If this optional flag is enabled, use only Status-Server requests (if any) to determine that a target server is failed when there is no reply. If not enabled (the default) use no-reply to any type of request. This parameter uses NoreplyTimeout, MaxFailedRequests, MaxFailedGraceTime, FailureBackoffTime during failure detection.

If you enable this, ensure also KeepaliveTimeout is set to a sensible interval to balance between detecting failures early and loading the target server.