When a host is configured with an IPv6 address using a static or other dynamic mechanism (like SLAAC or DHCPv6), the host will send an ICMPv6 NS message to the new IPv6 address before assigning the address to the interface. If the address that is being validated for DAD is the only IPv6 address available for the host, the NS message will be sent with an all-zero IPv6 address, as shown in the following screenshot:

As mentioned in the ND section, an NS message will be sent to the solicited node multicast address. If it gets a response from any node, the host will detect the presence of another host with the same address and so it will not assign this duplicate address. If it does not receive any NA from any host, it is safe to assign and use the IPv6 address.