Setting up an ad hoc network on a Mac computer that has an AirPort wifi card in order to share internet access when that computer is connected to the internet via VPN. The following will work ONLY if your Mac computer (1) has an AirPort wifi card and (2) connects to the internet via an ethernet cable connected to the ADSL modem [or possibly through a 3G USB internet connection device]. [This ad hoc network procedure will not work if your computer only connects to the internet via a wi-fi network (like AirPort Extreme or AirPort Express); and it will not work if your computer connects to the internet via an ethernet cable to the ADSL modem but does not have its own wi-fi card.] If you want to have your computer's AirPort card connect to an existing AirPort Express or AirPort Extreme network, the procedure below will have to be done each time you want to use Apple TV, including sharing photos and music via iTunes. [Re iTunes access via Apple TV: for the Home Sharing setting to work, you have to use your Apple/iTunes ID and password, and these might fail if Apple TV knows you're not in the USA.] However, although there seem to be a lot of steps, the whole set up takes less than a minute once you're familiar with it.
1. Enable your VPN connection in Network Settings [under System Preferences]. This means connecting to the internet via VPN [in my case, StrongVPN (PPTP)]. To do this, in System Preferences>Network, click on your VPN set-up in the list of network connection types [StrongVPN (PPTP) in my case], and then click on the "Connect" button.
2. Then enable Internet Sharing for this VPN connection. To do this, be sure that your VPN connection is connected and selected under System Preferences>Network (which will be the case immediately after carrying out step 1 above); then under System Preferences>View, select "Sharing". Your VPN connection should appear in the "Share your connection from" box; if not, select it from the box's drop-down list. Check the "AirPort" box in the "To computers using" options. [Subsequent times you go through this process, the VPN and AirPort selections will already be selected.] Then check the "Internet Sharing" service box. Before this check box will be activated, a pop-up window will appear saying "Are you sure you want to turn on internet sharing?" with a warning about affecting network settings of other computers, etc. Click on the "Start" button in this pop-up window, and this will create an ad hoc local network with your computer's name in the "Computer Name" box, the "Internet Sharing: On" status light turning green. Your VPN connection should appear grayed out in the "Share your connection from" box, and the "AirPort" box under the "To computers using" box will be checked. This ad hoc network will override the computer's connection to other local AirPort network connection options if you have them [like my AirPort Extreme or AirPort Express networks in my case]. To repeat: this process sets up an ad-hoc local wifi network with the name of your computer. Make a note of this ad hoc network name: this is the wireless network you will choose when configuring Apple TV.
3. Open iTunes on your computer if you will be accessing downloaded movies rented from iTunes, or photos or music from your iTunes library to play on your TV via Apple TV. You must also enable "home sharing" for your iTunes library: iTunes>Preferences>Sharing.
4. Turn on and configure Apple TV only after setting up this ad-hoc shared internet connection with VPN running. Be sure to choose the ad-hoc network and NOT any other wifi networks you may have when selecting the wifi network during Apple TV set-up.
5. For your computer to access other wifi networks you may have when you're NOT using the Apple TV, you'll have to reconfigure the computer's AirPort settings after you're done using Apple TV. This is easy to do. First turn off your VPN connection by going to System Preferences>Network and, with your VPN connection highlighted in the list of network connections, click the "Disconnect" button. Go to System Preferences>Sharing and turn off (uncheck) the "internet sharing" box that you'll find set up for your ad-hoc network. Then go back to System Preferences>Network, select AirPort in the list of network options, choose your AirPort Extreme/Express network in the "Network Name" drop box, wait a moment until the "Apply" button in the lower right corner becomes active (ceases being grayed out) and and click Apply. The AirPort network status light will turn green (previously orange), and the Apply button will turn gray. This all takes less than a minute.
