ZyXEL Communications P-661H-61, Manual

Page: 233 / 404

Chapter 16 VPN
P-661HNU-Fx User’s Guide
233
16.6.5 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 104 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 which protocol to use (ESP or AH) for the IKE key exchange.
• Choose an encryption algorithm.
• Choose an authentication algorithm
• Choose whether to enable Perfect Forward Secrecy (PFS) using Diffie-Hellman
public-key cryptography – see Appendix D on page 335 . Select None (the
default) to disable PFS.
• Choose Tunnel mode or Transport mode.