hi TechnoCat
Maybe you can try
login web admin page> open Network & Virtual Switch>Click Add > Advanced Mode
In the interface selection screen, check the Thunderbolt port you want to use (e.g., thunderbolt0 or thunderbolt1).
- Choose “Use static IP address”.
- Enter your desired IP address (e.g., 192.168.100.1) and subnet mask (e.g., 255.255.255.0).
- Complete the wizard and apply the configuration.
Seems if this can help assign static ip on nas T