ZyXEL 793H Guida Utente

Chapter 11 IPSec VPN

P-793H User’s Guide

Click Security, VPN and Monitor to open the SA Monitor screen as shown. Use this screen 
to display and manage active VPN connections.
When there is outbound traffic but no inbound traffic, the SA times out automatically after two 
minutes. A tunnel with no outbound or inbound traffic is "idle" and does not timeout until the 
SA lifetime period expires. You can also configure the ZyXEL Device to renegotiate an IPSec 
SA when the SA lifetime expires, even if there is no traffic.

Security Protocol

IPSec Protocol 

Select ESP if you want to use ESP (Encapsulation Security Payload). The ESP 

protocol (RFC 2406) provides encryption as well as some of the services offered 

by AH. If you select ESP here, you must select options from the Encryption 

Algorithm and Authentication Algorithm fields (described next).

Encryption 

Algorithm

Select DES, 3DES or NULL from the drop-down list box. 
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. Select NULL to set up a tunnel without encryption. When you select 

NULL, you do not enter an encryption key.

Encryption Key

With DES, type a unique key 8 characters long. With 3DES, type a unique key 24 

characters long. Any characters may be used, including spaces, but trailing 

spaces are truncated.

Authentication 

Algorithm

Select SHA1 or MD5 from the drop-down list box. 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 SHA1 for maximum security. 

Authentication Key

Type a unique authentication key to be used by IPSec if applicable. Enter 16 

characters for MD5 authentication or 20 characters for SHA1 authentication. Any 

characters may be used, including spaces, but trailing spaces are truncated.

Back

Click Back to return to the previous screen.

Apply

Click Apply to save your changes back to the ZyXEL Device.

Reset

Click Reset to begin configuring this screen afresh.

Table 54   VPN > Setup > Edit > Manual (continued)