I have installed the community edition. I can scan public IPs that do not have hardware firewall, however it fails to scan any IPs behind the remote hardware firewall. Nmap successfully scan IPs behind the hardware firewall. Do I need to make any specific configuration change to the configuration?
You can set “assume” alive, this might take ages to finish and you will only see what is visible from the other site of the firewall. The commercial correct way would be buy a Greenbone Appliance and place a Scan-Sensor on the other side of the firewall.