[c-nsp] PIM SSM behavior when receiving IGMPv3 *,G joins

[John Neiberger]

On Fri, Apr 29, 2011 at 11:43 AM, John Neiberger <jneiberger at gmail.com> wrote:
> Let's say we have an SSM range of 232/8 in our network. There is a
> multicast receiver connected to a 4948, which has a routed link to
> another 4948 running PIM and a routed link to a Cisco router, also
> running PIM. The multicast receiver sends the equivalent of a *,G
> join, which in SSM is a membership report set to EXCLUDE mode with a
> null source list. It's basically telling the switch, "I want to join
> x.x.x.x group and I don't care what the source is." What is the 4948
> supposed to do with that? I've read one page (non-Cisco site) that
> seemed to indicate that those sorts of joins would be dropped. Is that
> actually the case, or should the 4948 send a PIM message to its
> neighbors letting them know to forward that group to it if they have
> it available?
>
> I'm just not sure how this valid IGMPv3 join is supposed to be handled
> in an SSM environment. The situation has come up and I have no idea
> what the expected behavior is.
>
> Thanks!
> John
>

To answer my own question, I think, I just found this in RFC 4607:

   A router that receives such a
   non-source-specific request for data in the SSM range MUST NOT use
   the request to establish forwarding state and MUST NOT propagate the
   request to other neighboring routers.