ZyXEL 802.11g Bedienungsanleitung PDF herunterladen (Seite 253)

P-662H/HW-D Series User’s Guide

Chapter 16 VPN Screens 253

• 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 16.12.3 on page 254. 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 ZyXEL Device automatically renegotiates the

IPSec SA if there is traffic when the IPSec SA lifetime period expires. The ZyXEL

Device 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.

16.12.1 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

number). This mode features identity protection (your identity is not revealed in the

negotiation).

• Aggressive Mode is quicker than Main Mode because it eliminates several steps when

the communicating parties are negotiating authentication (phase 1). However the trade-

off is that faster speed limits its negotiating power and it also does not provide identity

protection. It is useful in remote access situations where the address of the initiator is not

know by the responder and both parties want to use pre-shared key authentication.

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ZyXEL 802.11g Bedienungsanleitung Seite 253