ZyXEL Communications NBG420N Manual Do Utilizador

 Chapter 15 IPSec VPN

NBG420N User’s Guide

Use this screen to configure VPN rules (tunnels) that use manual keys. Manual key 
management is useful if you have problems with IKE key management.
Select Manual in the IPSec Keying Mode field on the Rule Setup screen to open the screen 
as shown in 

You might set up an IPSec SA using manual keys when you want to establish a VPN tunnel 
quickly, for example, for troubleshooting. You should only do this as a temporary solution, 
however, because it is not as secure as a regular IPSec SA.
In IPSec SAs using manual keys, the NBG420N and remote IPSec router do not establish an 
IKE SA. They only establish an IPSec SA. As a result, an IPSec SA using manual keys has 
some characteristics of IKE SA and some characteristics of IPSec SA. There are also some 
differences between IPSec SA using manual keys and other types of SA.

In IPSec SA using manual keys, you can only specify one encryption algorithm and one 
authentication algorithm. There is no DH key exchange, so you have to provide the encryption 
key and the authentication key the NBG420N and remote IPSec router use.

Note: The NBG420N and remote IPSec router must use the same encryption key and 

authentication key.

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.

SA Life Time 

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

field. The minimum value is 180 seconds.
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 

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
PFS changes the root key that is used to generate encryption keys for each 

IPSec SA. It is more secure but takes more time.

Basic...

Click Basic... to go to the previous VPN configuration screen. 

Apply

Click Apply to save the changes. 

Reset

Click Reset to begin configuring this screen afresh.

Cancel

Click Cancel to exit the screen without making any changes.

Table 64   Security > VPN > Rule Setup: IKE (Advanced)  (continued)