Mac OS X: Using and troubleshooting Back to My Mac and MobileMe

Back to My Mac Usage Requirements

• An AirPort Extreme or Express base station, or third-party Internet router, which supports UPnP or NAT-PMP, with the latest available firmware installed (version 7.6.1 or later for AirPort).
• A MobileMe subscription.
• Two or more Macs running Mac OS X v10.5, v10.6, or OS X Lion that are configured to use the same MobileMe account. Mac OS X v10.6.7 or later is strongly recommended, as is having all your Macs on the same OS.
• 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)

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.  

See this article for detailed information about security and Back to My Mac.

Setting up and Using Back To My Mac

See the Back To My Mac Help.

Troubleshooting Back to My Mac

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

• Make sure Back to My Mac is enabled on all computers, and that you have met all of the requirements listed above.
• Open the Back to My Mac pane of the MobileMe System Preferences to see if any diagnostic messages are provided to assist you with troubleshooting and resolving the connection issue (Mac OS X v10.5.3 or later required for this step).
• Make sure the computer you are trying to connect to is not sleeping.
• If you are using Internet Sharing, you may need to turn it off. Find out more about Back to My Mac and Internet Sharing compatibility here.
• Update all computers to Mac OS X v10.5.6 or later.
• If you are using an AirPort Extreme Gigabit Ethernet base station, make sure your firmware is up-to-date (open AirPort Utility 5.6 or later). Learn more about downloading AirPort base station software and firmware. 
• If any of your computers are configured with the same Computer Name, change their Computer names.
• If two of your computers are configured with the same Local Hostname, change the Local Hostname on one of the two computers (this might be the case if your computers were updated from Mac OS X v10.4).
• 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.

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

Contact MobileMe support.  Be sure to provide the following information:

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