During the configuration process of your D-Link range extender, you have to make sure that you know the Wi-fi password of your router with which you have connected your range extender. The configuration process of the dlinkap.local interface requires an active internet connection, without an active Wi-fi you won't be able to configure your range extender. You can also keep the same Wi-fi password for both the Wi-fi bands of your extended network by selecting the "Use the same password for both the networks" option while personalizing your range extender's network.
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