Nagios XI - The industry standard for IT infrastructure monitoring
Nagios XI is a system and network monitoring  application. It watches hosts  and services that you specify, alerting  you when things go bad and when  they get better. Some of its many  features include monitoring of network   services (SMTP, POP3, HTTP, NNTP, ICMP, etc.), monitoring of host   resources (processor load, disk usage, etc.), and contact notifications   when service or host problems occur and get resolved (via email, pager,   or user-defined method).
 With Nagios you can:  
- Monitor your entire IT infrastructure
 - Spot problems before they occur
 - Know immediately when problems arise
 - Share availability data with stakeholders
 - Detect security breaches
 - Plan and budget for IT upgrades
 - Reduce downtime and business losses
 
