What Groundwork has done is to package Nagios, a free, open source, network management system along with a suite of supporting tools in a VMware appliance to create a product that is not only powerful but also basically turnkey.
Let me digress and note that no one produces virtual appliances based on Windows because of licensing issues, which is a shame because it would make evaluation of many Windows products much easier. There has to be some way to build a skeleton virtual appliance that you could somehow shoehorn your own copy of Windows into . . . anyone?
Anyway, Groundwork Monitor 5.2.1 is built on Centos Release 5 and licensed under the GNU Public License (GPL v2). The actual management system is, as I mentioned, based on Nagios 2.10 (not the latest release of Nagios -- Version 3.03 was released on June 25 this year) along with Nmap, Sendpage, PHP, Apache, MySQL, Cacti, dojo, fping, Ganglia, NeDi, Net SNMP, NRPE, NSCA, Ntop, Perl, PHP, RRDtool, SNMPTT and SYSLOGNG. Nagios also supports its own plug-ins along with the ability to integrate any command line program to work as an application to extend Nagios.
What this melange produces is a very powerful and a complex set of tools that supports role-based management, device monitoring, event detection, reporting with escalation, and mapping, with device discovery and multiplatform implementation along with both agent and agentless client support.
While the Community Edition is available as RPMs for SUSE and Red Hat Enterprise Linux, .debs for Debian and Ubuntu distros, as well as a bootable ISO image based on Centos available for download, it's the virtual appliance for VMware that is the simplest and fastest way to evaluate Groundwork Monitor.
Once you have downloaded the GZIP'ed tarball and unpacked it you simply open the virtual machine with any of the VMware systems (VMware Server, VMware Workstation or the VMware Player) and start it. Voila !
Access to the Groundwork Monitor system itself is through a Web browser, and while you probably won't need to log in to the guest operating system in the virtual machine, should you decide to do so and go looking for the root password let me save you an hour of research: It is 'opensource' (I couldn't find this gem in the documentation anywhere -- what would we do without Google?).
Using the default administrator account, you can log in; create users, roles and groups; play with the example devices already set up; remove them; run the network discovery process; add devices; set up alerts; generate reports; and so on.
Groundwork Monitor Community Edition really can do more or less everything you need in a network monitoring and management environment and can be used to manage systems right up to enterprise-class networks. But be warned; the learning curve for Groundwork Monitor is significant. On the other hand, being wrapped up in a ready-to-run virtual appliance at least makes the complexity of installation a nonissue and is a great starting point for a custom installation.
Now for the downside: As I wrote, Groundwork Monitor provides an enormous range of services but being built from multiple independent projects it is consequently very complex. The result is that the Groundwork Monitor user interface is not the best organized or easiest to understand. There is a lot of embedded help but the system could really do with a lot more.
Bottom line: Groundwork Monitor Community Edition (particularly in its virtual appliance form) is a powerful, flexible and comprehensive network monitoring and management solution. Definitely worth a serious look if you're running a serious network.