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I had a look at the specs of your modem ( PYTHON DSL-2888A Dual Band Wireless AC1600 Gigabit ADSL2+/VDSL2 Modem ) on the Dlink page and can see that this is NBN ready.
You may use it, however, the homephone feature will not work since the configuration of the VoIP phone is embedded in our modem's firmware.
So apart from the phone, internet should work fine.
The reason I am asking this question is that my current modem/router broke down and I have to buy a new one.
I have ADSL2 at the moment but will get NBN between July to Sept 2018. I was thinking of buying D-Link PYTHON DSL-2888A AC1600 Gigabit ADSL2+/VDSL2 Modem Router. This modem/router has VDSL and ADSL. I assume it will work now with ADSL and later with NBN.
Yes, that should work. In case you need assistance in the future to setup this modem. Do not hesitate to let us know. We are here to help.
Let me know if there is anything we can assist you with.