In PIM-SM operations, the first router connected to the multicast source sends the Register
message to which device?

A.
Designated Router (DR)

B.
Multicast source

C.
Multicast receiver

D.
RP mapping agent

E.
RP

Explanation:
A multicast data sender just starts sending data destined for a multicast group. The sender’s local
router (DR) takes those data packets, unicast-encapsulates them, and sends them directly to the
RP. The RP receives these encapsulated data packets, decapsulates them, and forwards them
onto the shared tree. The packets then follow the (*,G) multicast tree state in the routers on the RP
Tree, being replicated wherever the RP Tree branches, and eventually reaching all the receivers
for that multicast group. The process of encapsulating data packets to the RP is called registering,
and the encapsulation packets are known as PIM Register packets.