1) Insert SIM card into a SIM slot 1.
2) Power up Digi TransPort.
3) Open a web browser and connect to Digi TransPort using the default IP address of 192.168.1.1.
4) Once you are logged into the web interface, select Wizards under the home page, and then select radio button for Carrier Switching Wizard, as shown in the screenshot below:
5) Select AT&T on the next screen and then click next:
NOTE: The carrier firmware download may take few minutes to fully complete. Do not navigate away from the screen while the firmware download is in progress
6) Once the firmware download completes, navigate to Configuration – Network > Interfaces > Mobile > Mobile Settings, and locate the section titled Service Plan/APN. In this field, enter in the APN provided by the carrier, as shown below:
7) Click on the Apply button and then Save the changes to flash.
NOTE: It might take few minutes for device to get an IP address from the carrier when activating the device for the first time. The Mobile IP address should appear under the Cellular section on the home page once obtained, and the Link/Service LED should go solid on the device: