ZyXEL p-2802h-i1 Manual Do Utilizador

Chapter 14 VPN Screens

P-2802H(W)(L)-I Series User’s Guide

Manual key management is useful if you have problems with IKE key management.

An SPI is used to distinguish different SAs terminating at the same destination and using the 
same IPSec protocol. This data allows for the multiplexing of SAs to a single gateway. The 
SPI (Security Parameter Index) along with a destination IP address uniquely identify a 
particular Security Association (SA). The SPI is transmitted from the remote VPN gateway to 
the local VPN gateway. The local VPN gateway then uses the network, encryption and key 
values that the administrator associated with the SPI to establish the tunnel.
Current ZyXEL implementation assumes identical outgoing and incoming SPIs.

Phase 2

Active Protocol 

Use the drop-down list box to choose from ESP or AH. 

Encryption 

Algorithm

This field is available when you select ESP in the Active Protocol field.
Select DES, 3DES, AES or NULL from the drop-down list box. 
When you use one of these encryption algorithms for data communications, both 

the sending device and the receiving device must use 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. This implementation of AES uses 

a 128-bit key. AES is faster than 3DES. 
Select NULL to set up a tunnel without encryption. When you select NULL, you 

do not enter an encryption key.

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 SHA-1 for maximum security. 

SA Life Time 

(Seconds)

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

It may range from 60 to 3,000,000 seconds (almost 35 days). 
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. 

Encapsulation 

Select Tunnel mode or Transport mode from the drop-down list box. 

Perfect Forward 

Secrecy (PFS)

Perfect Forward Secrecy (PFS) is disabled (NONE) by default in phase 2 IPSec 

SA setup. This allows faster IPSec setup, but is not so secure. Choose DH1 or 

DH2 from the drop-down list box 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 (more secure, yet slower). 

Back

Click Back to return to the previous screen.

Apply

Click Apply to save your changes back to the ZyXEL Device and return to the 

VPN-IKE screen.

Cancel

Click Cancel to return to the VPN-IKE screen without saving your changes. 

Table 78   Advanced VPN IKE