tanyero wrote:

But trying to avoid having three devices (NBN Network Connection Device -> third-party router -> RBR850 in AP mode). When really I should be able to go (NBN network connection device -> RBR850 in router mode). Which does work for internet, IoT, etc.

Which basically what I am doing.

tanyero wrote:

Essentially the RBR is the router/gateway to access the internet, also providing wifi (mesh) for local LAN, also DHCP service, which is working for all other services except the NAS! I'm stumped!

This should certainly be working, at least on the NIC port that is configured for DHCP.

If you have other devices on the network where you have set up static addresses (in the device, not reserved in the Orbi), then you might also want to look for an IP address conflict.

Alternatively, turn off everything but the NAS and one PC, and see if that makes any difference.

One other thing you could try is to set up a direct connect from one of the LAN ports to a PC. Bypassing the router, and setting up static addressing on both the NAS and the PC (using a different subnet from the Orbi LAN).

Then you could connect the PC to the NAS using the direct ethernet connection, and connect the NAS to the Orbi. Don't connect the PC to the Orbi (for instance with WiFi) initially/

That would allow you to do more tests - for example,

looking at the NAS logs
pinging other devices on the Orbi network using ssh,
running tracert to make sure the connection topology is what you expect.

Forum Discussion

How many RBS850 satellites will a RBR850 router support