ZyXEL nbg-5715 Guia Do Utilizador

Chapter 18 IPSec VPN

NBG5715 User’s Guide

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.

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 NBG5715 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.

The phase 1 Negotiation Mode you select determines how the Security Association (SA) will be 
established for each connection through IKE negotiations.