Comment by ovation1357

I've been managing multiple instances of the free "Horizon" version of OpenNMS for nearly 10 years, even contributed a couple of bug fixes. It doesn't get much love from coworkers and it's an absolute beast to learn but it generally does the job. It's got a LOT of bells and whistles including support for all sorts of Comms and IT gear. It can be a tad clunky, pretty RAM and I/O intensive (Java) and the vast number of XML config files can be very daunting for new users. But it largely does what's needed including custom detection and status polling of services, recieving and processing SNMP traps and polling SNNP metrics. The built in graphs are useful but a bit old and ugly however it has Grafana integration and one day I'll look into trying that out.

It heavyweight and very "enterprise" - not necessarily going to cut it for home or small business use, but if you've got a huge sprawl of legacy systems and applications then it might be a decent fit for centralised monitoring.