Nat and Napt

Often hear the concept of internal IP and external IP, then what is the meaning of these two concepts.

As we all know, with the proliferation of Internet users, IPv4 's address is becoming more and more inadequate, so how to solve this problem, in order to alleviate the pressure of IPv4 address, people put forward NAT and NAPT solutions, to some extent, to alleviate the IPV4 address is not enough to bring the pressure.

NAT: "Network address translation".

1> concept

Generally speaking, the internal IP address is used in institutions and enterprises, and is generally 192.168.1.1~192.168.1.254. Then, when users want to communicate with the outside world, they need to use the external IP address provided by the ISP, which is the only address that is identified by a specialized organization.

NAT is a protocol that converts an internal IP address into an external IP address. When internal nodes to communicate with the external network, at the gateway, the internal IP address to replace the external IP address, so that the normal use of the Internet, NAT can enable multiple computers to share the Internet connection, this function is a good solution to the problem of public IP address shortage.

2> classification

Static NAP technology: The private IP address and external IP address of the internal network correspond to one by one, and a private IP address is converted to a public IP address only. With static transformations, you can implement an external network's access to certain devices in the internal network, such as servers.

Dynamic NAP technology: When the private IP address of the internal network is converted to an external IP address, the external IP address is randomly assigned to the internal private IP address.

NAPT: "Network address port conversion".

Mapping an internal IP address to a different port on an IP address of an external network is the conversion of the internal address + internal Port number to the external address + external port number, which enables many users to access the Internet at the same time.

Nat and NATP are generally implemented at the gateway, which is transparent to the user.