If you setup via a router and you are using Engate, do you need two network cards for routing to work?
If you setup your Lotus Foundations as the default firewall/gateway then you can ignore that step. All you need to verify is that you have a ROOT user in user setup, that Eth1 is using a public IP(local network options).
The other option with 2 different nics applies to when you have a ROUTER up front of the Lotus Foundations server and the Lotus Foundations appliance is only plugged into Eth0 only!