PPTP masquerading and multiple connections

[A van der Veen]

I hava got a problem with NAT and PPTP.
This is the situation:

Clients:
/---------------\
| |
192.168.79.119 ----------| router |
| 192.168.79.1 |--------- internet ----- PPTPD
192.168.79.101 ----------| |
| |
\---------------/

So I want 2 clients connect to a PPTP server somewhere on the internet.
The PPTP server has a public IP adress and accepts multiple PPTP clients.
I can connect with 1 client to the pptp server. Everything works fine,
so I can imaging that my iptables is ok. I can ping the PPTP server and
local ip addresses on the VPN.
I installed the ip_conntrack_pptp kernel patch, compiled a new kernel
(2.4.19 from kernel.org) and installed it.
The ip_conntrack_pptp module is loaded om my machine.

So far everything is ok according the VPN Masquerading howto.

Now I want a second client to connect to the PPTP server. This works ok
since I installed the kernel patch. From the moment I connected the 2nd
client, I cannot ping the VPN anymore from the first client. After a few
second (10 or so) I also cannot ping anymore from the 2nd client. The
strange thing is that the Windows clients (both) keep up the VPN
connection and do not drop it. Not even after a few hours. So they keep
sending and receiving the keep-alive messages. Only pinging (and other
network traffic) is not possible anymore.

Can someone help me out?

Arjan