Multicast addresses in IPv6 are similar to multicast addresses in IPv4. They are used to communicate with dynamic groupings of hosts, for example all routers on the link (one-to-many distribution).
Here is a graphical representation of the IPv6 multicast packet:
IPv6 multicast addresses start with FF00::/8. After the first 8 bits there are 4 bits which represent the flag fields that indicate the nature of specific multicast addresses. Next 4 bits indicate the scope of the IPv6 network for which the multicast traffic is intended. Routers use the scope field to determine whether multicast traffic can be forwarded. The remaining 112 bits of the address make up the multicast Group ID.
Some of the possible scope values are:
1 – interface-local
2 – link-local
4 – admin-local
5 – site-local
8 – organization-local
E – global
For example, the addresses that begin with FF02::/16 are multicast addresses intended to stay on the local link.
The following table lists of some of the most common link local multicast addresses:
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