Problems: VPN behind Linksys router

Hey guys,

I've had a lot of difficulties setting up a VPN through my NAT router.
I've searched usenet for a few days, collected a good deal of information
on Linksys and other websites. But I've read conflicting reports about
Linksys routers. Some say they can't let VPN traffic through, while others
say they work great with VPN. Anyway, I can't make it work, I'm quite
confused, and I would greatly appreciate if someone could shed some light
on this issue.


My LAN (LAN1):

- 3 Windows 2000 Pro SP4 workstations including one acting as an FTP and
VPN Server. Norton Internet Security 2003 is deactivated. Each computer
has a fixed local IP address.

- These are connected to the Internet through a Linksys Router BEFW11S4
(firmware version 1.45, 28/02/2003). The router has a dynamic WAN IP
address assigned by my cable ISP.

- Each LAN workstation runs the DNS2go service, effectively giving each of
them an independant DNS name (xxx.dns2go.com) but giving away the same WAN
IP address. This allows me to remotely access the router configuration
utility, or the computers (with VNC), whenever one or more LAN computers
is on.

- On the VPN server, two VPN are created. One with the Windows 2000
connection wizard ("allow incoming VPN connections"), for tests purpose
only since it can only accept a single client connection. One with the
more powerful standalone software WinGate VPN.

- Router's configuration:

I forwarded ports 47, 50, 137-139 (for NETBIOS browsing), 1701 (for L2PT),
1723 (for PPTP), 808-809 (seem to be required by WinGate VPN) to the VPN
server's IP. For these I selected UDP and TCP protocols. Multicast, IPSec,
PPTP passthroughs are enabled. Block WAN Request is disabled following
Linksys instructions. There is no SPI option to enable or disable.


The VPN client

- Windows 2000 Pro SP4 laptop on a LAN (LAN2) behind a proxy computer
connected via ADSL to the Internet. I have no authorization to access and
modify settings on this router computer. NIS 2003 is deactivated on the
laptop.

- A VPN connection is created with the Windows 2000 Connection Wizard,
pointing to the DNS2Go name of the remote VPN server (let's call it
vpnserver.dns2go.com)

- Running the "pptpclnt" utility indicates that server's host information
(that is, vpnserver.dns2go.com) are successfully resolved, that
connectivity test to TCP port 1723 is successful and that GRE packets were
received sucessfully.


Everything seems to be fine, but when I try to connect the client to the
VPN server, I get the dreaded error 651: Your modem (or other connecting
device) has reported an error. Putting the VPN server in the DMZ changed
nothing. Forcing PPTP connection in the client's properties changed
nothing. Trying to access the VPN from a LAN client gives me the error
721: Remote server not responding, after apparently verifying username and
password.

Because I don't have a physical access to my LAN (staying in another
country for a few months), I can't try to put the VPN server out of the
LAN and I don't want to risk remotely upgrading the firmware and leave my
LAN users stranded.


I'm at loss guys. Has anyone really successfully set up a VPN behind a
Linksys firewall? If yes, what am I missing?

Thanks for your help!

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