Sample configuration code to check host availability (using ping) with Nagios.

Nagios

# Define our host
define host{
	use         linux-server
	host_name   someserver.local
	alias       someserver.local
	address     192.168.1.1
	}

# Define ping service parameters warning at 100ms response time and 20% packet loss
# and failure at 500ms response time and 60% packet loss
define service{
	use                             generic-service
	host_name                       infmgt.sme.loc
	service_description             ping
	check_command                   check_ping!100.0,20%!500.0,60%
	}