Nearly IPv6 Only Dual Stack Hosts

Once all of a dual stack IPv4 and IPv6 host's applications support IPv6, IPv4 connectivity becomes unnecessary. However, ceasing to provide a dual stack host with an IPv4 address via a DHCPv4 server can cause the host to continue to make periodic and unsatisfied DHCPv4 requests, imposing unnecessary broadcast traffic on an attached link. In this situation, it would be useful to continue to provide a host with an IPv4 address via DHCPv4, yet prevent it from using the IPv4 address for any connectivity outside of the host itself. This memo describes a DHCPv4 method to achieve this.