In the large and bewildering world of network managers, we are inching ever-closer to the network administrator's ultimate dream: magic network monitors that show you the data you want and alert you to only the important problems without making configuring the monitor your life's work. Does Zenoss cross that magic threshold? Not quite, but it's an excellent network monitor, anyway.
Installation is the weak point of most network monitors. They have complex dependencies and don't provide a nice easy "appliance" bundle, so it can take a fair bit of hair-pulling to put all the pieces together. Zenoss offers several installation options: source tarballs, RPMs and a VMware virtual appliance for either Linux or Windows. The source installation provides a nice install script, so it's not too bad. Zenoss requires Python and MySQL, and you must be sure to have the correct versions.
Once Zenoss is up and running, it has a stylish Dashboard form factor no room for stodginess in Zenoss. Zenoss is good at discovering and inventorying network devices all by itself, and of course you can tweak it manually to your heart's content. By default, Zenoss uses SNMP to poll devices. It can also run portscans to discover services. Adding new devices manually is easy. Simply enter the Device Name and Device Class, and Zenoss fills in the rest.
Its database is stored in a Zope Enterprise Object (ZEO) database, which Zope bills as scalable, distributable and capable of handling large loads.
Viewing status information is flexible. You can view your network by groups and drill down to individual devices with a few mouse clicks. It stores historical data, so you can go back in time and figure out what happened when you weren't looking. It offers flexible reporting features, so you can generate reports based on just about any data Zenoss stores. It offers the usual options for sending alerts, and the Web form for configuring alerts makes it easy to customize them.
Zenoss is a free download and free software licensed under the GPL. It has good documentation and an active user community. You may also purchase commercial support and training, and custom services.