What is the IPv6 address prefix for a link-local unicast address?

The IPv6 address prefix for a link-local unicast address is FE80. Link-local addresses are used for communication between nodes on the same local link and are not routable beyond that link. The FE80::/10 prefix specifically designates these addresses.

When a device generates a link-local address, it typically uses the FE80 prefix followed by a 54-bit zero field and a 64-bit interface identifier. This allows devices to communicate without the need for a router, making it essential for network discovery and address autoconfiguration processes.

The other choices represent different types of IPv6 addresses or reserved ranges: FC00 is used for unique local addresses, 2001 is designated for global unicast addresses, and FFFF is not a valid prefix in the context of standard IPv6 addressing. Understanding these prefixes and their applications is crucial for distinguishing between the various types of IPv6 communication methods.