We've shown you how to roll your own VPN using Hamachi, and even how to set up Privoxy to secure your web browsing once you have your personal VPN set up. Hamachi isn't the only option: you can also download and configure OpenVPN (a free SSL VPN) on your own home server,, or if you have a router that supports it, enable OpenVPN on your home router so you can connect back to it when you're abroad. Combined with Privoxy, you get the privacy and anonymity benefits of a VPN without spending a dime.Both of these options put control in your hands, and while they're not quite as anonymous as subscription methods or offer international exit locations, they do give you the the most important benefits of a VPN: security, privacy, and anonymity while you're away from home.
Samara Lynn is Lead Analyst, Networking and Small Business at PCMag.com
Example use of a VPN Tunnel
The following steps  illustrate the principles of a VPN client-server interaction in simple terms.
Assume a remote host with public IP address 126.96.36.199 wishes to connect to a server found inside a company network. The server has internal address 192.168.1.10 and is not reachable publicly. Before the client can reach this server, it needs to go through a VPN server / firewall device that has public IP address 188.8.131.52 and an internal address of 192.168.1.1. All data between the client and the server will need to be kept confidential, hence a secure VPN is used.
- The VPN client connects to a VPN server via an external network interface.
- The VPN server assigns an IP address to the VPN client from the VPN server's subnet. The client gets internal IP address 192.168.1.50, for example, and creates a virtual network interface through which it will send encrypted packets to the other tunnel endpoint (the device at the other end of the tunnel). (This interface also gets the address 192.168.1.50.)
- When the VPN client wishes to communicate with the company server, it prepares a packet addressed to 192.168.1.10, encrypts it and encapsulates it in an outer VPN packet, say an IPSec packet. This packet is then sent to the VPN server at IP address 184.108.40.206 over the public Internet. The inner packet is encrypted so that even if someone intercepts the packet over the Internet, they cannot get any information from it. They can see that the remote host is communicating with a server/firewall, but none of the contents of the communication. The inner encrypted packet has source address 192.168.1.50 and destination address 192.168.1.10. The outer packet has source address 220.127.116.11 and destination address 18.104.22.168.
- When the packet reaches the VPN server from the Internet, the VPN server decapsulates the inner packet, decrypts it, finds the destination address to be 192.168.1.10, and forwards it to the intended server at 192.168.1.10.
- After some time, the VPN server receives a reply packet from 192.168.1.10, intended for 192.168.1.50. The VPN server consults its routing table, and sees this packet is intended for a remote host that must go through VPN.
- The VPN server encrypts this reply packet, encapsulates it in a VPN packet and sends it out over the Internet. The inner encrypted packet has source address 192.168.1.10 and destination address 192.168.1.50. The outer VPN packet has source address 22.214.171.124 and destination address 126.96.36.199.
- The remote host receives the packet. The VPN client unencapsulates the inner packet, decrypts it, and passes it to the appropriate software at upper layers.
RoutingTunneling protocols can operate in a point-to-point network topology that would theoretically not be considered a VPN, because a VPN by definition is expected to support arbitrary and changing sets of network nodes. But since most router implementations support a software-defined tunnel interface, customer-provisioned VPNs often are simply defined tunnels running conventional routing protocols.
PPVPN building-blocksDepending on whether the PPVPN (Provider Provisioned VPN) runs in layer 2 or layer 3, the building blocks described below may be L2 only, L3 only, or combine them both. Multiprotocol label switching (MPLS) functionality blurs the L2-L3 identity.
- Customer (C) devices
- Customer Edge device (CE)
- Provider edge device (PE)
- Provider device (P)