NAT (Network Address translation)

I. Overview

The English full name of NAT is "network address translation", which is an IETF (Internet Engineering Task Force, Internet Engineering Tasks Group) standard that allows a

The overall organization appears on the Internet with a public IP (Internet Protocol) address. As the name implies, it is a technology that translates the internal private network address (IP address) into a legitimate network IP address. NAT can make that

Connections to the Internet or other IP networks using the private address of the internal network. When a NAT router sends a packet of an internal network to a public network, the IP packet's header translates the private address into a legitimate IP address.

Ii. advantages and disadvantages of NAT

• Advantages

Save Legal registered Address

Increased flexibility for connecting to the Internet

Improved security

• Disadvantages

Increased switching latency

Cause end-to-end IP tracing is not possible

Iii. conversion type of NAT

• Static NAT

Local and global addresses are mapped to one-to-two, and when using static NAT, you must provide an Internet address for each host on the network.

• Dynamic NAT

Allows you to map unregistered IP addresses to addresses in the registered IP address pool, many-to-many.

• PAT

Use the source port to map multiple non-registered IP addresses to a registered IP address (many-to-one), which is also called Port address mapping.

Iv. Principle of operation

The NAT device maintains a status table that maps illegal IP addresses to legitimate IP addresses. Each packet is translated into the correct IP address in the NAT device, which is sent down one level, which means a burden on the processor.

But for the general network, the burden is negligible. In routers running NAT, NAT can convert the IP address of the packet and the port number of the TCP/UDP packet when the packet is delivered. Routers that set NAT functionality

There must be at least one inside (internal) port and one outside (external) port. Internal ports are connected to the intranet, and the external ports are generally connected to the Internet. When IP packets leave the internal network, NAT is responsible for the intranet IP source address

(usually a private address) to a legitimate public IP address. When the IP packet enters the intranet, Nat translates the legitimate public IP destination address into the IP source address of the intranet.

NAT (Network Address translation)