1. Install ppp
yum install ppp
2. Download pptpd rpm
wget http://poptop.sourceforge.net/yum/stable/packages/pptpd-1.3.4-2.el6.i686.rpm
3. Set the local and remote ip in /etc/pptpd.conf
vi /etc/pptpd.conf
localip
remoteip < range of ip addresses to be assigned to users,