D-Link DSL-2790U User Manual page 49

Configuration
This window allows you to set up a LAN interface. When you are
finished, click the Apply / Save button.
To access the IPv6 LAN Auto Configuration window, click the
IPv6 AutoConfig button in the LAN directory.
This window allows you to set up IPv6 LAN Auto Configuration.
When you are finished, click the Apply / Save button.