ZyXEL Communications 200 Series - Manual (Page 102)

Chapter 4 Wizard Setup
ZyWALL USG 100/200 Series User’s Guide
102
The following table describes the labels in this screen.
4.8.6 VPN Advanced Wizard - Phase 1
Phases: IKE (Internet Key Exchange) negotiation has two phases. A phase 1 exchange
establishes an IKE SA (Security Association) and phase 2 (Key Exchange) uses the SA to
negotiate SAs for IPSec.
Table 19 VPN Advanced Wizard: Step 3
LABEL DESCRIPTION
Negotiation Mode Select Main for identity protection. Select Aggressive to allow more incoming
connections from dynamic IP addresses to use separate passwords.
Note: Multiple SAs (security associations) connecting through a
secure gateway must have the same negotiation mode.
Encryption
Algorithm When DES is used for data communications, both sender and receiver must
know 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. AES128 uses a 128-bit key and is faster than 3DES. AES192 uses
a 192-bit key and AES256 uses a 256-bit key. Select Null to have no
encryption.
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 slower. Select MD5 for minimal security
and SHA1 for maximum security.
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. DH5 refers to Diffie-Hellman Group 5
a 1536 bit random number.
SA Life Time
(Seconds) Define the length of time before an IKE 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.
NAT Traversal Select this check box to enable NAT traversal. NAT traversal allows you to set
up a VPN connection when there are NAT routers between the two IPSec
routers.
Note: The remote IPSec router must also have NAT traversal
enabled. See VPN, NAT, and NAT Traversal on page 377
for more information.
Dead Peer
Detection (DPD) Select this check box if you want the ZyWALL to make sure the remote IPSec
router is there before it transmits data through the IKE SA. If there has been no
traffic for at least 15 seconds, the ZyWALL sends a message to the remote
IPSec server. If the remote IPSec server responds, the ZyWALL transmits the
data. If the remote IPSec server does not respond, the ZyWALL shuts down the
IKE SA.
Next Click Next to continue.