ZyXEL Communications Prestige 662HW Series, User Manual

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Prestige 662HW Series User’s Guide
VPN Screens 16-13
Figure 16-6 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
section 16.11.3 . Select None (the default) to disable PFS.
Choose Tunnel mode or Transport mode.
Set the IPSec SA lifetime. This field allows you to determine how long the IPSec SA
should stay up before it times out. The Prestige automatically renegotiates the IPSec SA if
there is traffic when the IPSec SA lifetime period expires. The Prestige also automatically
renegotiates the IPSec SA if both IPSec routers have keep alive enabled, even if there is
no traffic. If an IPSec SA times out, then the IPSec router must renegotiate the SA the
next time someone attempts to send traffic.
16.11.1 Negotiation Mode
The phase 1 Negotiation Mode you select determines how the Security Association (SA) will be
established for each connection through IKE negotiations.
Main Mode ensures the highest level of security when the communicating parties are
negotiating authentication (phase 1). It uses 6 messages in three round trips: SA
negotiation, Diffie-Hellman exchange and an exchange of nonces (a nonce is a random