Nagios, 2nd Edition

Appendix B. Rapidly Alternating States: Flapping

If the state of a host or service keeps on changing over and over, Nagios inundates the administrator with a flood of problem and recovery messages, which can not only be very irritating but also distract the administrator's attention from other, perhaps more urgent problems.

With a special mechanism, Nagios quickly recognizes alternating states and can inform the administrator of these selectively. The Nagios documentation refers to such alternating states as state flapping and to their detection as flap detection.

Whether these alternating states involve hosts or services has no influence on the detection mechanism itself. The differences are more to be found in the nature of host and service checks: ...