A secondary network is a different network that connects to a Firebox interface with a switch or hub. When you add a secondary network, you map an IP address from the secondary network to the IP address of the Firebox interface. Thus, you make (or add) an IP alias to the network interface. This IP alias is the default gateway for all the computers on the secondary network. The secondary network also tells the Firebox that there is more than one network on the selected interface.
To add a secondary network, do one of these procedures:
Use the Quick Setup Wizard
If you configure the trusted and optional interfaces to use the same IP address as the external interface, the Firebox is configured in drop-in mode. In drop-in mode, you can enter an IP address for the secondary network in the Quick Setup Wizard. This is the default gateway for your secondary private network.
Add the secondary network in Policy Manager
If you configure the Firebox in routed mode, or at any time after you use the Quick Setup Wizard, you can use Policy Manager to add secondary networks to an interface.