Add VPN in CentOS
Step 1
1. http://pptpclient.sourceforge.net/#download download the latest version of pptp Client
2. Upload your server.
Step 2
1. tar -zxvf your path
2. your path/pptpsetup --creat <vpnname> --server <vpn-ip> --username<> --password<>
Connect
your path/pppd call <vpnname>
Disconnect
killall pppd
Some note
1. make sure that your serve has installed the ppp
#rpm -qa|grep ppp
2. ppp is in the disk of centos
#rpm -ivh ./ppp-2.4.4-2.el5.i386.rpm