Network Address Translation Nat

I. Network Address Translation NAT:

Some hosts in the private network have already been assigned a local IP address, but now they want to communicate with hosts on the Internet. The simplest way is to apply for some global IP addresses, however, there are not many IPv4 addresses in the world, so network address translation is used.

Install Nat software on a vro connected to the Internet by using a private network. The vro with Nat software is called a NAT router. It must have at least one valid external global IP address to connect to the Internet. When a host that uses a local address communicates with the Internet, the local address on the NAT router must be converted to a global IP address. In this way, a large number of hosts in the private network can use the limited number of global IP addresses of NAT routers in turn.

You can use NAT to connect an Intranet to the Internet.

(1) Work at the network layer and Transport Layer

(2) perform address translation on the received packets before forwarding

(3) The Nat network address is bidirectional.

Ii. How Nat routers work (host a communicates with host B)

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When a NAT router has n IP addresses, a maximum of n hosts in the private network can access the Internet.

The host of the private network cannot be used as a server (assuming that hosts on the internet need to initiate communications, when the IP datagram reaches the NAT router, the Nat Router does not know the IP address of the local host to which the destination IP address is to be converted ).

4. Nat router operation process

(1) The intranet computer submits an Internet access request to the NAT router.

(2) The Nat Router performs address translation on the Request Packet

(3) The Nat router submits the conversion request to the internet server.

(4) The Nat router maps to the conversion table.

(5) The Internet server returns a response packet to the NAT router.

(6) Querying the translation table of a NAT router to obtain the ing information

(7) Nat router translation response packet

(8) after the NAT router is converted, it should be packaged and returned to the Intranet computer.

5. Benefits of using NAT to connect the Intranet to the Internet

(1) A common IP address and network connection allow an intranet shared public IP address to access the Internet

(2) protect network security. By hiding the Intranet IP address, hackers cannot directly attack the Intranet.

Vi. Working Principle of Proxy Server

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Network Address Translation Nat