You could put both virtual NICs on the same vswitch. You could still get NAT to work, but you potentially lose much of the security of IPCop since there is no isolation of the green and red NICs. In a physical install of IPCop, it would be like plugging in both the green and red NICs to the same switch, then plugging in all your computers and the DSL/cable modem to that same switch. IPCop wouldn't care that both NICs are plugged in to the same switch, so long as the computers can see the green NIC on one subnet and the red NIC can see the DSL/cable modem on another subnet. It may be fine for testing and training, but for a production environment or any "real use", it would be best to get a second NIC for the ESX host. Check the compatibility list or vm-help for compatible NICs.
