From your description seems like you want to implement Different subnets In your network. On ErLite3 there are 3 ports eth0 eth1 and eth2. One of these will be your wan port (to internet). And on rest 2 ports you can set up 2 different networks 192.168.1.x and 5.x...for these you will need 2 different dumb switches or one layer 3 managed switch
However you can also create virtual interfaces(vlan interfaces) under the physical interface feom dashboard and apply you ip addressing information. Kind of like router on a stick version. For this the physical interface will be your trunk and you will need a managed switch and configure your switchport connecting to er lite port as a trunk and allow those 3 vlans.and then you can set up firewall rules to block intervlan traffic. I would suggest you running the wizard first as it automatically creates the wan firewall rules atleast so when you plug ur router in, its secured from internet.
However you can also create virtual interfaces(vlan interfaces) under the physical interface feom dashboard and apply you ip addressing information. Kind of like router on a stick version. For this the physical interface will be your trunk and you will need a managed switch and configure your switchport connecting to er lite port as a trunk and allow those 3 vlans.and then you can set up firewall rules to block intervlan traffic. I would suggest you running the wizard first as it automatically creates the wan firewall rules atleast so when you plug ur router in, its secured from internet.