VPN passthrough in RedHat 9

Hi all,

I would really appreciate some help regarding an issue I'm having
with a Linux RH9 box. This box is acting as a gateway - and there is
NO firewall on it, so nothing should be blocked. Here is my setup:

WinXP box --------------- Linux Box ------------------- Cisco 800
router ---------------- Internet

I have enabled packet forwarding with the command "echo 1 > /proc/
sys/net/ipv4/ip_forward", and I have verified it works by surfing the
web, doing remote Desktop from the XP box, doing a remote desktop to
the XP box, etc. everything works fine; except....

When I launch a PPTP VPN connection from the XP box to connect to a
VPN server out on the web, I keep getting: "Error 800 Unable to
establish the VPN connection. The VPN server may be unreachable or
security parameters may not be configured properly for this
connection."

I know the VPN server is available and that my security parameters
are just fine, because when I bypass the Linux box, the VPN connection
establishes without any problems.

I don't know what to check. There is no firewall, Port forwarding
is on... what else is there?

Al

Al wrote:
> Hi all,
>
> I would really appreciate some help regarding an issue I'm having
> with a Linux RH9 box. This box is acting as a gateway - and there is
> NO firewall on it, so nothing should be blocked. Here is my setup:
>
> WinXP box --------------- Linux Box ------------------- Cisco 800
> router ---------------- Internet
>
> I have enabled packet forwarding with the command "echo 1 > /proc/
> sys/net/ipv4/ip_forward", and I have verified it works by surfing the
> web, doing remote Desktop from the XP box, doing a remote desktop to
> the XP box, etc. everything works fine; except....
>
> When I launch a PPTP VPN connection from the XP box to connect to a
> VPN server out on the web, I keep getting: "Error 800 Unable to
> establish the VPN connection. The VPN server may be unreachable or
> security parameters may not be configured properly for this
> connection."
>
> I know the VPN server is available and that my security parameters
> are just fine, because when I bypass the Linux box, the VPN connection
> establishes without any problems.
>
> I don't know what to check. There is no firewall, Port forwarding
> is on... what else is there?

IP masquerading?

Al wrote:
> Hi all,
>
> When I launch a PPTP VPN connection from the XP box to connect to a
> VPN server out on the web, I keep getting: "Error 800 Unable to
> establish the VPN connection. The VPN server may be unreachable or
> security parameters may not be configured properly for this
> connection."
>
> I know the VPN server is available and that my security parameters
> are just fine, because when I bypass the Linux box, the VPN connection
> establishes without any problems.
>
> I don't know what to check. There is no firewall, Port forwarding
> is on... what else is there?

modprobe ip_nat_gre

>
> Al
>