A link-local address is useful only in the context of the local link network; its scope limits its relevance to only one link. A link-local address is an IPv6 unicast address that can be automatically configured on any interface by using the link-local prefix FE80::/10 (1111 1110 10) and the 64-bit interface identifier, as shown in Figure 6-20. Link-local addresses are used in the neighbor discovery protocol and the dynamic address assignment process. Dynamic address assignment is discussed in more detail in the next section.
Figure 6-20 IPv6 Link-Local Unicast Address Structure
1111 1110 10
A link-local unicast address connects devices on the same local network without requiring globally unique addresses.
Many routing protocols also use link-local addresses.
When communicating with a link-local address, the outgoing interface must be specified, because every interface is connected to FE80::/10.
An IPv6 router must not forward packets that have either link-local source or destination addresses to other links.
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