ZyXEL Communications ZyWALL 300 User Manual

Chapter 20 IPSec VPN

ZyWALL USG 300 User’s Guide

Active Protocol

Select which protocol you want to use in the IPSec SA. Choices are:
AH (RFC 2402) - provides integrity, authentication, sequence integrity (replay 
resistance), and non-repudiation but not encryption. If you select AH, you must 
select an Authentication algorithm.
ESP (RFC 2406) - provides encryption and the same services offered by AH, 
but its authentication is weaker. If you select ESP, you must select an 
Encryption algorithm and Authentication algorithm.
Both AH and ESP increase processing requirements and latency (delay).

Encapsulation

Select which type of encapsulation the IPSec SA uses. Choices are
Tunnel - this mode encrypts the IP header information and the data
Transport - this mode only encrypts the data

Proposal

#

This field is a sequential value, and it is not associated with a specific proposal. 
The sequence of proposals should not affect performance significantly.

Encryption

This field is applicable when the Active Protocol is ESP. Select which key size 
and encryption algorithm to use in the IPSec SA. Choices are:
NULL - no encryption key or algorithm
DES - a 56-bit key with the DES encryption algorithm
3DES - a 168-bit key with the DES encryption algorithm
AES128 - a 128-bit key with the AES encryption algorithm
AES192 - a 192-bit key with the AES encryption algorithm
AES256 - a 256-bit key with the AES encryption algorithm
The ZyWALL and the remote IPSec router must use the same key. Longer keys 
require more processing power, resulting in increased latency and decreased 
throughput.

Authentication

Select which hash algorithm to use to authenticate packet data in the IPSec SA. 
Choices are SHA1 and MD5. SHA1 is generally considered stronger than MD5, 
but it is also slower.

Add icon

This column contains icons to add and remove proposals.
To add a proposal, click the Add icon at the top of the column.
To remove a proposal, click the Remove icon next to the proposal. The 
ZyWALL confirms that you want to delete it before doing so.

SA Life Time 
(Seconds)

Type the maximum number of seconds the IPSec SA can last. Shorter life times 
provide better security. The ZyWALL automatically negotiates a new IPSec SA 
before the current one expires, if there are users who are accessing remote 
resources.

Perfect Forward 
Secrecy (PFS)

Select whether or not you want to enable Perfect Forward Secrecy (PFS) and, if 
you do, which Diffie-Hellman key group to use for encryption. Choices are:
none - disable PFS
DH1 - enable PFS and use a 768-bit random number
DH2 - enable PFS and use a 1024-bit random number
DH5 - enable PFS and use a 1536-bit random number
PFS changes the root key that is used to generate encryption keys for each 
IPSec SA. It is more secure but takes more time.

Policy

Table 91   VPN > IPSec VPN > VPN Connection > Edit (continued)