Ike Phases - ZyXEL Communications VMG1312-B10C User Manual

• Inside header: The inside IP header contains the destination IP address of the final system
behind the VPN gateway. The security protocol appears after the outer IP header and before the
inside IP header.

19.3.3 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.
• 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.
VMG1312-B10C User's Guide
Chapter 19 VPN
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