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IPv6 multicast: [41] The low 32 bits an Ethernet address for IPv6 multicast traffic are the low 32 bits of the multicast IPv6 address used. [ 40 ] : §2.3.1 For example, IPv6 multicast traffic using the address ff02::d uses the MAC address 33-33-00-00-00-0D , and traffic to ff05::1:3 goes to the MAC address 33-33-00-01-00-03 .
The solicited-node multicast addresses are generated from the host's IPv6 unicast or anycast address, and each interface must have a solicited-node multicast address associated with it. A solicited-node address is created by taking the least-significant 24 bits of a unicast or anycast address and appending them to the prefix ff02::1:ff00:0 / 104 .
For IPv6 multicast addresses, the Ethernet MAC is derived by the four low-order octets OR'ed with the MAC 33:33:00:00:00:00, so for example the IPv6 address ff02:dead:beef::1:3 would map to the Ethernet MAC address 33:33:00:01:00:03. [7]
IPv6 addresses are assigned to organizations in much larger blocks as compared to IPv4 address assignments—the recommended allocation is a / 48 block which contains 2 80 addresses, being 2 48 or about 2.8 × 10 14 times larger than the entire IPv4 address space of 2 32 addresses and about 7.2 × 10 16 times larger than the / 8 blocks of IPv4 ...
With such an assignment it is possible to embed the unicast address prefix into the IPv6 multicast address format, while still providing a 32-bit block, the least significant bits of the address, or approximately 4.2 billion multicast group identifiers.
This results in the following well-known practical multicast addresses for SSDP: 239.255.255.250 (IPv4 site-local address) ff02::c (IPv6 link-local) ff05::c (IPv6 site-local) Additionally, applications may use the source-specific multicast addresses derived from the local IPv6 routing prefix, with group ID c (decimal 12).
To perform ICMPv6 Neighbor Discovery, multicast must be used. Any IPv6 multicast packet gets encapsulated in an IPv4 multicast packet with destination 239.192.x.y, where x and y are the penultimate and last bytes of the IPv6 multicast address respectively.
An IPv6 packet is the smallest message entity exchanged using Internet Protocol version 6 (IPv6). Packets consist of control information for addressing and routing and a payload of user data. The control information in IPv6 packets is subdivided into a mandatory fixed header and optional extension headers.