From: gladston@br.ibm.com
Date: Thu Dec 16 2004 - 14:21:33 GMT-3
You should expect an answer from R2, when pinging from any other router.
In Sparse-mode, when you enter the command 'ip igmp join-group ..." R2 will join the Shared-Tree. You should see output of "show ip mroute" (*,G) on the three from RP down to R2.
To help you interpret the results, Willianson is a good source. Doyle v2 also covers Multicast.
For Sparse-dense-mode, everything is the same as sparse-mode if you have a RP for the multicast group.
If there is no RP for the multicast group, the behavior of Sparse-dense-mode is dense-mode. When the command "ip igmp join-group" is configured on R2 before some other router ping, there is no source, so the router can not set a (S,G). As soon as one of the other routers ping R2, this router will be the source for the group, and you should check the (S,G) on all routers down the three, from the source (one of the routers) to the destination (R2).
Problem that might arise:
RPF check for RP and Source
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