Hi Uma,
That looks fine. The sandbox should be able to ping out to the internet as long as your machine has web access. As far as the tutorial you are using, are you running the vagrant command within the sandbox ? If so, that is not what the instructions intend to do. Sandbox already has ambari installed, you just need to start it. If you go to Hue interface, there should be an enable button to turn on ambari or you can download latest HDP 2.3 sandbox which has ambari on by default. If you are running the vagrant command, you need to run it locally on your host machine.
Hope that helps.
Regards,
Robert