Using Nat / Multi-Nat - ZyXEL Communications P-2608HWL-D1 Support Notes

Using NAT / Multi-NAT

•
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. Inside and outside networks are
networks relative to the Prestige. The network connected behind the Prestige is the "inside network＂ while
the remote network (such as the Internet) is the "outside network＂. When a packet is received from the
inside hosts, NAT maps and changes the source IP address of the received packets to one or more IP addresses
known to the outside network. When a packet is received from the outside network, NAT unmaps and changes
the outside source IP address back to the local IP address known to the inside network. The Prestige WAN IP
address for NAT can be static (fixed) or dynamically assigned by the ISP. In addition, you can also make one or
more servers on the inside network visible/accessible to the outside network. If no specified inside server is
defined, NAT provides an added layer of security to filter traffic to the Prestige and prevent network
probing/port scanning.
With SUA (Single User Account) supports, the Prestige maps the private (local) IP addresses to one global
(WAN) IP address. This means you can only have one NAT behind the Prestige. To allow more than one NATs
behind the Prestige, RFC 1631,
for the Prestige. This feature is also known as Multi-NAT. For more information, refer to RFC 1631.
•
How NAT works
Internal Local Addresses (ILA) refer to the local or private IP addresses known to the local network and Inside
Global Address (IGA) refers to the public or global IP address known to the outside network. The following
figure shows a network example. NAT operates by mapping the ILA to the IGA required for communication
with hosts on other networks. That means NAT replaces the original source IP address in the packets with the
global IP address. To the outside network, this makes the packets look as if they originate from the Prestige and
not from the inside computers. The Prestige keeps a record of the ILA-IGA mappings so packets received from
the outside network can be forwarded to the intended computer on the inside network.
All contents copyright (c) 2005 ZyXEL Communications Corporation.
P-2608HWL Series Support Notes
The IP Network Address Translator (NAT)
is implemented in ZyNOS V3.40
21