I have setup a PPTP server on a CentOS 6 box. Several clients (Windows and Linux) connect to this server. All clients use the same subnet. All clients (Win or Lin) can surf the Internet using the VPN successfully. Windows clients can ping any other Windows client (XP/Vista/7) connected to VPN. Linux clients (KVPNC) can ping any Windows client (XP/Vista/7) connected to VPN. So far so good. But there's this weird problem and I've been trying to figure it out with no luck: No client can ping (reach) a Linux client (successfully) connected to VPN. And yes, the firewall is completely disabled. I'd really appreciate any hint/idea. TIA, EDIT: The ultimate goal of this is to share services across the VPN, like accessing a HTTPD running on a Linux box from a Windows client.