As far as the reason for its use, the reality of that answer is NO. IPv4 NAT is used to help relieve the global IP v4 address shortage. IPv6 has no address shortage problem. Some people believe it is used for the purpose of providing security, but that is
Generally, while the use of NAT with IPv6 is possible, I (and others) believe that its use should be discouraged. The article that I linked to talks to some of the reasons that NAT should not be used.
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