Chapter 25 IPSec VPN

•Use the VPN Gateway screens (see Section 25.2.1 on page 446) to manage the ZyWALL’s VPN gateways. A VPN gateway specifies the IPSec routers at either end of a VPN tunnel and the IKE SA settings (phase 1 settings). You can also activate and deactivate each VPN gateway.

•Use the VPN Concentrator screens (see Section 25.4 on page 465) to combine several IPSec VPN connections into a single secure network.

25.1.2What You Need to Know

An IPSec 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.

Figure 327 VPN: IKE SA and IPSec SA

In this example, a computer in network A is exchanging data with a computer in network B. Inside networks A and B, the data is transmitted the same way data is normally transmitted in the networks. Between routers X and Y, the data is protected by tunneling, encryption, authentication, and other security features of the IPSec SA. The IPSec SA is secure because routers X and Y established the IKE SA first.

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ZyWALL USG 2000 User’s Guide