You can use WAN as IPv6 from the version of NVR below. (As of July 2020)
The setting is available by selecting IPv6 in ‘Settings-Network-WAN’.
* IPv6 can be used only in the WAN used for remote access and cannot be set in VIN (Video IN) to register the camera.

DR-13xxP / 6.1.0 or higher
DR-22xxP / 6.1.0 or higher
DR-23xxP / 6.1.0 or higher
DR-24xxP / 6.1.0 or higher
DR-42xxP / 6.1.0 or higher
DR-43xxP(S) / 6.1.0 or higher
DR-62xxP(S) / 6.1.0 or higher
DR-63xxP(S)-(S)(A) / 6.1.0 or higher
DR-84xx(D) / 6.1.0 or higher
DR-8364D / 6.1.0 or higher