Here's my set up:
I have a Firewalled Cisco Router provided by my ISP. (I do not manage this)
I have a Windows 2003 Domain server behind the firewall.
I need for my users to be able to access the domain server from outside the firewall.
I can have an external IP bound to the internal ip of the Domain Server through the router.
My ISP wants to know what port(s) they need to open to allow VPN access through. I have no idea. Is there a standard port? Please help.