This memo specifies an optional interim mechanism for IPv6 sites tocommunicate with each other over the IPv4 network without explicittunnel setup, and for them to communicate with native IPv6 domainsvia relay routers. Effectively it treats the wide area IPv4 networkas a unicast point-to-point link layer. The mechanism is intended asa start-up transition tool used during the period of co-existence ofIPv4 and IPv6. It is not intended as a permanent solution.The document defines a method for assigning an interim unique IPv6address prefix to any site that currently has at least one globallyunique IPv4 address, and specifies an encapsulation mechanism fortransmitting IPv6 packets using such a prefix over the global IPv4network.The motivation for this method is to allow isolated IPv6 domains orhosts, attached to an IPv4 network which has no native IPv6 support,to communicate with other such IPv6 domains or hosts with minimalmanual configuration, before they can obtain natuve IPv6connectivity. It incidentally provides an interim globally uniqueIPv6 address prefix to any site with at least one globally uniqueIPv4 address, even if combined with an IPv4 Network AddressTranslator (NAT).
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