If you have followed the instructions on how to install boot2docker on windows you will discover that the docker VM may not able to talk to the outside world by default.
To correct this you have to add port forwarding from the docker VM to the HOST. This is accomplished by the following
Run the newly installed Oracle Virtual box on your window machine
Network > Port Forwarding
Add the docker port (2375) so that it can talk out through the host (windows) machine
With this in place you must close boot2docker and restart the VM.
After that you can restart boot2docker and you should be able to ping the outside world