yes, away from home.
I’m lucky because my provider offers a static IP address to reach my home, but anyway if your doesn’t you can use a service like DynDNS (dynamic external IP address -> yourName.dyndns.com)
I followed this tutorial to “see” from the internet my AirPortExtreme attached USB drive
-> Method 3 is working for me: just open a 548 port on your router (teh guide say to map 8888 port to 548; I did 548 to 548, it is the same).
If the links doesn’t work:
Method #3: Using Port Mapping
If the 802.11n AirPort Extreme Base Station (AEBSn) or Time Capsule (TC) is connected directly to the broadband Internet modem, verify that the modem is in bridge mode, i.e., if the modem provides NAT & DHCP services, disable them.
If the AEBSn or TC is downstream of another router or gateway device, configure that device for port mapping/forwarding to the AEBSn or TC. (Note: AFP requires that TCP port 548 be mapped.) Also, configure the AEBSn or TC to have a static Private IP address so that it will always be found at the same address.
Use CheckIP (or equivalent) to determine your router's current Public (WAN-side) IP address.
Start the AirPort Utility > Select the 802.11n AirPort Extreme Base Station (AEBSn,) and then, note the IP address shown.
Select Manual Setup.
Verify that Connection Sharing = Share a public IP address is selected on the Internet > Internet Connection tab.
Select Disks, and then, select File Sharing.
Verify that both the "Enable file sharing" and "Share disks over WAN" options are enabled.
Verify that Secure Shared Disks = With a disk password. (Recommended)
Verify that AirPort Disks Guest Access = Not allowed. (Recommended)
Select Advanced, and then, select the Port Mapping tab.
Click the plus sign to add a new port mapping.
For Service, select the "Personal File Sharing" option.
In the Public UDP Port(s) and Public TCP Port(s) boxes, type in a 4-digit port number (e.g., 8888) that you choose. In the Private IP Address box, type the internal IP address of your AEBSn that you wrote down in step 1. In the Private UDP Port(s) and Private TCP Port(s) boxes, type 548. Click Continue.
In the Description box, type a descriptive name like "AirPort Disk File Sharing," and then, click Done.
Click on Update.
To connect to the shared AirPort Disk from a remote location using a Mac:
From the Finder > Go > Connect to Server.
Enter the DynDNS-provided Domain Name or Public (WAN-side) IP address of the AEBSn, followed by a colon and the Public port number that you choose in step 11 of the previous procedure. For example: afp://www.mydyndnsdomain.com:8888 or afp://123.456.789.123:8888
You should be prompted for your user name and password. The user name can be anything you like; the password should be the Disk password for the AEBSn that you created in step 6 previously.