Which statement about IPv6 link-local addresses is true?

Question:
Which statement about IPv6 link-local addresses is true?

• They must be configured on all IPv6 interface
• They must be globally unique
• They must be manually configured
• They are advertised globally on the network

Explanation: Link-local addresses refer only to a particular physical link and are used for addressing on a single link for purposes such as automatic address configuration and neighbor discovery protocol. Link-local addresses can be used to reach the neighboring nodes attached to the same link. The nodes do not need a globally unique address to communicate. Routers will not forward datagram using link-local addresses. All IPv6 enabled interfaces have a link-local unicast address.

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are not necessarily bound to the MAC address (configured in a EUI-64 format). Link-local addresses can also be manually configured in the FE80::/10 format using the “ipv6 address link-local” command.

Reference: http://www.cisco.com/c/en/us/support/docs/ip/ip-version-6-ipv6/113328-ipv6-lla.html

In summary, if you do not configure a link-local on an IPv6 enabled interface, it will automatically use the FE80::/10 and the interface identifier in the modified EUI-64 format to form a link-local address.

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