ZyXEL Communications ZYWALL 1050 - V2.00 EDITION 1 Betriebsanweisung PDF herunterladen (Seite 135)

ZyWALL (ZLD) CLI Reference Guide

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CHAPTER 16

IPSec VPN

This chapter explains how to set up and maintain IPSec VPNs in the ZyWALL.

16.1 IPSec VPN Overview

A virtual private network (VPN) provides secure communications between sites without the

expense of leased site-to-site lines. A secure VPN is a combination of tunneling, encryption,

authentication, access control and auditing. It is used to transport traffic over the Internet or

any insecure network that uses TCP/IP for communication.

Internet Protocol Security (IPSec) is a standards-based VPN that offers flexible solutions for

secure data communications across a public network like the Internet. IPSec is built around a

number of standardized cryptographic techniques to provide confidentiality, data integrity and

authentication at the IP layer.

The following figure is one example of a VPN tunnel.

Figure 19 VPN: Example

The VPN tunnel connects the ZyWALL (X) and the remote IPSec router (Y). These routers

then connect the local network (A) and remote network (B).

A VPN tunnel is usually established in two phases. Each phase establishes a security

association (SA), a contract indicating what security parameters the ZyWALL and the remote

IPSec router will use. The first phase establishes an Internet Key Exchange (IKE) SA between

the ZyWALL and remote IPSec router. The second phase uses the IKE SA to securely

establish an IPSec SA through which the ZyWALL and remote IPSec router can send data

between computers on the local network and remote network. This is illustrated in the

following figure.

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ZyXEL Communications ZYWALL 1050 - V2.00 EDITION 1 Betriebsanweisung Seite 135