ZyXEL Communications ZyWALL 1000 User Manual

Chapter 20 IPSec VPN

ZyWALL USG 1000 User’s Guide

Encapsulation 

Mode

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. You should only select this if the 

IPSec SA is used for communication between the ZyWALL and remote IPSec 

router.
If you select Transport mode, the ZyWALL automatically switches to Tunnel 

mode if the IPSec SA is not used for communication between the ZyWALL and 

remote IPSec router. In this case, the ZyWALL generates a log message for this 

change.

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.

Encryption 

Algorithm

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 algorithms and 

keys. Longer keys require more processing power, resulting in increased latency 

and decreased throughput.

Authentication 

Algorithm

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.

Encryption 

Key

This field is applicable when you select an Encryption Algorithm. Enter the 

encryption key, which depends on the encryption algorithm.
DES - type a unique key 8-32 characters long
3DES - type a unique key 24-32 characters long
AES128 - type a unique key 16-32 characters long
AES192 - type a unique key 24-32 characters long
AES256 - type a unique key 32 characters long
You can use any alphanumeric characters or ,;|`~!@#$%^&*()_+\{}':./<>=-".
If you want to enter the key in hexadecimal, type “0x” at the beginning of the key. 

For example, "0x0123456789ABCDEF" is in hexadecimal format; in 

“0123456789ABCDEF” is in ASCII format. If you use hexadecimal, you must enter 

twice as many characters as listed above.
The remote IPSec router must have the same encryption key.
The ZyWALL ignores any characters above the minimum number of characters 

required by the algorithm. For example, if you enter 

1234567890XYZ

 for a DES 

encryption key, the ZyWALL only uses 

12345678

. The ZyWALL still stores the 

longer key.

Table 92   VPN > IPSec VPN > VPN Connection > Manual Key > Edit (continued)