Dual network interfaces is often part of the requirements for redundancy, however in such cases it is also very common to specify that the behaviour of borth of these should be identical. You see it in subsea control systems where they have an "A" and "B" channel, you see it topside where the device might need to be on two networks etc.
Unfortunately this is not the case for any of the dual port RT targets from NI. The secondary port is really a second class NIC. It has limited configuration options. It does not support DHCP, you cannot specify a gateway for it - and the code to do programmatic changes to its configuration is not easily available.
Please make the two ports fully interchangable. Port 1 or 2? It should not really matter which one you use.