OS X: Using and troubleshooting Back to My Mac with your iCloud account

Back to My Mac requirements:

• An iCloud account.
• Two or more Macs running OS X Lion v10.7.3 or later that are configured to use the same iCloud account.
  
Note: For the best user experience with Back to My Mac, update your Macs to OS X Lion v10.7.4 or later.
• Screen sharing requires a 300-Kbps or faster, bi-directional Internet connection (up/down) between the computers. (File sharing may be usable with slower connections).
• An AirPort base station (an Airport Extreme, Airport Express, or Time Capsule), or a third-party Internet router which supports UPnP or NAT-PMP, with the latest available firmware installed (version 7.6.1 or later for AirPort).

Note: Some firewalls, such as those at a large organization, may not allow certain Back to My Mac connections. For example, you may not be able to contact your Mac at work from home, but you may be able to contact your Mac at home from work. Check with your organization's network administrator.  

Setting up and using Back to My Mac

Use OS X Help for information about how to set up and use Back to My Mac: 

1. From the Finder, click the Help menu.
2. When the Help Center appears, type "Use Back to My Mac" in the search window.
3. Choose the Help article titled "Use Back to My Mac."

Troubleshooting Back to My Mac

If Back to My Mac is not working as expected, try the troubleshooting steps below, if they apply.

• Update all your Macs to OS X Lion v10.7.3 or later (OS X Lion v10.7.4 or later is recommended).
• Choose System Preferences from the Apple () menu. Open iCloud System Preferences and check that Back to My Mac is enabled. See if any diagnostic messages are provided under the Back to My Mac section to assist you with troubleshooting and resolving any connection issue. 
• Toggle Back To My Mac off and back on by deselecting and then reselecting Back To My Mac in iCloud System Preferences. 
• Make sure the computer you are trying to connect to is not sleeping and is set to Wake on Demand. For more information about Wake on Demand, see this article.
  
• If you are using an AirPort base station, make sure your firmware is up-to-date (open AirPort Utility 6.0 or later).
• Check your network for a multiple NAT setup and reconfigure your network as needed.
• Make sure NAT-PMP or UPnP is enabled (if you are using an AirPort Extreme Gigabit Ethernet base station, click here for information about AirPort Extreme Gigabit Ethernet and NAT PMP).
• Ensure TCP port 5354 and UDP ports 4500 and 5353 are open on your firewall. To learn more about ports used by Apple products, click here.

Additional troubleshooting for Back to My Mac connection issues after moving a MobileMe account to iCloud 

Note: Perform these steps only if you've verified the information in the previously listed troubleshooting section is configured correctly.

1. Open Keychain Access located in /Applications/Utilities.
2. Choose the System Keychain in the Keychains list on the left.
3. Sort the Keychain list by Kind.
4. Select all keys listing the "Back to My Mac Key."
5. Delete the selected keys. You will be prompted for your machine's administrator password.
6. Quit Keychain Access.
7. Choose System Preferences from the Apple () menu. Open iCloud System Preferences.
8. Toggle Back to My Mac off and back on again by deselecting (if still selected) and selecting the checkbox.
9. Once Back to My Mac connects, quit System Preferences.

If you still are unable to use Back to My Mac reliably

Contact iCloud Support. Be sure to provide the following information:

1. A detailed description of your network setup for each computer, including router types or models and modem brands.
2. The details or screenshots of any diagnostic messages provided in the Back to My Mac System Preferences pane. (For assistance with screenshots, see this article for OS X Lion or this article for OS X Mountain Lion.)
3. The results of the traceroute performed on each computer when checking for a multiple NAT setup. (For assistance with capturing the traceroute, see this article for OS X Lion or this article for OS X Mountain Lion.)
4. The Computer Name and Local Hostname of each of your computers.
5. Any other troubleshooting steps you have performed.