OS X: Back to My Mac requires AirPort base station or UPnP-capable third-party router

Note: For the best user experience with Back to My Mac, update to OS X Lion v10.7.4 or later (use Software Update to download and install the latest updates). Also, make sure your router supports NAT-PMP (NAT Port Mapping Protocol) or UPnP (Universal Plug and Play), and that it's enabled.

The Back to My Mac feature of OS X is designed to work seamlessly with compatible AirPort base stations. Please make sure that your AirPort software is up to date. This seamless integration is achieved through the use of NAT-PMP (NAT Port mapping Protocol) technology, which enables your computer to automatically configure your AirPort base station to provide services between your local network and the Internet.

Some third-party Internet routers use a technology called UPnP (Universal Plug and Play), which is similar to NAT-PMP. Back to My Mac works with both NAT-PMP and UPnP.
 

Back to My Mac may need be enabled

If Back to My Mac isn't working and you use an AirPort base station, here are instructions to turn Back to My Mac on.

1. Open the AirPort Utility (in /Applications/Utilities).
2. Click the AirPort device and then click Edit.
3. Select the Base Station tab.
4. Click the + button in the Back to My Mac section and enter your iCloud username and password and sign in.
5. Click Update to save changes.
6. A green indicator will show under status when a connection is established.
7. Quit the Airport Utility.

If Back to My Mac isn't working and you use a third-party router, make sure UPnP is enabled. Consult the device's documentation or contact the manufacturer for information about enabling UPnP.