How to resolve unpingable host down status in Nagios

After installing nagios, you may face some issues

Some hosts are not able to be ping due to firewall. By default, Nagios use the check_host_alive by default at /etc/nagios/objects/template.cfg. check_host_alive uses ping to check whether the host is alive. So your nagios web admin will see a host down status.

To use another commands to replace the check_host_alive with check_http which is more useful as a "check-alive-status", change it at the /etc/nagios/objects/hosts.cfg file. This will override the default at /etc/nagios/objects/templates.cfg

We assume that check_http is already define in the /etc/nagios/objects/command.cfg

define host{
use windows-server
host_name xxxx
alias xxxx web server
check_command check_http
address xxx.com.sg
contact_groups admin
}