When neigbour solicitation and router solicitation are used to get the IPv6 address, then what is the role of 0:0:0:0:0:0:0:0/128? I am learning computer networks, but getting confused each time I proceed my analysis. Kindly help. Thanks in advance!

That is the IPv6 unspecified address, and you use it when you do not know an address or have an address. The IPv6 unspecified address (`::/128`) is explained in _RFC 4291, IP Version 6 Addressing Architecture, Section 2.5.2. The Unspecified Address_:

> 2.5.2. The Unspecified Address
>
> The address 0:0:0:0:0:0:0:0 is called the unspecified address. It must never be assigned to any node. It indicates the absence of an address. One example of its use is in the Source Address field of any IPv6 packets sent by an initializing host before it has learned its own address.
>
> The unspecified address must not be used as the destination address of IPv6 packets or in IPv6 Routing headers. An IPv6 packet with a source address of unspecified must never be forwarded by an IPv6 router.