Brian, your thought was correct.

I just tested this using 4 routers in a string:  R1 - R2 - R3 - R4

R1 is the mrm sender, R2 is the mrm manager, R3 is the RP/mapping
agent, R4 is the mrm receiver.

With the "ip pim spt-threshold infinity" option set, R4 only showed
the (*,G) mroute entries, but R1, R2, and R3 all showed (S,G) mroute
entries with R1 as sender.

But with bidirectional PIM, all 4 routers only show (*,G) mroute entries.

Without bidirectional or spt-threshold infinity, all 4 routers show
(S,G) mroute entries.

On Sun, Jul 26, 2009 at 2:44 PM, Bryan Bartik<[email protected]> wrote:
> Good point Jason. I think the task is hinting at using Bi-directional PIM.
> Disabling the SPT switchover would force all the receivers downstream of the
> RP to stay on the RP tree (*, G). My only concern is if there is host
> between the RP and the Source. With SPT threshold set to zero, would the
> router between the source and RP still pull from the SPT?...haven't tested
> it, but might be something to look into.
>
> On Sun, Jul 26, 2009 at 12:10 PM, jmangawang <[email protected]> wrote:
>>
>> Ok, I'd just like a little clarification on another solution after
>> just having gone through this myself.
>>
>> My solution was to configure "ip pim spt-threshold infinity" on all
>> participating routers.  When I did a "show ip mroute" while the MRM
>> test was running (from next task), I did not see any (S,G) entries,
>> only (*,G) entries except on the sender's table.  On a whim, I removed
>> the "ip pim spt-threshold infinity" command from all routers, then
>> enabled "ip pim bidir-enable" on each, configured the RP to send out
>> bidir, and re-ran MRM.  My "show ip mroute" tables looked identical
>> with the exception that every entry had "bidir" in it.
>>
>> And finally, I removed all instances of "bidir" and "spt-threshold"
>> and just ran everything normal, and the mroute tables DID show (S,G)
>> entries, like I'd expect them too.
>>
>> So, would the "ip pim spt-threshold infinity" command been an
>> acceptable solution for this?
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