Create an FTP Server
Most Internet service providers catering to small businesses (and consumers, for that matter) provide only one dynamic IP address with their standard service plans. They charge an extra fee for each unique static IP address.
Just as their names imply, a static IP address never changes, while a dynamic IP address does. (The concept of dynamic IP addresses came about because Internet Protocol version 4, or IPv4, was running out of unique addresses. The newer IPv6 has an all but inexhaustible inventory of addresses, but it’s still rolling out.)
The difference between dynamic and static IP address types is unnoticeable--until you try to access your server while you’re on the road, or you attempt to set up an FTP server for file sharing. If your server doesn’t have a fixed IP address, you won't be able to access it via the Internet reliably because its address might change. Fortunately, you have a workaround that’s much less expensive than paying for a bunch of static IP addresses.
Sign up with a third-party dynamic-DNS service provider (Dyn and No-IP are two examples), and you can create a unique and easy-to-remember name for your server--such as freenas.yourcompany.com--that the DNS service provider will map to your dynamic IP address. Your FreeNAS server will automatically update the service each time its IP address changes, so you’ll always be able to connect to the server from the Internet using the unique URL you've created.
Once you’ve signed up with a dynamic-DNS service, log in to your FreeNAS configuration screen, click Services, and then select Dynamic DNS. Choose your service provider from the drop-down list, enter your domain name, and enter the username and password for your dynamic-DNS account. The update period is the interval--measured in seconds--at which your FreeNAS server will update your dynamic-DNS service provider with its IP address. Contact your service provider for a recommendation, as updating too frequently could get you blacklisted.
You’ll also need to configure FTP service on your FreeNAS server, which involves establishing permissions and setting the port that it will use for network connection requests (typically port 21 for an FTP server). Now open the FreeNAS Control Services panel, and turn on FTP and dynamic-DNS services. The final step is to configure your router’s port-forwarding settings so that incoming FTP requests are forwarded to the FTP server running on your FreeNAS server.