I have a Linode VPS that I use to host multiple sites. I run Ubuntu 10.04 and Apache 2. What I would like to do is have my live sites (example-site.com) and test sites (test.example-site.com) on the same box but have test.example-site.com only accessible when connected to my VPS via VPN.
I have setup OpenVPN following Linode's instructions and am able to connect, but I am not sure how to setup Apache to enable this. How do I setup Apache to only allow access to test sites when connected to VPN, but allow anyone to access the live sites?