One need to follow below mentioned steps to install VPN server on windows 2003 server:
1. Go to Start > Administrative Tools > Routing and Remote Access.
2. Right-click on servers icon -> select "Configure and Enable Routing and Remote Access" to start the Setup Wizard
3. Click Next
4. Select "Remote Access (dial-up or VPN)"
5. Click Next.
6. Check the VPN check box and then click next.
7. in the "VPN Connection" window, select the network interface is connected to the Internet and click Next.
8. In the "IP Address Assignment window", there are two options available:
*Automatically Choose this option if you have a DHCP server.
*From a specified range of addresses Choose the option if the remote clients can only be given an address from a specified pool of addresses.
9. Select default value of No, use Routing and Remote Access to authenticate connection requests and click the Next.
10. Click Finish to turn on RRAS and to configure the server as a remote-access server.
Note: One must have to setup RRAS and turn on the service for VPN server.