Lumeta 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 Lumeta's database when it has been inactive for 7 days.
The criteria for a device to go "inactive" is 3x the shortest rescan interval of any collector in a single zone.
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 * 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.