Network Address Translation
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OmniAccess 5740 Unified Services Gateway CLI Configuration Guide
Alcatel-Lucent
NAT OVERVIEW
Scarcity of registered IP addresses and related address management issues in
connecting a private network to the Internet created a need for a mechanism such
as NAT.
NAT mechanism translates un-registered "private" IP addresses used in an
internal network to a real "registered" IP on external networks such as the
Internet. When using NAT, only a single unique IP address is required to represent
an entire group of computers.
By configuring NAT on the network gateway, home users and small businesses
can connect their network to the Internet inexpensively and efficiently. As a fringe
benefit, NAT automatically hides internal IP addresses and hence offers
protection from exposing hosts on the private network to the Internet.
Refer the following section for more details on NAT:
• “Types of NAT”
• “Benefits of NAT”
• “Before You Configure NAT”
• “Alcatel-Lucent Specific Overview”
TYPES OF NAT
This section describes following types of NAT:
• “Network Address Port Translation”
• “Static NAT”
• “Dynamic NAT”
N
ETWORK ADDRESS PORT TRANSLATION
Network Address Port Translation (NAPT) is an extension to the basic NAT. In
this, many network addresses and their TCP/UDP ports are translated to a single
network address and its TCP/UDP ports. This involves mapping ports for requests
within a network to an external address via a Public IP to free ports. This helps in
uniquely identifying incoming replies on those connections to specific systems
within the network.
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