Ive been looking at monitoring for a while. My org didnt have any before i came other than 'whered my yahoo go'. It appears that most packages out there focus on negative monitoring (ie, this service/host was up and now its not). This seems like a valid first step, but what can you look at past that for positive monitoring (ie that port wasnt up, and now it is, or hey look thats a new DHCP host)? I suppose its possible to have a declaration for every single port/network address in nagios, but that seems cumbersome.
Does anyone know of a better tool for monitoring ports/hosts for affirmatively down?