Hi Iain.
Did you have remote access to NAS before NBN? Would that have been via ADSL with fixed ip address? What setups did you have to do at that time?
Regarding NBN:
dynamic ip address needs a Dynamic DNS (DDNS) to be setup in the AC1200. This allows you to find your network if the ip address changes. The AC1200 has 3 options. You register with whichever provider you choose.
How does the NAS appear on the local network? As an FTP server on some port number?
You may need to consider setting up a VPN so your remote computer can appear to be a device on the local network. AC1200 supports OpenVPN so you need OpenVPN client on your remote computer.
Port forwarding might be needed depending on NAS. OpenVPN on AC1200 might also activate the port forwarding for its own use.
Except, VPN may no longer be an option on AC1200, so don't upgrade AC1200 firmware if you still have VPN option.
And, port forwarding is an unknown. Some users have reported that TPG is blocking ports; TPG say to use ports between 30000-40000. You may need to use a port in this range for VPN.
