K31. Can Zywall Behave As A Nat Router Supporting Ipsec Pass Through And An Ipsec Gateway Simultaneously; Scanned By Anti-Virus, Idp And Anti-Spam Feature In Zywall Zynos V4.0; L01. Basic Cryptography Concept - ZyXEL Communications ZyWall 35 Support Notes

If the VPN connection is initiated from the security gateway outside of ZyWALL, NAT port forwarding
and Firewall forwarding are necessary.
To configure NAT port forwarding, please go to WEB interface, Setup/ "NAT", put the secure gateway's
IP address in default server.
To configure Firewall forwarding, please go to WEB interface, Setup/Firewall, select Packet Direction to
WAN to LAN, and create a firewall rule the forwards IKE(UDP:500).
K31. Can ZyWALL behave as a NAT router supporting IPSec pass through and an IPSec
gateway simultaneously?
No, ZyWALL can't support them simultaneously. You need to choose either one. If ZyWALL is to support
IPSec pass through, you have to disable the VPN function on ZyWALL. To disable it, you can either
deactivate each VPN rule or issue a CI command, "IPSec switch off".
K32. Will the traffic coming in through the VPN tunnel also be scanned by Anti-Virus, IDP
and Anti-Spam feature in ZyWALL ZyNOS v4.0?
No, VPN traffic will not be inspected by be scanned by Anti-Virus, IDP and Anti-Spam module.
However, we manage to support this feature in the forthcoming ZyNOS firmware.
L. PKI FAQ

L01. Basic Cryptography concept

Encryption and decryption are two major operations involved in cryptography. Whenever we would
like to send some secret over an insecure media, such as Internet, we may encrypt the secret before
sending it out. The receiver thus needs the corresponding decryption key to recover the encrypted
secrete. We need to have keys for both encryption and decryption. The key used to encrypt data is
called the encryption key, and the key for decryption is called the decryption key.
Cryptography can be categorized into two types, symmetric and asymmetric cryptography. For
symmetric cryptography, the encryption key is the same with the decryption. Otherwise, we the
cryptography as asymmetric.
Symmetric cryptography, such as DES, 3DES, AES, is normally used for data transmission, since it
requires less computation power than asymmetric cryptography. The task of privately choosing a key
before communicating, however, can be problematic. Applications in real case may use asymmetric
cryptography for to protect distribution of keys (symmetric), and uses symmetric cryptography for
All contents copyright (c) 2006 ZyXEL Communications Corporation.
ZyWALL 35 Support Notes
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