All things related to multicast

[Jeff Fitzwater <>]

This may be slightly off topic but you guys must know the answer to this.


I believe I understand how IGMP SNOOPING works and everything I have 
read and tested tells me that the MULTICAST DATA will always be passed 
toward the QUERIER (This should be the router in most cases).    Is this 
correct and works as designed so it can handle non-IGMP capable routers 
that do not generate JOINS (REPORTS).

In our case we have the multicast SRC and CLIENT downstream of the 
router but the router is the QUERIER, so therefor the downstream switch 
hears the report from the client and adds it to his table.  Now when the 
multicast data flows it not only goes out to the client but also out 
toward the QUERIER (router).

I would think this would just suck up unnecessary BW on the router link.


Q.   Does the data always get sent to the QUERIER even if there are no 
listeners at the router ???



I hope I described it OK.


Thanks for any response.



Jeff Fitzwater
OIT Network Systems
Princeton University