ZyXEL Communications 2WG - Manual (Page 26)

ZyWALL 2WG Support Notes
All contents copyright (c) 2006 ZyXEL Communications Corporation.
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2. When choosing DHCP setting as a ‘Server’, the LAN will automatically assign IP, subnet,
gateway and DNS to the associated clients.
3. When choosing DHCP setting as a ‘Relay’, the LAN will forward the DHCP request to
another DHCP server.
Using NAT/Multi-NAT
• What is Multi-NAT?
• How NAT works
• NAT Mapping Types
• SUA versus Multi-NAT
• Example
Step 1. Applying NAT on WAN Interface
Step 2. Configuring NAT Address Mapping
Step 3. Using Multiple Global IP addresses for clients and servers (One-to-One, Many-to-One,
Server Set mapping types)
• Application -- Non NAT-Friendly Support
• What is Multi-NAT?
NAT (Network Address Translation-NAT RFC 1631) is the translation of an Internet Protocol address used
within one network to a different IP address known within another network. One network is designated the
inside network and the other is the outside . Typically, a company maps its local inside network addresses to one
or more global outside IP addresses and "unmaps" the global IP addresses on incoming packets back into local
IP addresses. The IP addresses for the NAT can be either fixed or dynamically assigned by the ISP. In addition,
you can designate servers, e.g., a web server and a telnet server, on your local network and make them
accessible to the outside world. If you do not define any servers, NAT offers the additional benefit of firewall
protection. In such case, all incoming connections to your network will be filtered out by the ZyWALL, thus
preventing intruders from probing your network.
The SUA feature that the ZyWALL supports previously operates by mapping the private IP addresses to a
global IP address. It is only one subset of the NAT. The ZyWALL supports the most of the features of the NAT
based on RFC 1631, and we call this feature as 'Multi-NAT'. For more information on IP address translation,
please refer to RFC 1631, The IP Network Address Translator (NAT) .