Most VPNs rely on tunnelling to create a private network that reaches across the Internet. Essentially, tunnelling is the process of placing an entire packet within another packet and sending it over a network. The protocol of the outer packet is understood by the network and both points (called tunnel interfaces), where the packet enters and exits the network.


Depending on the type of VPN, remote-access or site-to-site, you will need to put in place certain components to build your VPN.

• Desktop software for each user
• Hardware such as a Firewall
• VPN server for dial-up services
• Windows RAS for remote users

Firewalls
A firewall provides a strong barrier between your private network and the Internet. You can set firewalls to restrict the number of open ports, what types of packet are passed through and which protocols are allowed through. Some VPN products can be upgraded to include firewall capabilities by running the appropriate firmware upgrade on them. You should already have a good firewall in place before you implement a VPN

Encryption
This is the process of taking all the data that one computer is sending to another and encoding it into a form that only the other computer will be able to decode.