Librenms is a very flexible network and server monitoring and alerting system. I have it deployed at a number of companies based on the ease of installation, the fact that it auto discovers devices, it is updated frequently (typically multiple times a week) and supports pretty much every network device you can think of.
On top of that, the alerting can be tuned to match very specific cases as the back end is MySQL so you alerting conditions can match almost anything you can write a SQL query for. A good example would be to only alert on certain interfaces that have a specific description in them such as “TRANSIT” where the device has a host name of “edge” and is only a 10Gbs connection (the interface name is ‘xe’). Because you can group things by description or part of a host name, you can just say anything with the string “edge” in the hostname should be considered a “edge router” so a group “ER” can be created for these devices. With autodiscovery, as soon as you add a device, it will get automatically be put into the group that the rule/regular expression matches it.
One of the more interesting features is Libre’s API. You can get pretty much any detail you want out of what Libre has collected and stored in the DB. It will also create graphs for you on the fly. One case I have had in the past is to create daily and weekly total bandwidth graphs for a set of specific ports on a group of switches. The switch ports has a particular unique string I can match on so I was able to create a “group” called “peering” that included these ports over all of the switches.
I wrote this simple script called create_public_graphs.sh that asked for a graph for daily and weekly time frames. I also added various options to the request such as don’t show the legend of interfaces and make the in and out directions all one color. The other option is to make different colors for each interface. We wanted a clean look so we went for the solid color. The API doesn’t do everything you may want such as tilting the graph. This is where I use the “convert” program from imagemagick to overlay some text at the top of the graph. You can see the final result at the SFMIX site.