Which prefix indicates that an address is a site-local address in IPv6?

The prefix that indicates a site-local address in IPv6 is FC00::/7. Site-local addresses are meant to be used within a single site or organization and are not routable on the global Internet. This makes them useful for local communication among devices in a private network. The FC00::/7 prefix specifies the range for these unique local addresses (ULAs), with the range extending from FC00:: to FDFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF:FFFF.

In contrast, the other prefixes listed serve different purposes. The FE80::/10 range is designated for link-local addresses, which are used for communication between nodes on the same local link and cannot be routed; these addresses typically begin with FE80 followed by 54 bits of zeros. The FF00::/8 range is reserved for multicast addresses, allowing packets to be sent to multiple interfaces. Lastly, the 2000::/3 range is for global unicast addresses that are routable on the Internet.

Understanding these distinctions helps in grasping how IPv6 addressing works, particularly the roles of different address types.