As far as the XBee Cellular modules are concerned, the same commands are used to both function on a Digi interface board as it would on your board. That is to say, there are no special commands you need to use that tells the radio to obtain an IP address that are different than what you would use on the interface board. To be more specific, as long as you have a valid SIM card entered, the correct APN, the antennas connected and the proper power, it will provide an IP address once connected to the tower.