How to set up a VPN server (PPTP) with CentOS
Have the resources on the local network even when you are physically out of the office is a goal within reach of any system administrator. Just a machine with CentOS, just and open source software are some tips to configure all the best.
As anticipated at the beginning, the technique proposed here is not exactly “old hat”. Consequently, there are many aspects that may hinder the proper functioning of the VPN.
This page of the official documentation offers a wide array of tests, tips and solutions to various problems: I have summarized below the most common.
The client can not connect
If the service is started (you can check quickly by giving service pptpd restart), but clients can not connect, it means that there is some “barrier”.
Move the two computers within the same LAN and try again: If it works, almost certainly means that you have properly configured the router.
Otherwise, the firewall may not let the traffic properly: try to disable it temporarily (perhaps by disconnecting everything from the Internet to prevent security problems!) And try again.
The connection is established but the computer does not see
If the VPN connection is established correctly, but PCs are not accessible, could be a configuration problem.
On the client, run ping 192.168.0.201 (substituting the appropriate IP address of VPN server) and Make sure you get a response.
If not, run yum install tcpdump-y on the server to install a software-capture packets, then proceed with tcpdump-n-i ppp0 and try again to ping: If the terminal does not appear to informational messages, means that the client is not “talking” in any way with the server.
Server and VPN client are spoken, the VPN client and PC LAN no
Trace the cause of this problem is far from easy.
Check that the server itself is having problems communicating with other PCs on the LAN and, perhaps, try to download an updated version of the script routing.
Unable to access files and printers
If everything works, but you can not share resources, you have probably a problem with the specific features of Windows: See the article “Setting up a computer network (LAN)” for more information.