Over a period of time a small network grows into a larger network. Tracking hosts for availability is constant challenge for an admin on a large network.
For my home network I decided to implement a network management system because the number of hosts on my network had grown to a larger number than I could keep track of. I wanted something simple that would give me the functionality of up or down and have the ability to save notes on a host and get basic trending data regarding availability.
I installed 3 Virtual machines and installed Cacti, Nagios and OpenNMS within them. Out of the 3 packages I evaluated OpenNMS was surprisingly the easiest to configure and work with and provided the most functionality.
With a basic configuration OpenNMS will seek out all of the hosts in the network range you specify and list all the services that are running on those hosts. I honestly wish I had installed OpenNMS first as I spent a lot of time editing the overly complicated Nagios configuration file to even get one host monitored. In the time that it took me to get Nagios working for one host OpenNMS would have been completely setup with all the hosts in the configuration.