HostMonitor is a highly scalable network monitoring software suitable for small and enterprise-level networks
HostMonitor is a network-monitoring tool that allows you to keep a close eye on what is going on the network. Monitoring is done by performing periodic checks of the network resources that are to be watched. These checks, in the HostMonitor terminology, are called tests. It is the administrator’s responsibility to identify exactly what needs to be checked, and create a set of tests that will be doing the job.
PING, Trace, SMTP, POP3, Mail Relay, TCP, UDP, NTP, DNS, DHCP, RAS, UNC, RADIUS, Services, Process, CPU Usage, SNMP …
http://www.ks-soft.net/hostmon.eng/index.htm