Microsoft Knowledge Base Article 300434 contains the following summary:

This step-by-step article describes how to configure Windows 2000 to allow remote users to connect to your network, including how to allow dial-up connectivity through a modem and a Virtual Private Network (VPN) connection.

The following scenarios are examples of how the client computer connects to a Windows 2000 remote access server:

Client computer <--> Windows server (Dial-up connection)
Client computer <--> Internet (ISP) <--> Windows 2000 server (VPN connection)

These scenarios assume the following configurations:

For dial-up capability, the modems are configured on the server.
For VPN capability, the server has two network cards.
For VPN capability, Point to Point Tunneling Protocol (PPTP) is used for the VPN tunnel.
For VPN capability, the server has a direct connection to the Internet, and is not behind any firewall or proxy servers, or is not running any program that provides these functions.
No routing protocols are configured, such as Routing Information Protocol (RIP) or Open Shortest Path First (OSPF) routing protocols.