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I S P  G L O S S A R Y
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NAT
Last modified: Wednesday, February 01, 2006 

Short for Network Address Translation, an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. A NAT box located where the LAN meets the Internet makes all necessary IP address translations.

NAT serves three main purposes:

  • Provides a type of firewall by hiding internal IP addresses
  • Enables a company to use more internal IP addresses. Since they're used internally only, there's no possibility of conflict with IP addresses used by other companies and organizations.
  • Allows a company to combine multiple ISDN connections into a single Internet connection.
  • Also see dynamic NAT and static NAT.

      Related Links

    Configure NAT for Windows Media Services 9
    This article discusses the firewall ports that you must open to stream content from a media server that is located behind a firewall.

    How Network Address Translation Works
    NAT is like the receptionist in a large office. Let's say you have left instructions with the receptionist not to forward any calls to you unless you request it. Later on, you call a potential client and leave a message for that client to call you back. You tell the receptionist that you are expecting a call from this client and to put her through.

    IP Security and NAT: Oil and Water?
    Despite popular wisdom, IPsec and NAT can be employed together—in some configurations. ISP-Planet explores what you can do and what you can't, and the limitations inherent in today's solutions.

    ISP-Planet: Slipping IPsec Past NAT
    NAT and NAPT are techniques used to share and hide private IP addresses on edge devices like routers and firewalls. Unfortunately, when an IPsec session runs through NAT or NAPT, security is often compromised.

    Network Address Translation Commands
    Cisco Documents: This chapter describes the function and displays the syntax for Network Address Translation (NAT) commands.

    RFC 1631
    Request for Comments document for the IP Network Address Translator (NAT).

    RFC 3022
    Basic Network Address Translation or Basic NAT is a method by which IP addresses are mapped from one group to another, transparent to end users.

    RFC 4008
    This memo defines a portion of the Management Information Base (MIB) for devices implementing NAT function. This MIB module may be used for configuration and monitoring of a device capable of NAT function.

    Related Categories

    Internet Protocols

    Security

    Related Terms

    dynamic NAT

    firewall

    ICS

    Internet

    IP address

    LAN

    MP

    stateful inspection

    static NAT

    traffic