ZyXEL Communications Internet Security Gateway ZyWALL 100, User Manual

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ZyWALL Series Internet Security Gateway
VPN Screens 15-23
Table 15-8 VPN IKE: Advanced
LABEL DESCRIPTION
Enable Replay
Detection As a VPN setup is processing intensive, the system is vulnerable to Denial of Service
(DoS) attacks The IPSec receiver can detect and reject old or duplicate packets to
protect against replay attacks. Select
YES from the drop-down menu to enable replay
detection, or select NO to disable it.
Local Port Start "0" is the default and signifies any port. Type a port number from 0 to 65535. Some
of the most common IP ports are: 21, FTP; 53, DNS; 23, Telnet; 80, HTTP; 25,
SMTP; 110, POP3.
Local Port End Type a port number in this field to define a port range. This port number must be
greater than that specified in the previous field. If
Local Port Start is left at 0, Local
Port End will also remain at 0.
Remote Port Start Type up to 32 characters to identify this VPN policy. You may use any character,
including spaces, but the ZyWALL drops trailing spaces.
Remote Port End Enter a port number in this field to define a port range. This port number must be
greater than that specified in the previous field. If
Remote Port Start is left at 0,
Remote Port End will also remain at 0.
Phase 1
Negotiation Mode Select Main or Aggressive from the drop-down list box. Multiple SAs connecting
through a secure gateway must have the same negotiation mode.
Encryption
Algorithm
Select DES , 3DES or AES from the drop-down list box.
The ZyWALL and the remote IPSec router generate an encryption key from the
Diffie-Hellman key exchange. 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. AES uses a 128-bit key. AES is faster than 3DES
and provides a similar level of security.
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.