Monitoring Windows Reboots through SNMP traps with Nagios

One fine day it happened: Nagios missed to alarm us for a server going down. One of the Windows servers (what else) rebooted due to a unknown cause (what else). Only it happened so darn fast that it fell exactly in between the five minute intervals when Nagios sends its 'ping' checks to verify the system is up. It is a quite rare case, only one single Nagios 'ping' check failed. With 'ping' being set to re-test after one minute for 2 more times (to avoid sending false alerts), it was recording one fail but did not send the necessary notification.

Clearly, passive 'ping' monitoring is not perfect, so a better way to monitor these pesky 'secret' Windows reboots is to make them send SNMP traps. Now, at least we will know for sure when they come back up. ;-) The linked tutorial has been developed and verified unter Nagios 3.0.2 running on SuSE Linux Enterprise Server 11, receiving traps from Windows 2003/2008 Servers and Windows XP clients.