It actually uses PIM's multicast
group for its communication.

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We don't have these
additional groups,

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like we did with
AutoRP, that have

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to be sent through the network.

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So that's a big advantage.

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But it also means it's only
supported in PIM version 2.

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So, again, it has a lot
of similarities, but also

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quite a few differences.

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So let's go ahead
and jump in and talk

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about those differences
and similarities.

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And then we'll jump
into the command line

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and take a look
at BSR in action.

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So as we mentioned, BSR is
the industry standard version

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of AutoRP.

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This is defined
in RFC 5059 if you

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want to look at this in
a little bit more detail.

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We also mentioned that this
is part of PIM version 2.

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This is not available
in PIM version

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1, because PIM had to be
updated in order to support BSR.

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Now, this actually uses
the PIM group itself.

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So this is traveling right
inside of 224.0.0.13.

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The big advantage
to this, of course,

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is this is a
link-local multicast

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group, which means it doesn't
have to be routed itself.

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So this does not have that
same problem that AutoRP did.

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This travels right inside
the PIM protocol itself.

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So we don't have to have
any additional multicast

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groups that are being
flooded through the network.

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So, again, from an
operational perspective,

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the BSR actually
collects the information

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about those candidate RPs.

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Now, of course,
the candidate RPs

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still have to announce
their willingness

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to be an RP to the BSR.

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But you can see here how
the BSR is essentially

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acting the same as the
mapping agent did in AutoRP.

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Where it gets to be a
little bit different

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is the BSR then disseminates all
of the candidate RP information

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to the other routers.

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It doesn't just
choose one winner.

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The BSR's job is not
to select the RP.

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It simply collects
the information

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and then sends it out to
all of the other routers.

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Each of those other
routers then makes

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its own independent decision.

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But it is based
on the same rules.

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Since it's based
on the same rules,

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they will all make the same
although independent decision.

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This is important
because we have

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to understand that we're
still going to learn

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the same RP on each device.

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Now, these rules can be
modified by the BSR itself.

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We'll see how to do that when
we get into configuration.

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This uses something
called a hash mask.

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And we can use this to implement
some load sharing in BSR.

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Now, just so we're
clear, we're not

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going to get very deep
into that load sharing here

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in this skill.

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However, when we
get to our skill

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on actually
implementing multicast

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and we have a larger environment
that we're working with,

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we'll take a look
at this and see

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how BSR can choose different
RPs for different groups

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based on this hash mask.

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So because of the way
all of this works,

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this does give us a way
to provide redundancy

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because, again, the BSR will
announce multiple candidates,

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mobility because, again,
any of those addresses

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can move or be
added to the group

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or removed from the group.

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And it allows us to do that
group-based load sharing we

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were just talking about
based on the hash mask that's

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announced by the BSR.

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So now that we have
some of these details

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down, let's jump
into the command line

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and take a look how
to actually configure

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BSR to be a candidate RP as well
as configuring the BSR itself.

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So let's begin with
a show ip pim rp map.

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We currently have no
groups mapped to any RPs.

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However, if we do
a show ip mroute,

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we will see that we,
of course, are still

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listening to the AutoRP group.

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But the main thing
we want to see

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is that we're not
going to be adding

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to this when we start up BSR.

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Also, if we did a show ip igmp
groups, we'll see once again,

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we're joined to
that AutoRP Group

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on our loopback interface.

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However, we're not
going to be adding

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to this as we start up BSR.

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That's the main
thing we want to see

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is that this traffic is just
going to be inside of PIM

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itself.

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So let's go into
configuration mode.

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First thing we'll do
is configure ourselves

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to be the RP candidate.

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The command for this is
a little bit different.

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It's ip pim.

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And this time it's
just rp-candidate.

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Once again, we have to
specify the interface base.

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So we'll say loopback 0.

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Now, notice that there's
nothing on here about scope.

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The reason scope is not
here is because this is

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all link-local multicast now.

