I wrote down some notes about configuring Nagios to check the health status of a few VMware vSphere ESXi 5.1.0 servers. First of all, install the required packages on the Nagios server:

NagVis (http://www.nagvis.org/) is a visualization addon for Nagios/Icinga that permits to visualize the monitored information as objects placed on maps.  I decided to use mk-livestatus (see: http://mathias-kettner.com) as backend because it is reported to offer better performances than ndo.