Question: Since I am using the 255.255.255.0 subnet mask and this address (10.0.1.54) is in the range within my normal network, am I going to run into problems?
When I look at the config of the cameras connected to the NVR using the direct connection (i.e. mouse and monitor) Menu->Cameras I see that the addresses showing for the 8 PoE cameras, using Plug & Play, have been assigned 10.0.1.2 through to 10.0.1.9. I assume that this means that the NVR is assigning these addresses based on the Internal NIC IPv4 address 10.0.1.54. However I have already used most of those addresses within my normal network! Will this cause issues?
Yes, having the the PoE interface IP address in the same range as the LAN address will definitely cause problems. You have already seen that there will potentially be IP address conflicts with multiple devices on your LAN which are assigned that same addresses from your router DHCP IP address pool.
But if you haven't seen any evidence of that, I could speculate that it may be due to the internal routing between PoE ports interface and the LAN interface being broken in your NVR.
Somehow you need to get the PoE interface address set to a range that's not on your LAN, ideally back to it's original default.
I wonder if the configuration complaint is anything to do with it checking for duplicates of the camera addresses? Hard to know.
There are various things to try, assuming you know how to set your PC to a fixed, static IP address.
Unplug the NVR LAN interface, and see if you still get an error when trying to set the PoE interface IP address via the HDMI connection. That way, it will not see any potentially clashing devices on the LAN.
Via the web GUI, change the NVR LAN interface to an address not on your LAN, say 192.168.1.100
Change your PC to say 192.168.1.10
Unplug the NVR LAN connection.
Via the HDMI connection, try to change the PoE interface IP address to 192.168.254.1
If that works, plug the NVR LAN connection back in, restart the browser and connect to
http://192.168.1.100, change the NVR LAN address back to your original 10.0.1.154, and your PC address back to its original settings.
If all else fails - there is always the 'Reset all parameters to default settings' in the Maintenance menu - but that may have other side effects depending on what configuration settings the running state of the NVR depends upon.