Using GFI LanGuard it is possible to scan an IP range of up to 65,535 machines for network discovery. From these machines, a maximum of 15,000 machines found on the network will be scanned.
However it is not recommended to scan more then 2,000 machines in a single scan. This is to avoid that the scan takes too long to finish. A scan on a lot of machines will also generate huge reports which will take a very long time to load.
NOTE: When scanning a range of IPs larger than 65,535, only the first 65,535 will be considered. Any additional IPs will be ignored.