I have a Windows 2003 VPN server in my head office and Windows XP VPN clients in my branch office. VPN connections worked fine when my head office was connected to the Internet over dial-up; clients used dyndns.org to find the IP address of my VPN server. But VPN connections stopped working when I upgraded my head office to connect to the Internet using DSL. My headoffice uses an SMC DSL Modem/Router with NAT enabled; my branch office uses a Lucent Pipeline. What do you suggest?
It sounds like your new DSL Modem/Router isn't configured to pass incoming VPN connections to your Windows 2003 VPN server. I don't know which SMC router you're using at your head office, but I'll guess you're using the Barricade Cable/DSL Broadband Router (SMC7004VBR).
Use the Advanced Settings configuration panel on that router to enable "VPN Pass-Through." You'll also need to add your Windows 2003 VPN server as a Virtual Server using the router's NAT configuration panel, specifying the control port used by your VPN as the trigger port. For example, L2TP VPNs use port 1701; PPTP VPNs use port 1723. Also, your VPN clients must send their VPN connection requests to the DSL router's IP address, not the Windows 2003 server's private IP address. You may not need to use dyndns.org anymore if your DSL router has been assigned a static IP address by your provider.
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