Prestige 2602HW Series User’s Guide

 

Table 66 VPN IKE: Advanced Setup (continued)

 

 

 

 

LABEL

DESCRIPTION

 

 

 

 

Encryption

This field is available when you select ESP in the Active Protocol field.

 

Algorithm

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

Select SHA1 or MD5 from the drop-down list box. MD5 (Message Digest 5) and

 

Algorithm

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-1for maximum security.

 

SA Life Time

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

 

(Seconds)

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

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

 

Secrecy (PFS)

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).

 

Apply

Click Apply to save your changes back to the Prestige and return to the VPN-IKE

 

 

screen.

 

Cancel

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

 

 

 

17.14 Manual Key Setup

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

17.14.1 Security Parameter Index (SPI)

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.

Chapter 17 VPN Screens

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