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To simplify host renumbering, IPv6 requires IPv6 hosts to be
able to support multiple IPv6 addresses per interface. This is
similar in concept to the Cisco interface command "secondary IP
address," which allows an interface to use two IP addresses. The
IPv6 mechanism of multiple addresses per interface goes further
however. IPv6 allows the ability to identify an IPv6 address
assigned to an interface as either "valid," "deprecated," or
"invalid." A host can use a valid address both for the existing
communications and for establishing new communications. In contrast,
the host could use a deprecated address only for the existing
communications, but is not allowed to use such an address for new
communications. Finally, if a host has an address that is invalid,
that address cannot be used for any of the new or existing
communications. In the process of renumbering, a host's current IPv6
address would become deprecated, and the host would acquire (through
one of the IPv6 address autoconfiguration mechanisms) a new (valid)
address. As a result, all the new communications would use the new
address. |
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