Get help with multiple-NAT configurations for Back to My Mac
If your network includes several routers that provide Network Address Translation (NAT), your Back to My Mac connections might not work properly. The Mac that you're trying to connect to might appear in the Finder sidebar, but you can't connect to it. Or it might not appear in the sidebar at all. You might also see this alert: "Back to My Mac may be slow because more than one device on your network is providing network services."
In these cases, your routers could be providing too many layers of NAT. A multiple-NAT configuration happens when at least one router in the network is connected to another router, and each one provides NAT. For example, if your cable modem is providing NAT, and you connect an AirPort Base Station to the modem using the default AirPort settings, the AirPort Base Station might provide another layer of NAT.
To resolve the issue, follow the steps below. If you're on a corporate network, contact your network administrator for help.
Find out if your network has a multiple-NAT configuration
- Open Network Utility.
- OS X Mavericks: Network Utility is located in /System/Library/CoreServices/Applications. To open Network Utility quickly, search for it with Spotlight.
- OS X Mountain Lion or earlier: From the menu bar, choose Go > Utilities, and double-click Network Utility.
- In the Traceroute tab, enter "icloud.com" and click Trace.
- In the results, look for the line beginning with the number 2. If the address in that line is an IP address in one of these ranges, your network has a multiple-NAT configuration:
If the IP address in line number 2 isn't in those ranges, then you don't have a multiple-NAT configuration. Learn how to resolve other issues with Back to My Mac.
Update your software
Make sure your Macs are using OS X Lion v10.7.5 or later. If the issue continues, follow the next steps.
Turn off NAT on one of your devices
If you’re using your modem as a router, or if you’re not using an Apple router, review the product documentation to see how to turn off NAT.
If you’re using an AirPort Base Station and you can’t turn off NAT on the modem or router, run the base station in bridge mode to turn off NAT:
- From the menu bar, choose Go > Utilities, and double-click AirPort Utility.
- Select your base station and click Edit in the pop-up menu.
- Click the Network button and select Router Mode: Off (Bridge mode).
- Click Update to restart the base station.
Connect to the Internet and try again
After you turn off NAT, make sure that you can connect to the Internet. Then try using Back to My Mac again.
If you still can't connect to your Mac, you can try to resolve other issues with Back to My Mac.