Chapter 4 Wizard Setup

The following table describes the labels in this screen.

Table 20 VPN Advanced Wizard: Step 4

LABEL

DESCRIPTION

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.

 

 

SA Life Time

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

 

field.

 

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.

 

 

Perfect Forward

Perfect Forward Secret (PFS) is disabled (None) by default in phase 2 IPSec

Secret (PFS)

SA setup. This allows faster IPSec setup, but is not so secure.

 

Select DH1, DH2 or DH5 to enable PFS. DH1 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 (more secure, yet slower).

 

 

Policy Setting

 

 

 

Local Policy (IP/

Type a static local IP address that corresponds to the remote IPSec router's

Mask)

configured remote IP address.

 

To specify IP addresses on a network by their subnet mask, type the subnet

 

mask of the LAN behind your ZyWALL.

 

 

Incoming Interface

Select an interface from the drop-down list box to have packets encrypted by

 

the remote IPSec router to enter the ZyWALL via this interface.

 

 

Remote Policy (IP/

Type a static local IP address that corresponds to the remote IPSec router's

Mask)

configured local IP address.

 

To specify IP addresses on a network by their subnet mask, type the subnet

 

mask of the LAN behind the remote gateway.

 

 

Property

 

 

 

Nailed-Up

Select this if you want the ZyWALL to automatically renegotiate the IPSec SA

 

when the SA life time expires.

 

 

Next

Click Next to continue.

 

 

104

 

ZyWALL USG 100/200 Series User’s Guide