Vpn; Overview; Vpn Usage - D-Link NetDefendOS User Manual

Chapter 9: VPN
This chapter describes the Virtual Private Network (VPN) functionality in NetDefendOS.
• Overview, page 667
• VPN Quick Start, page 671
• IPsec Components, page 683
• IPsec Tunnels, page 701
• PPTP/L2TP, page 729
• L2TP Version 3, page 741
• SSL VPN, page 752
• VPN Troubleshooting, page 762

9.1. Overview

9.1.1. VPN Usage

The Internet is increasingly used as a means to connect together computers since it offers
efficient and inexpensive communication. The requirement therefore exists for data to traverse
the Internet to its intended recipient without another party being able to read or alter it.
It is equally important that the recipient can verify that no one is falsifying data, in other words,
pretending to be someone else. Virtual Private Networks (VPNs) meet this need, providing a
highly cost effective means of establishing secure links between two co-operating computers so
that data can be exchanged in a secure manner.
VPN allows the setting up of a tunnel between two devices known as tunnel endpoints. All data
flowing through the tunnel is then secure. The mechanism that provides tunnel security is
encryption.
There are two common scenarios where VPN is used:
1. LAN-to-LAN connection - Where two internal networks need to be connected together
over the Internet. In this case, each network is protected by an individual NetDefend
Firewall and the VPN tunnel is set up between them.
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