Explanation
The command ip nhrp map multicast dynamic should be only used on Hub router, not spoke. If we are running dynamic routing protocols based on multicast (like RIP, OSPF, EIGRP ...) we have to add the command ip nhrp map multicast dynamic in Hub to replicate all multicast traffic to all dynamic entries in the NHRP table (multicast will be proceeded as unicast traffic) - The tunnel source FastEthernet0/0 is equivalent to tunnel source 172.17.0.2, which is the NBMA address of Spoke A.