From: Bob Sinclair (bob@bobsinclair.net)
Date: Sat Mar 29 2008 - 22:02:40 ART
Daniel Valle wrote:
> R2 is the MA and is also the RP for the mcast groups
>
> R1 and R3 are Spokes
>
> R3 f0/0 is set to ip igmp join-group 224.3.3.3
>
> If I set the FR network as OSPF network
> point-to-multipoint the R1 ( spoke) pings 224.3.3.3 just fine, if I set the
> network to the default ( non broadcast), it does not work.
>
>
>
Daniel,
I assume you are running NBMA-mode on the hub. As I understand your
scenario: with the non--broadcast OSPF network type you get a few pings
then nothing.
Here is what could explain this:
You get a few packets on the shared tree and R3 responds. R3 sends a
source-tree join, gets another packet on the shared tree, and sends a
shared tree prune. R2, the hub, ignores the source tree join because it
does not have its address as the upstream neighbor. The source-tree
join has R3's address. With the non-broadcast OSPF network type the
routers model the underlying Layer 2 as multi-access.
In sparse mode, R3 is not supposed to prune off the shared tree until it
gets packets on the source tree. The failure of the source tree is
hidden by the fact that on R3 the shared tree RPF and the source tree
RPF are the same interface.
Try repeating the experiment while sending debug ip pim to the buffer.
I would expect you to see the ping fail after the shared tree prune goes
out to R2. You can tell the shared tree prune: it will be sent to R2
(actually multicast to 224.0.0.13, but addressed in the data portion)
and it will have the RPT bit set.
HTH,
Bob Sinclair
Netmasterclass.net
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