Nagios Is The Industry Standard In IT Infrastructure Monitoring
Achieve instant awareness of IT infrastructure problems, so downtime doesn't adversely affect your business.
Nagios offers complete monitoring and alerting for servers, switches, applications, and services.
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