[c-nsp] MSDP and my limited knowledge question

[Phil Mayers]

On 09/04/2012 09:12 AM, Adam Vitkovsky wrote:
> As Paul said IGMP register messages are supposed to be handled by the router
> elected as designated querier for the local subnet
> Though AFAIK IGMP register process is only used by the m-cast receivers not
> the sources

For clarity, because I think you typo-ed a couple of things there:

PIM registers are sent for multicast *sources*. They're sent by the PIM 
designated forwarder towards the RP and flooded down the (*,g) tree so 
that (s,g) joins can be triggered. They are re-sent periodically to 
refresh state on the RP.

IGMP joins are sent by multicast *receivers*. They trigger (*,g) joins 
[or (s,g) joins for IGMPv3 SSM] towards the RP. When a new source 
appears on the (*,g) tree, the routers are triggered to do an (s,g) join.

MSDP essentially "echos" PIM register state between PIM RPs, allowing 
separate PIM networks to be connected without (*,g) flooding on the 
interconnect link, which wouldn't scale well.

The OPs problem is that he's trying to source multicast traffic from an 
IP on his Linux box that isn't a "connected" route on the c4900. Thus, 
the c4900 isn't the PIM DF, so doesn't send the PIM register or MSDP 
advertisments. That doesn't (can't) work, I believe.

AFAIK there's no "PIM DF proxy" IOS feature, though I can see situations 
in which it would be useful.