ZyXEL Communications Corporation VMG1312B10C Manuel D’Utilisation

 Chapter 19 VPN

VMG1312-B10C User’s Guide

Pre-Shared Key

Type your pre-shared key in this field. A pre-shared key identifies a communicating 
party during a phase 1 IKE negotiation. 

Type from 8 to 31 case-sensitive ASCII characters or from 16 to 62 hexadecimal ("0-9", 
"A-F") characters. You must precede a hexadecimal key with a "0x” (zero x), which is 
not counted as part of the 16 to 62 character range for the key. For example, in 
"0x0123456789ABCDEF", “0x” denotes that the key is hexadecimal and 
“0123456789ABCDEF” is the key itself.

Certificates

If you use a certificate for authentication, select the certificates to use from the lists. 
You can import certificates in the Security > Certificates screens.

Perfect Forward 

Secrecy (PFS)

Select whether or not you want to enable Perfect Forward Secrecy (PFS)

PFS changes the root key that is used to generate encryption keys for each IPSec SA. 
The longer the key, the more secure the encryption, but also the longer it takes to 
encrypt and decrypt information. Both routers must use the same DH key group. 
Choices are:

Diffie-Hellman Group2 - use a 1024-bit random number

Diffie-Hellman Group5 - use a 1536-bit random number

Diffie-Hellman Group14 - use a 2048-bit random number

Show Advanced 

Settings

Click this to display advanced settings.

Advanced Setting - Phase 1

Mode

Select the negotiation mode to use to negotiate the IKE SA. Choices are:

Main - this encrypts the Device’s and remote IPSec router’s identities but takes more 
time to establish the IKE SA.

Aggressive - this is faster but does not encrypt the identities.

The Device and the remote IPSec router must use the same negotiation mode.

Encryption 

Algorithm

Select which key size and encryption algorithm to use in the IKE SA. Choices are:

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

AES196 - a 196-bit key with the AES encryption algorithm

AES256 - a 256-bit key with the AES encryption algorithm

The Device and the remote IPSec router must use the same key size and encryption 
algorithm. Longer keys require more processing power, resulting in increased latency 
and decreased throughput.

Integrity 

Algorithm

Select which hash algorithm to use to authenticate packet data. Choices are MD5, 
SHA1, SHA2-256 and SHA2-512. SHA is generally considered stronger than MD5, 
but it is also slower.

Diffie-Hellman 

Group for Key 

Exchange 

Select which Diffie-Hellman key group you want to use for encryption keys. Choices for 
number of bits in the random number are: 768, 1024, 2048, 3072, 4096, 6144, 8192.

The longer the key, the more secure the encryption, but also the longer it takes to 
encrypt and decrypt information. Both routers must use the same DH key group.

Key Life Time

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

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. 

IPSec VPN: Add