[nznog] Network device discovery

Hi guys. I'm looking for software that will discover network devices site-wide, as the start-point for an asset management db. Looking for MAC and IP primarily, but if manufacturer\model would be great too. Having command line execution, connectivity diagram output and being opensource\free, would all be a bonus. Not looking forward to having to do it manually, so what's out there to make life easier? Almost time for a beer. Thanks, Paul.