Cacti
A service which runs over SNMP (the Simple Network Management Protocol). It uses a poller to periodically pull data from hosts, which it then stores in a database backend using RRDTool. It is most often used to monitor system statistics, such as CPU usage, load, networking traffic, etc, which are then displayed in the form of graphs. Its very flexible, and because it uses SNMP, with the proper plugins it can be used to query both *nix and Windows boxes. To view our graphs go to https://cacti, or to log in for configuration and graph management go to https://qubit/cacti. For information on our specific configuration visit here.
Nagios
A service which uses a variety of methods to keep track of the state of machines. It can be used to monitor almost anything such as system availability, service status, warning about disk usage, etc on almost any host. It is highly extensible through the use of plugins, and can be used for both active and passive checks. Active checks being those in which the nagios server itself conducts a check (such as pinging a machine to determine uptime, or using snmp to check the status of something), and passive checks which involve writing information to a file which nagios looks at (these usually aren't conducted through the nagios service). It offers a wide variety of options for notification such as email and paging, and can be configured with multiple contacts and rules for what to do when a problem escalates (usually based on time, or number of failures). It also provides for systems and contacts to be grouped logically, and keeps track of the state over time, so that you can view the trends for individual services or systems. Our nagios page can be found at https://nagios, but you must be a member of the IT group to access it. For information on our specific configuration visit here.