Summary

A VPN is a useful tool for extending the reach of a local network. You can use this tool to give individual remote users, or entire remote networks, access to nonpublic servers on your local network. This is an extremely useful tool when you want to support telecommuting or when you want to tie together two or more networks at distant locations, in order to share servers or otherwise integrate those networks. Several VPN products exist, and many of these are available for Linux. Two particularly popular protocols are PPTP, which is implemented in Linux by PoPToP and PPTP-Linux, and FreeS/WAN. PPTP is commonly used by individual remote clients to link to a central network, while FreeS/WAN is more commonly used to tie together entire networks. Both can be used in either way, though. Before you implement a VPN, you should carefully consider the security implications of doing so, paying particular attention to the fact that each VPN client is another potential entry point to your local network.