If the external network is down, the app control function will no longer be available. But the local control for the sensor will not be affected and its connection with other smart devices will function normally. The sensor can still be triggered, and after being triggered, the sensor will execute corresponding function according to the previous setting in the app. For example, if the Aqara Hub has entered security mode before the connection is down, the Aqara Hub will play an alarm once the sensor is triggered.