Setup with 2 IP Addresses

I setup up a freePBX box with one ip address (private)
After the install I then added a 2 IP (public) are there any changes I need to make in order to ensure my system is in good working order.

All my sip phones sit off private interface and the public interface is used for my sip trunk.

One or Two Network Cards?

Bill/W5WAF

2 built in Fast-E ports