Which of the following about PIM messages for IPv6 multicast routing is FALSE?

According to RFC 7761, which defines PIM-SM, PIMv6 messages that are sent hop-by-hop, such as Hello and Join/Prune messages, are destined for the link-local All-PIM-Routers multicast address (FF02::D). The standard explicitly requires that the source address for these link-local scope messages MUST be the link-local IPv6 address of the interface on which the message is transmitted, not its global unicast address. Using a global unicast address as the source for these specific messages is incorrect and violates the protocol specification.

A: This is true. PIM Hello and Join/Prune messages are sent to the reserved link-local scope multicast address FF02::D to reach all PIM routers on a given link.

B: This is true. Register messages are unicast packets sent from the First-Hop Router (FHR) to the Rendezvous Point (RP) to register a new multicast source.

D: This is true. Since Register messages are unicast packets destined for the RP, they must use a globally routable source address, which is typically the global unicast address of the FHR's outgoing interface.

1. RFC 7761: Protocol Independent Multicast - Sparse Mode (PIM-SM)

Section 4.3.1, "Hello Message Format": "IPv6 Source Address: The link-local IPv6 address of the interface on which the Hello message is sent." (This directly contradicts option C, making it the false statement).

Section 4.3.2, "Join/Prune Message Format": "IPv6 Source Address: The link-local IPv6 address of the interface on which the Join/Prune message is sent." (This further confirms option C is false).

Section 4.1, "PIM Message Transport": "PIM messages that are sent hop by hop, such as Hello and Join/Prune messages, are sent with an IPv6 Hop Limit of 1 to the ALLPIMROUTERS link-local multicast address (FF02::D)." (This confirms option A is true).

Section 4.4.1, "Source Registration": "The Register message is sent as a unicast IPv6 packet to the RP's address." (This confirms option B is true).

Section 4.3.3, "Register Message Format": "IPv6 Source Address: A unicast IPv6 address of the sending router." (This confirms option D is true).

2. Nokia 7750 SR OS Services Configuration Guide, Release 21.10.R1

Chapter: Multicast routing protocols, Section: PIM: "For IPv6, PIM messages are sent using the link-local address of the outbound interface as the source address. The destination address is FF02::D, All PIM Routers multicast address." (This aligns with RFC 7761 and confirms that link-local, not global unicast, addresses are used as the source for Hello and Join/Prune messages).