You can enable a gateway for an out-of-band drop interface by using the Network Security appliance Web UI or CLI:
Configuring the gateway using the Web UI
Configuring the gateway using the CLI
When you use ether1 or ether2 as the out-of-band drop interface and the Network Security appliance is connected to a next-hop L3 device, this feature configures the next-hop IP address to reach the original client or the server network.
Prerequisites
Administrator or operator access to the Network Security appliance.