IPv6 Addressing
The Unspecified Address
The Unspecified AddressThe “unspecified” address is defined as 0.0.0.0.0.0.0.0 (::/128, or just ::). It can be used, for example, as a temporary source address in multicast traffic sent by an interface that has not yet acquired its own address. The unspecified address cannot be statically configured on the switch, or used as a destination address.
IPv6 Address DeprecationPreferred and Valid Address Lifetimes
Autoconfigured IPv6 global unicast addresses acquire their valid and preferred lifetime assignments from router advertisements. A valid lifetime is the time period during which an address is allowed to remain available and usable on an interface. A preferred lifetime is the length of time an address is intended for full use on an interface, and must be less than or equal to the address's valid lifetime.
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When the preferred lifetime expires, the address becomes deprecated, meaning that the address should no longer be used as a source address (except for existing exchanges that began before the timeout occurred), but can still be used as a destination. When the timeout arrives for the valid lifetime, the address becomes unusable.