Mac OS X 10.5: Back to My Mac diagnostic messages in Mac OS X 10.5.3 or later

Resolution

Green status light

The Back to My Mac status indicator light is green when there are no connectivity issues and the network configuration is correct. 

Yellow status light

Various conditions may cause the status indicator light to be yellow.  These include network configuration issues, local network restrictions, router and/or modem device restrictions, and issues connecting to the MobileMe service itself.

Here are three conditions that may produce a yellow status light:

1. NAT-PMP or UPnP is not enabled

This alert may appear in MobileMe preferences: "Back to My Mac isn't working properly because it requires a router that supports NAT Port Mapping Protocol (NAT-PMP) or Universal Plug and Play (UPnP). Make sure your router supports one of these protocols and that it is enabled."

This can happen if your Internet router device doesn't support either the NAT-PMP or UPnP connection protocols.  You may also see this message if your router device supports NAT-PMP or UPnP, but it isn't currently enabled.  You may notice that outgoing connections may be successfully made (to reach your other computers registered with Back to My Mac) but that your Mac is not "discoverable" or "visible" from other computers attempting to connect to the Mac displaying this message.

Resolution: Enable UPnP or NAT-PMP using the instructions or software included with your network router device. To learn about AirPort models that support NAT-PMP and how to enable NAT-PMP if necessary using the AirPort Utility, see Mac OS X 10.5: Back to My Mac requires AirPort base station or UPnP-capable third-party router. If you don't have direct access to your Internet router (for example, if you work in a company that has a large network that you don't administer yourself), check with your network administrator.

Notes:

• If the issue persists with an AirPort Extreme Gigabit Ethernet base station, and you have enabled NAT-PMP using the AirPort Utility, update your base station firmware.
  
• To learn if your third-party router device has been tested for NAT-PMP / UPnP compatibility with Back to My Mac and Screen Sharing applications, see the Back to My Mac Supported Devices List.  Some third-party router devices that advertise UPnP compatibility may require a firmware update from the manufacturer.

2. "Double NAT" configurations

This alert may appear in MobileMe preferences: "Back to My Mac isn't working properly because you may have more than one device on your network providing Network Address Translation (NAT). Try disabling NAT on one of the devices."

This message appears when a "Double NAT" configuration exists within your local network devices.  This could occur when at least one router (wireless or wired) is connected to another router, and each is providing NAT.

Note: You may notice that outgoing connections may successfully be made (to reach your other computers registered with Back to My Mac) but that your Mac is not "discoverable" or "visible" from other computers attempting to connect to the Mac displaying this message.

Resolution: See Back to My Mac: "Double NAT" configurations may prevent Back to My Mac connections. Generally, only the primary router device (the one plugged directly into the cable or DSL modem) should be providing NAT service; other connected router devices should not. You can read more about network address translation (commonly abbreviated as NAT).
 

3. MobileMe cannot be reached

If the MobileMe service cannot be reached, you may see this message: "Back to My Mac isn't working properly because there's a problem with your connection to MobileMe."

Resolution: Turn Back to My Mac off and then back on by clicking the "Stop" button in MobileMe preferences, then clicking the "Start" button once it appears.

Notes:

• You might also encounter this issue if outbound TCP connections to port 5354 are blocked by a firewall.  If you're in a corporate network environment (or large institution where the Internet is managed for you) you may need to consult your network administrator if you observe this message.
• If the DNS proxy in your router doesn't support DNS queries for SRV (or SOA) records, you may encounter this issue.  To see if your Apple or third-party router device has been tested with Back to My Mac, please check the Back to My Mac Supported Devices List.
• Some networks may provide connection errors when you attempt to use Back to My Mac with certain types of MobileMe member names. Please see Back to My Mac: Some networks may not recognize some MobileMe members for more information.

Red status light

Back to My Mac requires a valid Internet connection. If you're not connected to the Internet, this message appears: "Back to My Mac isn't working properly because you're not connected to the Internet."

Resolution: Click the "Network Diagnostics..." button to help troubleshoot your Internet connection.

Note: You may also observe this message if your Internet Service Provider (or ISP) is experiencing a service outage, or using a different connection protocol than you have configured in Network preferences.