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This article mainly explains "what are the initialization methods of address translation table in nat". The explanation in this article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the initialization methods of address translation table in nat".

There are three ways to realize NAT, which are: 1) static address translation, which explicitly translates the private address and public network address one to one; 2) dynamic address translation, when the private IP address of the internal network is translated into the public IP address, the IP address is uncertain; 3, the port address translation changes the source port of the outgoing packet and carries on the port translation.

The operating environment of this tutorial: windows7 system, Dell G3 computer.

NAT is a technology that translates internal private addresses into public network addresses.

It is divided into three categories:

1. Static address transfer: one-to-one explicit translation between private address and public network address

2. Dynamic address translation: the NAT converter has a public network address pool, which can dynamically assign an unused public network address to internal private addresses for communication. Form a temporary mapping relationship

3. Port address translation: one port of a public network address corresponds to a private address. Multiple private addresses can correspond to a public network address.

Extended data:

NAT (Network Address Translation, Network address Translation) was proposed in 1994. The NAT method can be used when some hosts within the private network are already assigned local IP addresses (that is, private addresses used only in this private network), but now want to communicate with hosts on the Internet (without encryption).

This method requires the installation of NAT software on a router connected from a private network (private network IP) to the Internet (public network IP). A router with NAT software is called a NAT router, which has at least one valid external global IP address (public network IP address). In this way, when communicating with the outside world, all hosts using local addresses (private IP addresses) have to translate their local addresses into global IP addresses on the NAT router before they can connect with the Internet.

In addition, this way of using a small number of global IP addresses (public network IP addresses) to represent more private IP addresses will help slow the depletion of available IP address space. There is a description of NAT in RFC 2663.

There are three ways to implement NAT, namely, static translation Static Nat, dynamic conversion Dynamic Nat and port multiplexing OverLoad.

Static translation refers to the translation of private IP addresses in the internal network to public IP addresses. IP address pairs are one-to-one and are immutable, and a private IP address is only translated into a public IP address. With the help of static conversion, the external network can access some specific devices (such as servers) in the internal network.

Dynamic translation means that when the private IP address of the internal network is translated into a public IP address, the IP address is uncertain and random, and all private IP addresses authorized to access the Internet can be randomly translated into any specified legal IP address. That is, dynamic translation can occur as long as you specify which internal addresses can be translated and which legal addresses are used as external addresses. Dynamic translation can use multiple sets of legitimate external addresses. When the legal IP address provided by ISP is slightly less than the number of computers within the network. Dynamic conversion can be used.

Port multiplexing (Port address Translation,PAT) refers to changing the source port of outbound packets and performing port translation, namely port address translation (PAT,Port Address Translation). The port multiplexing mode is adopted. All hosts in the internal network can share a legitimate external IP address to access Internet, which can maximize the saving of IP address resources. At the same time, all hosts within the network can be hidden to effectively avoid attacks from internet. Therefore, port multiplexing is the most widely used in the network at present.

ALG (Application Level Gateway), that is, application-level gateway technology: traditional NAT technology only transforms IP layer and transport layer headers, but some application layer protocols contain address information in protocol data packets. In order to enable these applications to transparently complete NAT conversion, NAT uses a technology called ALG, which can also translate the address information contained in these applications when communicating with NAT. For example, PORT/PASV commands of FTP protocol, "A" and "PTR" queries commands of DNS protocol and some ICMP message types all need corresponding ALG to support.

If the protocol data packet does not contain address information, it is easy to use the traditional NAT technology to complete the transparent address translation function. Usually, the following applications we use can directly make use of the traditional NAT technology: HTTP, TELNET, FINGER, NTP, NFS, ARCHIE, RLOGIN, RSH, RCP and so on.

Thank you for your reading, the above is the content of "what are the initialization methods of address translation table in nat". After the study of this article, I believe you have a deeper understanding of what the initialization mode of address translation table in nat has, and the specific use still needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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