When does a device become inactive?

Asset Manager designates a device as inactive when the Command Center doesn't receive a response from it for three consecutive indexing cycles of the shortest length. In this, shortest length is the shortest rescan interval of any collector in a zone. The response pertains to active responses only, not to passive (e.g., OSPF, BGP protocols) ones. An inactive device is dropped from zone reports and Asset Manager's database when it has been inactive for seven days. 

Devices created by any external source (Meraki, Qualys, Tenable, Infoblox) will go inactive if it is not active after two days and will age out after seven days.

For example, in a zone with Collector A and Collector B, where Collector A has a rescan interval of 5 and Collector B has a rescan interval of 20, the device will be flagged as inactive if the system does not receive a response in 15 minutes (3 x 5). If that inactivity persists for 7 days, that device will be dropped from new reports generated. 

Passive discovery (broadcast, OSPF, BGP) does not depend on collector rescan interval because passive discovery never sends out packets. The rescan interval can be set to anything and passive discovery types will not be not impacted.

The thresholds on when devices become inactive, device attributes removed, or device removed can be changed with database commands and updating the expireDataMins or maxDeviceAge fields in the system.config table.

For example the sql command insert into system.config (key,value) values('maxDeviceAge',20160); will change the threshold of device deletion from the default of 7 days to 14 days.