Adds the IPv6 address range to the relevant existing IPv6 address block. If there is no IPv6 address block existing, then ...

Adds the IPv6 address range to the relevant existing IPv6 address block. If there is no IPv6 address block existing, then the added IPv6 address range would be mapped under Unicast global addresses  and Unmapped address space and it would be mapped to the appropriate IPv6 address block only on  creation of the same.