I am new to setup linux VPN , I would like to know what tools that I need to setup in both servers ? can I config it with the X windows ? what is the simplest way to setup it ? thx in advance .

http://www.openswan.org/
http://openvpn.net/
http://linas.org/linux/vpn.html - various solutions for VPN in Linux..

http://tldp.org/HOWTO/VPN-HOWTO/
and of course forwarding X over SSH..
http://tldp.org/HOWTO/XDMCP-HOWTO/ssh.html

Lots of different options depending on your needs..

thx reply ,

I have read the link . In my current system, I would like to setup a single ( and simple )VPN with remote office , which site I need to install openvpn ? which site called client side ( my local site or remote office ) ? I know there is somthing called "Masquerade" , do I nned to install it ? if I have firewall ( windows ) in my local office , what I need to do ? thx

It all depends on what you are trying to accomplish..

I connect to my linux machine remotely through SSH. I can copy files across ssh using scp amd do pretty much anything that I need to do from another Linux machine or a Windows PC using Putty and winscp.

A VPN can be used for a Client to Server connection. The Server being the Main machine at the office and the client being the home workstation or your laptop..

A VPN can also be a network to network connection where a Bunch of PC's on one network can talk to a bunch of PC's on another network as if they were all on one large network in the same building.

So explaining exactly what you are trying to accomplish would help you get a more specific response..