ZyXEL ZyWALL USG 2000 User Guide - Page 470

Chapter 25 IPSec VPN IKE SA Overview The IKE SA provides a secure connection between the ZyWALL and remote IPSec router. It takes several steps to establish an IKE SA. The negotiation mode determines how many. There are two negotiation modes--main mode and aggressive mode. Main mode provides better security, while aggressive mode is faster. Note: Both routers must use the same negotiation mode. These modes are discussed in more detail in Negotiation Mode on page 474. Main mode is used in various examples in the rest of this section. IP Addresses of the ZyWALL and Remote IPSec Router To set up an IKE SA, you have to specify the IP addresses of the ZyWALL and remote IPSec router. You can usually enter a static IP address or a domain name for either or both IP addresses. Sometimes, your ZyWALL might offer another alternative, such as using the IP address of a port or interface, as well. You can also specify the IP address of the remote IPSec router as 0.0.0.0. This means that the remote IPSec router can have any IP address. In this case, only the remote IPSec router can initiate an IKE SA because the ZyWALL does not know the IP address of the remote IPSec router. This is often used for telecommuters. IKE SA Proposal The IKE SA proposal is used to identify the encryption algorithm, authentication algorithm, and Diffie-Hellman (DH) key group that the ZyWALL and remote IPSec router use in the IKE SA. In main mode, this is done in steps 1 and 2, as illustrated next. Figure 337 IKE SA: Main Negotiation Mode, Steps 1 - 2: IKE SA Proposal One or more proposals, each one consisting of: - encryption algorithm - authentication algorithm - Diffie-Hellman key group 1 X 470 2 Y ZyWALL USG 2000 User's Guide