LanSweeper. It's the primary asset tracker/scanner we use for our local network of over 3000 network devices. It can read switch data to even provide a means of finding what port a device is connected to on a switch. Combine with ArcGIS to physically trace thousands of network cables and hundreds of fiber trunks and runs, we're able to have immediate access/knowledge of where any asset is located virtually and physically as well as the entire physical path between each point. These two tools have allowed us to migrate from knowledge only being saved in the memory of a few individuals to being preserved via documentation.