behind RED in remote and local network?


I want to use my NAS behind a RED15w from both my local LAN and also from remote LAN.

Remote LAN:
Local LAN:

The NAS should be available to both networks for storage and as a media-server.

I tried transparent split and I could set a dual-IP for a test-device, so it was pingable from remote LAN with and also from local, but for some reason the connection wasn´t stable.

Any idea, why the connection was not stable? or is it because of the dual-IP setting?

Is there a more practicable way to reach my goal?