Build server outside of firewall

Hi,

I'm wondering what the minimum considerations are for a build server outside of our firewall. Do the build server and the App tier need IP connectivity, for example, through a VPN?

If there is no IP connectivity, i'm assuming it just wont work?

And one more thing ..are these ports still relevant: http://solutionintegrator.blogspot.nl/2010/05/tfs-2010-build-server-complex-firewall.html

Cant find anything on Technet,

cheers,

Jon