ZyXEL Communications ZyWALL 1000 User Manual

Chapter 4 Wizard Setup

ZyWALL USG 1000 User’s Guide

Phase 2 in an IKE uses the SA that was established in phase 1 to negotiate SAs for IPSec.

Figure 40   VPN Advanced Wizard: Step 4 

The following table describes the labels in this screen.

Table 20   VPN Advanced Wizard: Step 4

Phase 2 Setting

Active Protocol

Select the security protocols used for an SA. 
Both AH and ESP increase ZyWALL processing requirements and 

communications latency (delay).

Encapsulation

Tunnel is compatible with NAT, Transport is not.
Tunnel mode encapsulates the entire IP packet to transmit it securely. Tunnel 

mode is required for gateway services to provide access to internal systems. 

Tunnel mode is fundamentally an IP tunnel with authentication and encryption. 

Transport mode is used to protect upper layer protocols and only affects the 

data in the IP packet. In Transport mode, the IP packet contains the security 

protocol (AH or ESP) located after the original IP header and options, but before 

any upper layer protocols contained in the packet (such as TCP and UDP). 

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.  AES128 uses a 128-bit key and is faster than 3DES. AES192 uses 

a 192-bit key and AES256 uses a 256-bit key. Select Null to have no 

encryption.