System Ferret is a tool that used to be provided by Allen-Bradley for scanning the I/O configuration using RSLinx. It returns useful information such as part number, serial number, firmware version, IP address, etc. about the system.
GIS Ferret Reports
The System Ferret tool is no longer available for download. It has been replaced by the Asset Inventory Agent in FactoryTalk Asset Centre software.
However, someone cleverly stashed a copy of System Ferret in Dropbox.