Symptom
From a public IP address, Apple Remote Desktop is unable to connect to a client that is behind a NAT router. This alert message appears:
"There was a problem communicating with (IP Address)."
Solution
Use the following troubleshooting steps:
1. Make sure the client is set up properly and works with an Apple Remote Desktop admin computer on the local, private network. If this does not work on the local network, then it will not work from across networks. If the client can be controlled from an Apple Remote Desktop admin computer on the local network, continue to step 2.
2. Check that the NAT router's IP address is correct, and that port mapping is working. You can do this by setting up a Web server on the internal network and mapping port 80 to the internal IP address of this server. In Mac OS 9, the default Web server is Personal Web Sharing. In Mac OS X, the default Web server is Apache. Be sure that a client on the private network can load pages from the Web server, then test the connection across networks.
3. Verify that the router hardware (including AirPort Base Station) has the latest firmware installed. Check with the hardware manufacturer for the latest version.