Nagios - Open Source Versatile Infrastructure Alerting Solution

Nagios is an open source product, which means most of the support comes from the community. Unless you purchase one of the paid products, such as Nagios XI, you can't really expect to see any level of meaningful or traditional enterprise level support. But there's also a distinct lack of account management for the open source product as well, so there isn't a path inside the company typically for customer support.

Nagios is well suited to monitoring devices such as network switches, printers, and especially servers, as well as if administrators or end users wish to receive alerts for downtime or other outages so they can be addressed. It is less appropriate for if auditing of services or logging of those services is desired, or if anything beyond up/down or specific application checks are needed in order to monitor a service.