PassFinder AP2520 VoIP Router/Gateway Operation Manual
Version 1.10 / Mar. 2002
AddPac Technology Co., Ltd.
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4.8.
NAT(Network Address Translation) Configuration
One of problems of the Internet is that available IP address space is decreasing.
The Network Address Translation (NAT) changes uncertified address that is used
in the inside network into another IP address (usually, registered address) when
the address goes outside. Also, when a registered IP address comes to the
inside network from outside, NAT changes it into an internal IP address.
NAT can be useful for the following cases:
z
When the user wants to use Internet but the user cannot have a unique,
certified address. In this case, NAT connects the private IP network that
uses an unregistered IP address with the global Internet.
NAT shall be set in the Gateway that is located in the boarder between the
public network (usually called an outside network) such as the Internet and
the stub domain (usually called an inside network.) Before sending packets
to outside networks, NAT converts internal private IP address into unique IP
addresses.
z
When the manager needs to change inside network address for the
security reason or other reasons. In this case, without changing IP address
that is a lot of work, the manager can translate addresses as using NAT.
z
When the manager needs to distribute TCP traffic for load-sharing. In this
case, the manager can map several local IP addresses into one global IP
address as using the TCP load distribution function. When users access to
the network from outside, they need to use the global IP address to access
to the network and pass through the Gateway. Through the TCP session,
load distribution is possible.
Information
