The first thing that needs to be done in order to use passive checks for your Nagios setup is to make sure that you have the following options in your main Nagios configuration file:

accept_passive_service_checks=1
accept_passive_host_checks=1

It would also be good to enable the logging of incoming passive checks — this makes determining the problem of not processing a passive check much easier. The following directive allows it:

log_passive_checks=1

Setting up hosts or services for passive checking requires an object to be defined and set up so as not to perform active checks. The object needs to have the passive_checks_enabled option set to 1 for Nagios to accept passive check results over the command pipe.

The following is an example of the required configuration for a host that accepts passive checks and has active checks disabled:

define host {
use generic-host
host_name linuxbox01
address 10.0.2.1
active_checks_enabled 0
passive_checks_enabled 1
}

Configuring...