ZyXEL 2WG Guida Utente

Chapter 3 Wizard Setup

ZyWALL 2WG User’s Guide

Figure 30   VPN Wizard: IKE Tunnel Setting

The following table describes the labels in this screen.

Table 18   VPN Wizard: IKE Tunnel Setting

Negotiation Mode

Select Main Mode for identity protection. Select Aggressive Mode to allow 

more incoming connections from dynamic IP addresses to use separate 

passwords. 

Note: Multiple SAs (security associations) connecting through a 

secure gateway must have the same negotiation mode.

Encryption 

Algorithm

When DES is used for data communications, both sender and receiver must 

know the same secret key, which can be used to encrypt and decrypt the 

message or to generate and verify a message authentication code. The DES 

encryption algorithm uses a 56-bit key. Triple DES (3DES) is a variation on DES 

that uses a 168-bit key. As a result, 3DES is more secure than DES. It also 

requires more processing power, resulting in increased latency and decreased 

throughput.  This implementation of AES uses a 128-bit key. AES is faster than 

3DES.

Authentication 

Algorithm

MD5 (Message Digest 5) and SHA1 (Secure Hash Algorithm) are hash 

algorithms used to authenticate packet data. The SHA1 algorithm is generally 

considered stronger than MD5, but is slower. Select MD5 for minimal security 

and SHA-1 for maximum security. 

Key Group

You must choose a key group for phase 1 IKE setup. DH1 (default) refers to 

Diffie-Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman 

Group 2 a 1024 bit (1Kb) random number. DH5 refers to Diffie-Hellman Group 5 

a 1536-bit random number.

SA Life Time 

(Seconds)

Define the length of time before an IKE SA automatically renegotiates in this 

field. The minimum value is 180 seconds. 
A short SA Life Time increases security by forcing the two VPN gateways to 

update the encryption and authentication keys. However, every time the VPN 

tunnel renegotiates, all users accessing remote resources are temporarily 

disconnected.