You can define a threshold value for specific interfaces to monitor their status. If an interface remains down beyond the defined threshold value, an alert will be generated.
For more information, refer to the feature walkthrough video available at: SonicWall Network Security Manager - How to Configure Alert Thresholds.
To configure interface settings
Click the Settings icon next to the Interfaces under the Device Management group.
Set the Interface state change alert threshold value.
You can set the value between 0 and 1440 minutes.