I am scanning my C class network and don't know why not all devices are shown in the scan. Also, the number of scanned devices changes every time.
Please, let me know how to solve this problem.
Not all IP addresses are listed That would be because not every IP address has network device associated with it. It could also mean some devices are firewalled. Try setting the ping method to Both ICMP and ARP and tick Display inactive devices.
A different number of devices is found in each scan This can happen over time when some devices go off-line and new devices come on-line. To make sure all devices are detected, use Both ICMP and ARP method, and increase ping timeout and the number of attempts in the scan settings.
Here is a screen shot of the settings mentioned above:
@JS, we had this problem and discovered that the anti-virus installed on the workstation was blocking our scans because it thought it was an attack. It was set to block for 5 minutes the first time around then 15 minutes the next time around. It would take about 15 minutes to do a full scan of the networks so each scan would have different results. I don't know if this is your case but I hope it helps in finding the issue. -WS