ZyXEL Communications ZyXEL ZyWALL 35 - Manual (Page 570)

ZyWALL 35 User’s Guide
568 Chapter 44 VPN/IPSec Setup
The following table describes the fields in this screen.
Table 209 Menu 27.1.1.1: IKE Setup
FIELD DESCRIPTION
Phase 1
Negotiation
Mode
Press [SPACE BAR] to choose from Main or Aggressive and then press [ENTER].
See earlier for a discussion of these modes. Multiple SAs connecting through a secure
gateway must have the same negotiation mode.
Authentication
Method
Select Pre-Shared Key to use a pre-shared key to identify the ZyWALL and the
remote IPSec router. A pre-shared key identifies a communicating party during a
phase 1 IKE negotiation. It is called "pre-shared" because you have to share it with
another party before you can communicate with them over a secure connection.
Select Certificate to identify the ZyWALL and the remote IPSec router by certificates.
PSK ZyWALL gateways authenticate an IKE VPN session by matching pre-shared keys.
Pre-shared keys are best for small networks with fewer than ten nodes. Enter your
pre-shared key here. Enter up to 31 characters. Any character may be used, including
spaces, but trailing spaces are truncated.
Both ends of the VPN tunnel must use the same pre-shared key. You will receive a
“PYLD_MALFORMED” (payload malformed) packet if the same pre-shared key is not
used on both ends.
Certificate Press [SPACE BAR] to choose the certificate to use for this VPN tunnel. You must
have certificates already configured in the My Certificates web configurator screen
Encryption
Algorithm
The ZyWALL and the remote IPSec router generate an encryption key from the Diffie-
Hellman key exchange. ZyWALL 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 slightly
increased latency and decreased throughput.
This implementation of AES uses a 128-bit key. AES is faster than 3DES.
Press [SPACE BAR] to choose from DES, 3DES or AES and then press [ENTER].
Authentication
Algorithm
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 slightly slower.
Press [SPACE BAR] to choose from SHA1 or MD5 and then press [ENTER].
SA Life Time
(Seconds)
Define the length of time before an IKE Security Association automatically
renegotiates in this field. It may range from 180 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.
Key Group You must choose a key group for phase 1 IKE setup. DH1 (default) refers to Diffie-
Hellman Group 1 a 768 bit random number. DH2 refers to Diffie-Hellman Group 2 a
1024 bit (1Kb) random number.
Phase 2
Active Protocol Press [SPACE BAR] to choose from ESP or AH and then press [ENTER]. See earlier
for a discussion of these protocols.
Encryption
Algorithm
Press [SPACE BAR] to choose from NULL, DES, 3DES or AES and then press
[ENTER]. Select NULL to set up a tunnel without encryption.
Authentication
Algorithm
Press [SPACE BAR] to choose from SHA1 or MD5 and then press [ENTER].
SA Life Time
(Seconds)
Define the length of time before an IPSec Security Association automatically
renegotiates in this field. It may range from 180 to 3,000,000 seconds (almost 35
days).