A method of Internet Protocol version 6, IPv6, duplicate address detection, DAD, proxy, comprising: Obtaining (101, 201) a DAD-neighbor solicitation, DAD-NS, message, the DAD-NS message comprising address information sent by a subscriber and access location information corresponding to the address information, wherein the address information comprises at least an IP address to be detected and a link layer address; Comparing (102, 202) the obtained DAD-NS message with locally stored DAD information, and adding the DAD-NS message to the locally stored DAD information when it is determined, according to a comparison result, that the IP address to be detected is not duplicate; when it cannot be determined, according to a comparison result, whether the IP address to be detected is duplicate or not, initiating, according to the address information comprised in the locally stored DAD information after comparison, an unreachability detection to the IP address to be detected to determine whether the IP address to be detected is duplicate,; wherein the DAD information comprises address information and access location information of at least one subscriber; characterized in that, the determining, according to the comparison result, that the IP address to be detected is not duplicate comprises: if the comparison result indicates that the link layer address and the access location information comprised in the obtained DAD-NS message are the same as those comprised in the DAD information, but the IP address to be detected is different, or if the comparison result indicates that the access location information comprised in the obtained DAD-NS message is the same as that comprised in the DAD information, but the link layer address and the IP address to be detected are different, or if the comparison result indicates that the link layer address comprised in the obtained DAD-NS message is the same as that comprised in the DAD information, but the access location information and the IP address to be detected is different, or if the comparison result indicates that the access location information, the link layer address and the IP address to be detected that are comprised in the obtained DAD-NS message are different from those comprised in the DAD information; determining that the IP address to be detected is not duplicate. Obtaining (101, 201) a DAD-neighbor solicitation, DAD-NS, message, the DAD-NS message comprising address information sent by a subscriber and access location information corresponding to the address information, wherein the address information comprises at least an IP address to be detected and a link layer address; Comparing (102, 202) the obtained DAD-NS message with locally stored DAD information, and adding the DAD-NS message to the locally stored DAD information when it is determined, according to a comparison result, that the IP address to be detected is not duplicate; when it cannot be determined, according to a comparison result, whether the IP address to be detected is duplicate or not, initiating, according to the address information comprised in the locally stored DAD information after comparison, an unreachability detection to the IP address to be detected to determine whether the IP address to be detected is duplicate,; wherein the DAD information comprises address information and access location information of at least one subscriber; characterized in that, the determining, according to the comparison result, that the IP address to be detected is not duplicate comprises: if the comparison result indicates that the link layer address and the access location information comprised in the obtained DAD-NS message are the same as those comprised in the DAD information, but the IP address to be detected is different, or if the comparison result indicates that the access location information comprised in the obtained DAD-NS message is the same as that comprised in the DAD information, but the link layer address and the IP address to be detected are different, or if the comparison result indicates that the link layer address comprised in the obtained DAD-NS message is the same as that comprised in the DAD information, but the access location information and the IP address to be detected is different, or if the comparison result indicates that the access location information, the link layer address and the IP address to be detected that are comprised in the obtained DAD-NS message are different from those comprised in the DAD information; determining that the IP address to be detected is not duplicate. if the comparison result indicates that the link layer address and the access location information comprised in the obtained DAD-NS message are the same as those comprised in the DAD information, but the IP address to be detected is different, or if the comparison result indicates that the access location information comprised in the obtained DAD-NS message is the same as that comprised in the DAD information, but the link layer address and the IP address to be detected are different, or if the comparison result indicates that the link layer address comprised in the obtained DAD-NS message is the same as that comprised in the DAD information, but the access location information and the IP address to be detected is different, or if the comparison result indicates that the access location information, the link layer address and the IP address to be detected that are comprised in the obtained DAD-NS message are different from those comprised in the DAD information; determining that the IP address to be detected is not duplicate.