A device may drop packets or fail to respond to a poll for many reasons. Should the device fail to respond, the device status is changed from Up to Warning. On the Polling Settings view, you can specify the Node Warning Level, which is the length of time a device is allowed to remain in the Warning status before it is marked as Down. During the interval specified, the service performs "fast polling" (ICMP) to continually check the node status.
You may see events or receive alerts for down nodes that are not actually down. This can be caused by intermittent packet loss on the network. Set the Node Warning Interval to a higher value to avoid these false notifications. For more information about packet loss reporting, see Manage packet loss reporting
In the Calculations and Thresholds group, set the Node Warning Level to an appropriate interval, in seconds.
The default Node Warning Level interval is 120 seconds.