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It's not being routed, so
there is no need for a TTL.

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The TTL is going to be 1.

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Also note that we can, again,
configure the group list here,

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just like we did with
static and AutoRP.

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We can also change the interval.

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And we can set the priority
because, again, BSR

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is going to follow rules as far
as which candidate to select.

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Again, we're not going to change
any of these for this example.

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So we'll just go
ahead and hit Enter.

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Now, if we do a
show ip pim rp map,

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notice that, again, we still
haven't learned anything yet,

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because we don't have a BSR.

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However, we are
being a candidate RP.

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Also note it's indicating
that this is only for PIM

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version 2 because
that's what BSR needs.

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So now let's configure this
router to also be the BSR.

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So now we say ip
pim bsr-candidate.

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Quick note here, the reason
why this is a candidate,

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we can also have redundant BSRs.

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And it will elect one BSR out of
the group to actually function

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as the active BSR.

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This is going to be done
by priority as well.

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And we'll see that here as
we go through this command.

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If we take a look
at our options,

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it's again just
for the interface.

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So we'll say loopback 0.

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And here's where we can
set that hash mask length.

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Now, the default for
this is going to be 0.

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And we'll leave it
like that for now.

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Notice I could also hit Enter
and go with the defaults.

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The only reason I'm going to
put in the actual 0 and continue

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is this is where we could
set the priority as far

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as whether we're allowed to
become the active bootstrap

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router.

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So we could configure
the priority as well.

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Now, again, we're not
going to configure these.

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However, I just
wanted to point out

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that notice you have to put the
hash mask length before you can

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specify the priority, or
you can specify none of them

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and just get the defaults.

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Notice that our
tunnels have already

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come up, indicating that this is
probably working just fine now.

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We'll exit configuration.

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And we'll do a
show ip pim rp map.

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So what do we see?

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First, we see that this router
is the bootstrap router.

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It's, again, responsible for
all the multicast groups.

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The RP is, of course, 10.1.1.1.

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Notice that this, again,
is only for version 2.

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Our info source is the
bootstrap router 10.1.1.1.

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We've, of course, learned
this via bootstrap.

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We see the default priority is
0 because we didn't change it.

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And the current
hold time is 150.

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It's been up for 18
seconds, and it expires

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in 2 minutes and 7 seconds.

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If we do a show ip pim bsr, we
can get some more detail on BSR

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itself.

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Again, we see that this
is only PIM version 2.

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This system is the BSR.

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The BSR's address
is the 10.1.1.1.

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We can see, of
course, our uptime,

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the default priority of 0, the
default hash mask length of 0.

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And we also see that it's
learned the candidate

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RP of 10.1.1.1.

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It's being advertised
every 60 seconds.

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And the whole time is,
again, that 150 seconds

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that we saw previously.

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And just to wrap up, if we
do our show ip mroute again,

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we've added no
additional groups here.

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And if we look at our
igmp groups again,

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we've added no additional
groups here either

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because, again, BSR does not
require any additional groups

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in order for it to function.

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In this video, we
took a look at BSR,

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which is, again, the
industry standard

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version of Cisco's AutoRP.

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I only call it that because
Cisco AutoRP, of course,

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came out first in PIM version 1.

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And then the industry
came out with BSR

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starting with version 2.

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We can also see
that they function

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a bit the same in that
there's the candidate RPs,

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and then there's the device.

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AutoRP calls it
the mapping agent.

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And BSR calls it, well, the BSR
that collects this information

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and sends it out to
the other routers.

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Now, that's, of
course, where things

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start to get a little different,
where all of the other routers

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would learn all of
the candidate RPs.

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And they each make
their own decisions

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where in AutoRP
the mapping agent

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made that decision for us.

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Again, we will review
this in a little bit more

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detail when we have
a larger environment

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during our multicast
implementation skills.

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For now, we need to take a
look at this thing called

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Anycast RP.

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And that's exactly what we're
going to jump in and take

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a look at 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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