Which of the following ranges is reserved for IPv6 SSM multicast addresses?

The Internet Assigned Numbers Authority (IANA) has reserved the IPv6 multicast address prefix FF3x::/32 for Source-Specific Multicast (SSM), as specified in RFC 4607. Within this range, a common and standardized method for creating SSM group addresses is the unicast-prefix-based format defined in RFC 3306. This format embeds a 64-bit unicast network prefix into the multicast address, leaving the final 32 bits for a unique Group ID. This results in a practical group prefix of /96 (128 bits total - 32 bits for Group ID = 96 bits for the prefix). Therefore, FF3X::/96 represents the specific range reserved for SSM group identifiers under this widely used mechanism.

A. FF1X::/16: This range is reserved for transient or dynamically assigned multicast addresses, not for well-known services like SSM.

B. FF3X::/16: This prefix is too broad. While it correctly identifies the prefix for permanent, prefix-based multicast addresses, the IANA allocation for SSM is the more specific FF3x::/32 range.

D. FF7X::/16: This range was part of an earlier, experimental proposal for source-specific multicast that has since been deprecated by RFC 7371 in favor of the unicast-prefix-based approach in the FF3x::/32 range.

1. Internet Engineering Task Force (IETF) RFC 4607, "Source-Specific Multicast for IP", H. Holbrook, B. Cain, August 2006.

Section 3, Page 4: "The IANA has allocated the IPv6 multicast address prefix FF3x::/32 for SSM." This establishes the foundational range for IPv6 SSM.

2. Internet Engineering Task Force (IETF) RFC 3306, "Unicast-Prefix-based IPv6 Multicast Addresses", B. Haberman, D. Thaler, August 2002.

Section 3, Page 3: This document defines the format for these addresses. The structure is | 8 | 4 | 4 | 8 | 8 | 64 | 32 | bits, corresponding to | FF | flgs | scop | res | plen | network prefix | group ID |. The 32-bit Group ID at the end leads to the /96 prefix for the group portion.

3. Nokia 7750 SR OS Multicast Routing Protocols Guide, Release 21.10.R1, "PIM".

Section: Source-Specific Multicast (SSM): "For IPv6, the IANA has reserved the FF3x::/32 address range for SSM. This allows for unicast-prefix-based allocation of SSM addresses, which helps to ensure the global uniqueness of the (S,G) channel." This confirms the vendor's adherence to the IETF standard.