[pptp-server] How to route it?

[Simon Yuen]

I am a beginner on Linux. I have a quesiton on routing.
Following is my network:

ppp 172.16.66.2             172.16.66.20
 [Client(Win98)]-----[PPP/PPTP Server Linux]-----[remote machine(NT)]
vpn 192.168.0.234         192.168.1.234                       192.168.1.235

I started up a pptp server on Redhat7.2 successfully. After I dial up to the
PPP server, I could ping the server and internet.
However, when I connected with VPN behind the ppp, I can ping the server but
I can't ping the remote machine and internet.
What should I do?
If the remote machine IP changed to 172.16.66.x, what should I do?
Thank a lot.