ZyXEL SBG3300-N000 User Guide - Page 291

Chapter 20 IPSec VPN 20.7.3 IKE Phases There are two phases to every IKE (Internet Key Exchange) negotiation - phase 1 (Authentication) and phase 2 (Key Exchange). A phase 1 exchange establishes an IKE SA and the second one uses that SA to negotiate SAs for IPSec. Figure 124 Two Phases to Set Up the IPSec SA In phase 1 you must: • Choose a negotiation mode. • Authenticate the connection by entering a pre-shared key. • Choose an encryption algorithm. • Choose an authentication algorithm. • Choose a Diffie-Hellman public-key cryptography key group (DH1 or DH2). • Set the IKE SA lifetime. This field allows you to determine how long an IKE SA should stay up before it times out. An IKE SA times out when the IKE SA lifetime period expires. If an IKE SA times out when an IPSec SA is already established, the IPSec SA stays connected. In phase 2 you must: • Choose an encryption algorithm. • Choose an authentication algorithm • Choose a Diffie-Hellman public-key cryptography key group. • Set the IPSec SA lifetime. This field allows you to determine how long the IPSec SA should stay up before it times out. The Device automatically renegotiates the IPSec SA if there is traffic when the IPSec SA lifetime period expires. If an IPSec SA times out, then the IPSec router must renegotiate the SA the next time someone attempts to send traffic. 20.7.4 Negotiation Mode The phase 1 Negotiation Mode you select determines how the Security Association (SA) will be established for each connection through IKE negotiations. SBG3300-N Series User's Guide 291