To change the IP address range used on the LAN network, go to NETWORK>LAN and then click the EDIT option. Set as shown below and click SAVE&APPLY. When the unit reboots, reconnect and access the web interface at the address you have set. In the example below, we have set the addres: 172.31.0.1 so when we reboot the unit, to access the web interface in our example, we need to write the address http://172.31.0.1

The DHCP range is set automatically, but if they want to check or change this, go back to NETWORK>LAN and click EDIT and the DHCP settings are in the Firewall Settings tab.