The applications to which I have put this router are far too complicated to explain and I'm really not looking for alternative solutions. There are multiple VPN connections involved, one LAN-to-LAN and the others computer-to-LAN, SIP connections to a PBX involving a remote phone that has to connect through the client VPN router that, in turn, is a client on another LAN over which I have no control. The new router, along with the client router, was purchased specifically because it could (in theory) support the configuration I have to use. I've got the client router and phone working just fine, but limitations in both the Windows VPN pptp client and the new router are problematic, which is why I'm looking for an alternative PPTP client for the computers that have to connect. Though I'm hardly an IT professional, I have a pretty good idea what I'm doing, so it's not just a question of changing some settings on the new router.
Edited to add:
I've been fooling around with this for a couple of weeks (as time at my office allows). I've managed to get most everything I need working, with the primary exception of needing to supply a hard-coded DNS IP address for the Windows PPTP client as a consequence of what both the router and the Windows client allow to be configured so that the client computer doesn't use the router's gateway and internet connection. If I have to live with that, I will, but one of the client computers is headless and configured to automatically connect via VPN, so fiddling with the client is not really an option unless either I go there or I talk the person who uses it (a Luddite
) through hooking up a keyboard and monitor and then accessing the VPN adapter settings to hard-code a DNS address, something I'd really like to avoid.