I'm in the process of setting up Nagios monitoring software for our servers. The other day, we lost connectivity to our remote servers, and notifications were duly sent out. The problems were acknowledged, and acknowledgment notifications were sent out as expected. However, once we regained connectivity to the hosts, the "Host UP" notifications were not sent. According to the Nagios logs, Nagios didn't even try to send the recovery notifications.
When connectivity was lost to the hosts before, and the problems were not acknowledged, the "Host UP" notifications were sent upon recovery. So it seems that the act of acknowledging a host problem prevents the recovery message being sent.
All hosts are configured to send notifications when "down, unreachable and recovery".
I'm running Nagios version 3.3.1.
Any help would be greatly appreciated!